Focus & Memory
Brain Fog: Causes, What Helps and When to Check
Understanding and managing brain fog means working out what is clouding your thinking, then looking after the things that are known to affect clear thinking. Brain fog is a description of how thinking feels, not a diagnosis, so this page helps you look for the cause, shows what research supports and what it does not, and explains when to see a doctor.
General information, not medical advice. Last updated October 31, 2026. Written by the AlternativeMed editorial team. Not medically reviewed.
Start here
- Write down what you notice for one to two weeks: when the fog is worst, your sleep, meals, water, caffeine, stress, and the time you take each medicine or supplement. Bring the notes to a doctor if it does not clear.
- Protect your sleep first. Short sleep is one of the best-documented reasons for slower, less focused thinking, and it is one of the most fixable.
- If the fog is getting in the way of work, driving, managing medicines or daily tasks, or it does not clear, ask a doctor to look for treatable causes such as a medicine side effect, thyroid, B12 or iron problems.
Be careful with
- Brain fog is not a single condition. Sleep loss, stress, low mood, hormonal change, some medicines, long COVID, thyroid or B12 problems and other illnesses can all feel like it. A list of symptoms cannot tell them apart; a clinician and sometimes blood tests can.
- If you suspect a medicine, do not stop it on your own. Track your symptoms and talk to the prescriber or a pharmacist about options.
- No supplement has been shown to clear brain fog in general. Starting iron, B12 or a "brain" blend without a test can hide a cause, delay treatment or cause harm.
- Brain fog is not the same as mild cognitive impairment or dementia, but memory changes that affect daily life still deserve a check.
Get help when
- Sudden confusion, or sudden trouble speaking, understanding, seeing or moving: call your local emergency number or go to emergency care now. Do not drive yourself.
- Brain fog with a severe headache, fever with a stiff neck, a seizure, or confusion after a head injury: seek emergency care now.
- Thoughts of harming yourself, or feeling unable to keep yourself safe: contact local emergency services or a crisis line in your country now.
- Brain fog that is getting worse, interferes with work, driving, managing medicines or daily tasks, or that does not clear: see a doctor.
- Forgetting appointments, trouble completing ordinary tasks, or trouble following a conversation, especially if a family member has noticed.
About Brain Fog: Causes, What Helps and When to Check
What this goal means
This goal is about understanding foggy thinking and taking sensible, evidence-aware steps. Cleveland Clinic describes brain fog as a term for a range of symptoms that affect how clearly you think, focus, concentrate, remember and pay attention. It is usually temporary, but how long it lasts varies.
Because brain fog is a description, the useful question is what is behind it. This page is educational and cannot diagnose you. For the broader habits that support focus, see the Concentration and Think More Clearly goal pages.
1What brain fog can feel like
Cleveland Clinic lists difficulty concentrating or focusing, confusion, fatigue, forgetfulness, losing your train of thought, mental exhaustion, not finding the right words, a slow thought process and reaction time, and trouble paying attention. Everyone describes it a little differently, and it can make routine tasks such as holding a conversation or following instructions harder.
1Common contributing factors
Cleveland Clinic lists a lack of sleep, stress, anxiety or depression, hormonal changes such as pregnancy or menopause, diabetes and low blood sugar, autoimmune conditions such as lupus, multiple sclerosis and fibromyalgia, poor nutrition, and neurodivergent conditions such as ADHD or autism. It can also follow COVID-19 (long COVID), chemotherapy and long hospital stays.
Harvard Health says medicines are a common and often fixable contributor, with sleep aids and pain medicines among the most common. The NHS says an underactive thyroid can cause difficulty concentrating or thinking clearly, and that vitamin B12 or folate deficiency can cause problems with memory, understanding and judgement, some of which can become irreversible if treatment is delayed.
1,2,3,4Brain fog after illness or long COVID
The NHS lists memory and concentration problems, often called brain fog, among the common symptoms of long COVID. A 2024 meta-analysis of 126 studies found that cognitive impairment was still present at a pooled rate of 20% or higher at three months after COVID-19, with a downward trend by 12 months that the authors said needs firmer data. A 2023 meta-analysis found people recovering from COVID-19 scored worse on cognitive tests than healthy controls.
A 2025 review of 65 studies of brain fog after long COVID and chemotherapy found that brain fog was linked with lower cognitive performance, more fatigue and more depressive symptoms, and that the studies used very different measures.
5,6,7,8Realistic expectations
Cleveland Clinic says there is no specific treatment for brain fog itself; care depends on the cause. Where a treatable cause is found, such as a medicine side effect or a thyroid or B12 problem, thinking can improve. Where no single cause is found, steady habits (sleep, activity, regular meals, breaks) are sensible, but research has mostly tested them in healthy people, not in people whose main complaint is brain fog.
Cleveland Clinic says brain fog may last a few days to weeks, and in some cases months to years. Treat any promise to "clear brain fog fast" with caution.
1Is it brain fog, or something else?
Brain fog overlaps with tiredness, low mood and normal forgetfulness. If tiredness is the main problem, see the persistent tiredness and mental fatigue goal pages. If memory is the main concern, see Improve Everyday Memory. The NHS says to see a GP if memory problems affect day-to-day life, because treatment may work better if started early, and it lists stress, anxiety or depression and sleeping problems as common treatable causes. Sudden confusion is a different matter and needs urgent help.
9,10Who this applies to
Brain fog is common after poor sleep or illness, during stressful periods, around pregnancy and menopause, and with some medicines and conditions. It can affect adults of any age. Older adults are more likely to be sensitive to medicine effects: Harvard Health notes a weaker blood-brain barrier, more medicines taken together and slower drug processing as reasons.
1,2Related conditions and symptoms
Thyroid problems and fatigue → Vitamin B12 deficiency → Anemia and iron deficiency → Sleep apnea → Insomnia → Perimenopause and menopause → ADHD in adults → Anxiety disorders → Stress, anxiety, burnout and depression compared → Prediabetes, type 2 diabetes and metabolic syndrome → Mild cognitive impairment and dementia → Forgetfulness and memory loss →
A manageable starting plan
An educational starting point, not a personal prescription. Adjust it to your own situation and any advice from your clinician.
Your first actions
- Keep a one to two week diary of fog, sleep, meals, water, caffeine, stress and medicines.
- Protect sleep with a regular schedule, and drink water through the day.
- Book a visit if the fog lasts, worsens or affects daily life, and bring the diary and a full medicine and supplement list.
- Do not stop any prescribed medicine on your own; ask about a review instead.
Optional additions
- Add regular activity, building up slowly, if it leaves you feeling better rather than worse.
- Try a structured mindfulness or relaxation habit if stress is part of the picture.
- Move toward a Mediterranean-style eating pattern, with regular meals.
- Keep a notebook for tasks and appointments and take short breaks between demanding tasks.
What to track
- Fog level morning, midday and evening, and what happened before it eased or worsened.
- Sleep times, naps, caffeine, alcohol, meals and water.
- When any medicine or supplement was started or changed.
- Mood, stress and any new symptoms such as weight change, breathlessness or low energy.
When to reassess
Check again after one to two weeks of steady habits and diary notes. If the fog has not eased, is getting worse, or interferes with work, driving or managing medicines, see a clinician. Return sooner for any warning sign.
When to seek professional support
- See a doctor or nurse if brain fog lasts or affects daily life; ask about medicines, thyroid, B12 and iron checks.
- Ask a pharmacist to review your medicines and supplements.
- Call emergency services for sudden confusion, severe headache with fever and stiff neck, or after a head injury.
- If you feel low or unable to keep yourself safe, contact a crisis line or emergency services in your country now.
What helps
Ordered by how well the research supports each step. Evidence strength is shown on every card; precautions sit next to the advice.
Start here
Keep a simple symptom and medicine diary for one to two weeks
Low certaintyAddresses: Helps you and a clinician spot patterns and possible causes
Why it may help: Harvard Health advises tracking symptoms for one to two weeks and sharing them with your doctor if you suspect a medicine: when you take it, with or without food, what kind of memory or thinking problems you notice, how long they last and when they tend to appear. The same habit helps with other causes, such as sleep, meals and stress.
How to apply it: Use a notebook or phone note. Each day, jot down when the fog was worst, hours slept, meals, water, caffeine, alcohol, stress, and the time you took each medicine or supplement.
Who it may suit: Anyone with brain fog that lasts more than a few days or keeps coming back.
Precautions: A diary does not diagnose anything. It is a tool for a conversation with a clinician, not a reason to change a prescribed medicine.
2,1Medicines, sleep, mood and illness that affect memory → Talking with a health professional →
Protect your sleep
Low certaintyAddresses: Steadier attention and less mental slowness
Why it may help: A 2010 meta-analysis of 70 articles on short-term total sleep loss in healthy adults found the largest effect on lapses in simple attention (g -0.776). A 2024 meta-analysis of 44 studies found that one night of 2 to 6 hours of sleep raised sleepiness and impaired sustained attention. These were laboratory studies of deliberate sleep loss in healthy adults, so they show that lost sleep hurts attention, not that fixing sleep clears long-standing brain fog.
How to apply it: Aim for a regular bedtime and wake time, a dark, cool, quiet room, and a wind-down routine. Our sleep pages cover this in detail.
Who it may suit: Anyone whose fog is worse after short or broken sleep.
Precautions: If you snore loudly, gasp at night or stay very sleepy in the day, ask a doctor about sleep apnea rather than only trying habits. If sleep problems last, ask for help.
11,12,1Ask a doctor to look for treatable causes if the fog lasts or interferes with daily life
Moderate certaintyAddresses: Finds a cause you can actually treat
Why it may help: Cleveland Clinic says a healthcare provider can help work out what is behind brain fog, and to contact one if it interferes with quality of life, for example if you forget appointments or struggle with ordinary tasks. The NHS describes blood tests for an underactive thyroid and for B12 or folate deficiency, and the NHS says memory problems that affect day-to-day life should be seen by a GP because some causes are common and treatable.
How to apply it: Book a visit and bring your diary and a list of every medicine and supplement you take, including over-the-counter sleep aids and pain relievers.
Who it may suit: Anyone whose brain fog lasts, worsens or affects work, driving, medicines or daily tasks.
Precautions: A normal result does not mean the fog is not real. Ask what happens next and return if it continues or changes.
1,3,4,9Thyroid problems and fatigue → Vitamin B12 deficiency → Memory changes: when to get help →
Write things down and take short breaks
Low certaintyAddresses: Takes load off an overworked mind while the fog lasts
Why it may help: Cleveland Clinic lists writing down important information so you do not forget it, and taking short breaks through the day to avoid overworking your brain, among the first steps a clinician may suggest. These are practical coping steps; no trial read tested them as a treatment for brain fog.
How to apply it: Keep one list or notebook for tasks and appointments. Take short breaks away from screens between demanding tasks.
Who it may suit: Anyone finding that ordinary tasks feel harder than usual.
Precautions: These steps help you cope; they do not replace finding the cause of persistent fog.
1Additional options
Regular physical activity
Low certaintyAddresses: Small gains in thinking in healthy people
Why it may help: Cleveland Clinic lists about 30 minutes of physical activity a day among the first steps a clinician may suggest. A 2023 meta-analysis of 54 randomized trials in healthy children, adults and older adults found exercise benefited overall cognition and every cognitive domain tested, with the greatest benefits for older adults; the authors said more studies are needed on attention and information processing. The trials were not in people with brain fog.
How to apply it: Start with something you already enjoy, such as walking, and build slowly. Mind-body exercise showed benefit for memory in the review.
Who it may suit: Most adults without a condition that limits activity.
Precautions: If you are recovering from long COVID or feel much worse after effort, build up activity only with a care team's guidance. If you have a heart, lung or joint condition, or are new to exercise, ask a clinician first.
13,1,14Drink enough water
Low certaintyAddresses: Avoids a small, measurable drop in attention
Why it may help: A 2018 meta-analysis of 33 studies (413 people) found that deliberate dehydration, mostly 1% to 6% body-mass loss, slightly impaired cognitive performance (effect size -0.21), most for attention (-0.52) and executive function (-0.24), and more when body-mass loss was over 2%. Everyday mild thirst was not studied.
How to apply it: Drink when thirsty and through hot or active days, and keep a glass of water where you work.
Who it may suit: Anyone whose fog is worse on hot, busy or poorly hydrated days.
Precautions: People on fluid limits for heart, kidney or liver conditions should follow their care team's advice.
15Online CBT and supervised rehabilitation after long COVID
Moderate certaintyAddresses: Better concentration and overall health in long COVID
Why it may help: A 2024 BMJ living systematic review of 24 trials (3,695 adults with long COVID) found moderate-certainty evidence that an online cognitive behavioural therapy (CBT) programme probably improves concentration (mean difference -5.2 on a concentration-problems scale) and reduces fatigue compared with usual care, and that an online supervised programme combining physical and mental health rehabilitation probably improves overall health. The NHS lists cognitive rehabilitation, activities to improve memory, concentration, thinking and mood, as part of long COVID care.
How to apply it: Ask your GP or long COVID service what is available. The programmes in the trials were structured and supervised.
Who it may suit: People whose brain fog began after COVID-19.
Precautions: The finding applies to people with long COVID, not to brain fog from other causes. If effort makes you feel worse, tell the care team before increasing activity.
14,5Mindfulness courses
Low certaintyAddresses: Small-to-moderate gains in attention and working memory
Why it may help: A 2024 meta-analysis of 111 randomized trials (9,538 people) found mindfulness courses had small-to-moderate effects on global cognition, executive attention, working memory accuracy, sustained attention and subjective cognitive functioning, and no effect on processing speed or episodic memory. Effects were larger in people with raised psychiatric symptoms. Brain fog itself was not the outcome.
How to apply it: Look for a structured course with a trained teacher, or start with a few minutes of guided practice.
Who it may suit: People who find stress or a busy mind part of their fog.
Precautions: Some people find meditation uncomfortable when anxious or after trauma; go gently and stop if it increases distress, and talk to a clinician if it does.
16Meditation and mindfulness → Mindfulness and meditation for stress →
Mediterranean-style eating
Low certaintyAddresses: Better thinking scores in older adults over several years
Why it may help: In a Spanish randomized trial of 447 cognitively healthy older adults at high cardiovascular risk, those assigned a Mediterranean diet with olive oil or nuts scored better on some memory and attention tests after a median of 4.1 years, while the control group's scores fell. This was an older, higher-risk group, and brain fog was not measured.
How to apply it: Build meals around vegetables, fruit, legumes, whole grains, fish, nuts and olive oil. The trial gave olive oil or nuts to participants; those amounts are not advice.
Who it may suit: Most adults who want a long-term, food-based approach.
Precautions: Nuts are a risk for people with nut allergy. People with diabetes or on blood-sugar medicines should check with their care team before big diet changes.
17,1Still being studied
Palmitoylethanolamide with luteolin (PEA-LUT) for long COVID brain fog
Very low certaintyAddresses: Reported improvement in cognitive impairment in two small studies
Why it may help: A 2024 systematic review of 17 studies of interventions for long COVID brain fog reported that two studies of this combination supplement found improved cognitive impairment. The review did not grade certainty in its abstract, and the studies were few and small.
How to apply it: Not recommended here. It is described only so you know what has been studied.
Who it may suit: Only people with long COVID, and only after talking with a clinician.
Precautions: The 2024 BMJ review found no compelling evidence for several supplements it examined (including coenzyme Q10 and a probiotic-prebiotic combination). Supplements can interact with medicines; ask a pharmacist.
18,14Vitamin D, when your level is low
Low certaintyAddresses: A small gain in overall thinking in trials
Why it may help: A 2024 meta-analysis of 24 randomized trials (7,557 people, mean age about 65) found vitamin D supplements had a small positive effect on global cognition (Hedges' g 0.128), larger in people who were vitamin D deficient at the start (g 0.480). It did not affect specific cognitive domains. Brain fog was not the outcome.
How to apply it: Ask a clinician about a blood test. The trial authors suggested correcting a deficiency rather than supplementing everyone.
Who it may suit: People whose clinician has found a low vitamin D level.
Precautions: Too much vitamin D can be harmful, so take it only on a clinician's advice.
19Specialist treatments studied in small long COVID studies (brain stimulation, hyperbaric oxygen)
Very low certaintyAddresses: Improved test scores in small studies
Why it may help: The same 2024 review of 17 studies reported that six studies of noninvasive brain stimulation and three of hyperbaric oxygen therapy showed improvements in cognitive tests, but the studies were small and varied. The larger 2024 BMJ review of randomized trials found no compelling evidence for hyperbaric oxygen or transcranial direct current stimulation.
How to apply it: These are specialist treatments delivered in clinical settings and are not something to try on your own.
Who it may suit: Only people with long COVID, in a clinical or research setting.
Precautions: Ask your care team about evidence, risks and cost before considering any such treatment.
18,14Food & nutrition
Eating regularly and well
Cleveland Clinic lists poor nutrition as a possible cause of brain fog and eating healthy, nutritious meals as one of the first steps a clinician may suggest. It also lists diabetes and low blood sugar among the causes, so people with diabetes should follow their care team's advice about meals and medicines.
No trial read tested a particular meal pattern in people whose main problem is brain fog. Regular meals are a sensible base, not a proven cure.
A Mediterranean-style eating pattern
Low certaintyAddresses: Supports long-term thinking health
Why it may help: In the Spanish trial of 447 older adults, those given a Mediterranean diet with olive oil or nuts had better memory, frontal (attention and executive) and global cognition scores than a control diet group after a median of 4.1 years. The control group's scores fell.
How to apply it: Vegetables, fruit, legumes, whole grains, fish, nuts and olive oil, with regular meals.
Who it may suit: Most adults; the trial was in older adults at high cardiovascular risk.
Precautions: Nut allergy; people with diabetes should check with their care team.
17Water, caffeine and alcohol
Mild dehydration slightly lowers attention in experiments, so regular drinking is a simple habit to keep. The FDA cites 400 mg of caffeine a day as generally not linked to negative effects in healthy adults, but says sensitivity varies and that too much can cause jitters, anxiety and poor sleep.
People who are pregnant, trying to become pregnant or breastfeeding, and those with certain conditions or medicines, are advised by the FDA to talk with their provider about limiting caffeine.
15,20Nutrients that matter when they are low
Low thyroid hormone, B12 or folate, iron and vitamin D are the nutrient-related problems linked to foggy thinking in the sources read. Each is checked with a blood test, and food or supplements help mainly when a low level is found. See the linked pages for food sources and for what to ask a clinician.
4,21,19Remedies & supplements
Traditional use, laboratory findings and human trials are kept apart. "Natural" does not mean safe.
Vitamin B12 and folate (for proven deficiency)
Not enough evidenceStudied form and route: Tablets or injections prescribed by a clinician
Intended outcome: Treats memory and judgement problems caused by deficiency
Human evidence: The NHS lists problems with memory, understanding and judgement as symptoms of B12 or folate deficiency anaemia, diagnosed by a blood test, and says some problems can become irreversible if treatment is delayed. A Cochrane review of B12 for cognition found that, in people with dementia and low B12, evidence of benefit was insufficient; no trials in people without dementia were found.
Traditional use: No traditional-use claim is relevant here.
Laboratory findings: No laboratory work was needed for this page.
Limits: Benefit is established for treating deficiency. For people who are not deficient, there is no evidence that extra B12 clears brain fog.
Interactions and precautions: Do not guess: get tested. Nerve symptoms need assessment. Some medicines can affect B12 absorption; do not stop them without advice.
4,22Iron (for proven low iron)
Low certaintyStudied form and route: Tablets prescribed or recommended after a blood test
Intended outcome: Improved short-term memory and fatigue in iron-deficient people
Human evidence: A 2025 meta-analysis of 18 studies (1,408 participants, mostly menstruating adults) of iron supplementation in people without anaemia found improved fatigue, anxiety, physical well-being, cognitive intelligence and short-term memory in randomized trials, but not attention or depression. The benefit was in people who were iron deficient.
Traditional use: No traditional-use claim is relevant here.
Laboratory findings: No laboratory work was needed for this page.
Limits: The review covered children, teenagers and menstruating adults. It does not show iron helps people with normal iron.
Interactions and precautions: Iron supplements carry risks including death in the case of overdose, so keep them away from children. Take them only after a blood test and clinician advice.
21,23Vitamin D (for a low level)
Low certaintyStudied form and route: Supplement on clinician advice
Intended outcome: Small gain in global thinking, mainly in deficient people
Human evidence: A 2024 meta-analysis of 24 randomized trials found a small positive effect on global cognition (g 0.128), stronger in people with baseline deficiency (g 0.480) and in vulnerable populations. Participants were mostly older adults (mean age about 65).
Traditional use: No traditional-use claim is relevant here.
Laboratory findings: No laboratory work was needed for this page.
Limits: Brain fog was not measured, and the trials were mostly in older adults.
Interactions and precautions: Too much vitamin D can harm; get a blood test and clinician advice first.
19Omega-3 fish or algae oil
Evidence againstStudied form and route: Capsules or liquid
Intended outcome: No clear benefit for thinking in healthy people
Human evidence: A 2015 meta-analysis of 24 trials found no improvement in cognitive performance in healthy people or in people with ADHD and related conditions, other than short-term memory in those with low omega-3 status. A 2012 Cochrane review of three trials in cognitively healthy people aged 60+ found no difference on cognitive tests; the main side effect was mild stomach upset, and minor adverse events occurred in fewer than 15% of participants.
Traditional use: No traditional-use claim is relevant here.
Laboratory findings: No laboratory work was needed for this page.
Limits: Neither review tested brain fog.
Interactions and precautions: No interaction study was read here; absence of a study is not proof of safety. People who take blood thinners can ask a pharmacist before starting.
24,25Caffeine (coffee, tea, supplements)
Not enough evidenceStudied form and route: Drinks, tablets or added to products
Intended outcome: Short-term alertness for many; effect on brain fog is not established
Human evidence: No study of caffeine and brain fog was read. The FDA cites 400 mg a day as an amount not generally linked to negative effects in healthy adults.
Traditional use: Coffee and tea are widely used for alertness.
Laboratory findings: Not covered by the sources read.
Limits: Sensitivity varies widely, and caffeine can worsen anxiety and sleep, which can worsen fog.
Interactions and precautions: Pregnancy, breastfeeding, anxiety, sleep problems and some medicines: talk to a provider. Energy drinks are not advised for children and teens.
20Herbal "nootropics": ginkgo, bacopa, ginseng, rhodiola
Mixed findingsStudied form and route: Extracts, capsules and blends
Intended outcome: Mixed and uncertain; not tested for brain fog
Human evidence: A 2021 systematic review of nine ingredients in healthy adults, including bacopa, ginkgo, ginseng and rhodiola, found studies inconsistent, imprecise and often methodologically flawed, so the authors could not make recommendations. A 2023 review found mixed results for ginkgo and some evidence for memory benefit with ashwagandha, curcumin, turmeric and ginger.
Traditional use: Several have long traditional uses for memory or stamina; this is not human trial evidence.
Laboratory findings: Not covered by the sources read.
Limits: The reviews tested healthy adults or memory, not brain fog. Product contents are not always as labelled.
Interactions and precautions: Herbs can interact with medicines. No interaction study was read here, so absence of a warning is not proof of safety. Ask a pharmacist, and avoid in pregnancy and breastfeeding unless a clinician agrees.
26,27Lion's mane and other supplements marketed for memory (creatine, choline, tyrosine)
Very low certaintyStudied form and route: Mushroom extracts and powders, capsules
Intended outcome: Some early memory findings; nothing for brain fog
Human evidence: The 2023 review of over-the-counter memory supplements reported some evidence of memory benefit for lion's mane and choline and no compelling evidence for several others, but the studies were mixed and short. The 2021 review included creatine, choline and tyrosine and found the certainty low.
Traditional use: Lion's mane is used in traditional cuisine and medicine in East Asia.
Laboratory findings: Not covered by the sources read.
Limits: No trial was read in people whose main complaint is brain fog.
Interactions and precautions: Allergy is possible with mushroom products. Ask a pharmacist about medicines and conditions.
27,26Therapies & care
Established professional care for brain fog starts with finding the cause and treating it. This page does not recommend medicines or doses, and you should not stop a prescribed medicine on your own. Care may include a medicine review, treatment of a thyroid, B12 or iron problem, sleep or stress care, talking therapy, or rehabilitation after illness.
Medical assessment and medicine review
Moderate certaintyConventional care A clinician asks about symptoms, sleep, mood and medicines, and may arrange blood tests such as thyroid tests or a B12 and folate blood test. Cleveland Clinic and the NHS say care depends on the cause.
Who it may suit: Anyone whose fog lasts, worsens or affects daily life.
Precautions: Take your diary and medicine list.
1,3,4,2Cognitive behavioural therapy (CBT)
Moderate certaintyTalking therapy Cleveland Clinic lists psychotherapy such as CBT among the first-line steps. The 2024 BMJ review found moderate-certainty evidence that an online CBT programme probably improves concentration in long COVID.
Who it may suit: People with long COVID; also those whose fog goes with stress, low mood or anxiety.
Precautions: Choose a trained, registered practitioner. Anxiety and mood problems have their own care pages.
1,14Cognitive rehabilitation and supervised rehabilitation
Low certaintyRehabilitation The NHS lists cognitive rehabilitation, which uses activities to improve memory, concentration, thinking and mood, as part of long COVID support. The BMJ review found moderate-certainty evidence that an online supervised programme combining physical and mental health rehabilitation probably improves overall health.
Who it may suit: People recovering from long COVID or another illness.
Precautions: No trial result for cognitive rehabilitation itself was read here. Build up activity only with the care team's guidance.
5,14Sleep care, including CBT for insomnia
Not enough evidenceSleep treatment Poor sleep is a leading everyday contributor to foggy thinking. Our sleep pages cover structured treatments such as CBT for insomnia and when to check for sleep apnea.
Who it may suit: People whose fog goes with poor or unrefreshing sleep.
Precautions: No trial read tested sleep treatment on brain fog itself.
11,1Mindfulness-based programmes
Low certaintyMind-body practice Mindfulness courses showed small-to-moderate gains on attention and working memory across 111 trials.
Who it may suit: People who find stress part of the picture.
Precautions: Go gently if meditation increases anxiety or distress.
16What to avoid
Habits, products and claims that can get in the way. Never stop a prescribed medicine without talking to the professional who prescribed it.
Risks that apply to most people
Stopping or changing a prescribed medicine on your own because you think it is causing fog
Moderate certaintyWhy: Harvard Health says not to stop a medicine on your own. Track your symptoms for one to two weeks and share the results with your doctor, who may switch the medicine, change the dose, or change the timing.
Who it applies to: Anyone taking a prescribed medicine.
Try instead: Keep taking it as prescribed and book a medicine review with your prescriber or pharmacist.
2Waiting it out when the fog is getting worse or is affecting daily life
Moderate certaintyWhy: Cleveland Clinic says to let a provider know if brain fog is disruptive, and the NHS says to get memory problems that affect daily life checked because treatment may work better if started early.
Who it applies to: Anyone whose fog is lasting, worsening or affecting work, driving, medicines or safety.
Try instead: Book a visit and bring your diary and medicine list.
1,9Personal triggers to check
Short or broken sleep
Moderate certaintyWhy: Meta-analyses in healthy adults found that short-term sleep loss impaired attention, and that even one night of 2 to 6 hours of sleep raised sleepiness and attention lapses.
Who it applies to: Anyone, especially during busy or stressful periods.
Try instead: Protect a regular sleep window and ask for help if sleep stays poor.
11,12Dehydration
Low certaintyWhy: A 2018 meta-analysis of 33 studies found deliberate dehydration slightly impaired cognitive performance, most clearly for attention and executive function.
Who it applies to: Hot days, long work stretches, illness with fluid loss, or exercise without drinking.
Try instead: Drink regularly through the day.
15Too much caffeine, or caffeine late in the day
Not enough evidenceWhy: The FDA cites 400 mg of caffeine a day as an amount not generally linked to negative effects in healthy adults, but says too much can cause jitters, anxiety and sleep problems, and that sensitivity varies widely. Poor sleep and anxiety can worsen foggy thinking. No study of caffeine and brain fog was read.
Who it applies to: People who feel anxious, sleep badly, are pregnant or breastfeeding, or are sensitive to caffeine; some medicines also raise sensitivity.
Try instead: Notice how caffeine affects your sleep and fog in your diary, and talk to a clinician if you are pregnant, breastfeeding or on medicines.
20Medicines that can cloud thinking, especially in older adults
Moderate certaintyWhy: Harvard Health names over-the-counter sleep aids containing an antihistamine with anticholinergic properties, some prescription sleep drugs and several pain medicines as common culprits for confusion and memory problems, and says anticholinergic drugs are well known to impair thinking in older people.
Who it applies to: Older adults, people taking several medicines, and anyone who noticed fog after starting or changing a medicine.
Try instead: Do not stop anything on your own; ask the prescriber or a pharmacist about alternatives, timing or dose.
2Products that need caution
"Brain fog" or memory supplement blends
Low certaintyWhy: A 2023 review of over-the-counter memory supplements found no compelling evidence for several common ingredients and mixed or limited evidence for others, and noted the industry lacks a solid scientific foundation for its marketing claims. A 2021 systematic review of nine popular single ingredients in healthy adults found the evidence inconsistent and often flawed, and noted that products do not always contain what the label says. Neither studied brain fog as such.
Who it applies to: Anyone considering a nootropic or memory blend.
Try instead: Find the cause first; if you still want to try something, check the ingredient list with a pharmacist and read our interactions page.
27,26Iron or B12 tablets taken without a test
Moderate certaintyWhy: Iron and B12 problems are diagnosed with blood tests (NHS), so supplements taken first can hide a cause or delay treatment. A 2025 review found iron helped short-term memory only in iron-deficient people, and a 2024 review notes iron supplementation carries risks, including death in the case of overdose.
Who it applies to: Anyone tempted to try supplements for fog.
Try instead: Ask for a blood test first, and keep iron tablets out of reach of children.
4,21,23Energy drinks and stimulants to push through the fog
Low certaintyWhy: The FDA notes that sensitivity to caffeine varies, that too much can cause jitters, anxiety and poor sleep, and that medical experts advise against energy drinks for children and teens.
Who it applies to: Anyone using them to stay alert.
Try instead: Look at sleep, meals, water and medicines first.
20Unsupported claims
"This supplement clears brain fog"
Evidence againstWhy: A 2024 BMJ review found no compelling evidence for several supplements tested in long COVID (including coenzyme Q10), and the supplement reviews read here did not test brain fog itself. Cleveland Clinic says there is no specific treatment for brain fog.
Who it applies to: Product pages and social posts promising a fast fix.
Try instead: Treat the cause, and use evidence-aware habits.
1,14,27"Omega-3 supplements sharpen your thinking"
Evidence againstWhy: A 2015 meta-analysis of 24 trials found omega-3 supplements did not improve cognitive performance in healthy people or in people with ADHD and related conditions, though short-term memory improved in those with low omega-3 status. A 2012 Cochrane review of three trials in cognitively healthy older people found no difference in cognitive tests.
Who it applies to: Fish oil and algae oil marketing.
Try instead: Focus on the overall eating pattern and treat any proven deficiency.
24,25"Brain fog means dementia"
Moderate certaintyWhy: Cleveland Clinic describes brain fog as symptoms with many possible causes, usually temporary. The NHS says memory loss can have common treatable causes such as stress, anxiety or depression, and sleeping problems, and occasionally signals something more serious, so a GP should check persistent problems.
Who it applies to: Anyone worried after a few foggy weeks.
Try instead: Get persistent or worsening change checked rather than self-diagnosing.
1,9Mild cognitive impairment and dementia → Forgetfulness and memory loss →
Common mistakes
Treating sudden confusion as ordinary brain fog
High certaintyWhy: The NHS says that sudden confusion needs immediate medical help, as many causes need to be assessed and treated as soon as possible and may be life threatening.
Who it applies to: Anyone, or a person they are looking after, who becomes suddenly confused.
Try instead: Call your local emergency number or go to emergency care; do not drive yourself.
10Pushing hard through exercise or work when effort leaves you much worse afterwards
Not enough evidenceWhy: The 2024 BMJ review found benefit for supervised programmes after long COVID, but the sources read do not give details on safe pacing, so none is stated here.
Who it applies to: People recovering from long COVID or other illness.
Try instead: Ask the care team how to build up activity.
14Blaming age or stress without checking
Low certaintyWhy: Harvard Health warns that older adults may shrug off foggy spells as senior moments when medicines may be the real culprit.
Who it applies to: Older adults and their families.
Try instead: Review medicines and get basic causes checked.
2Evidence & safety
What the research shows
Health agencies agree that brain fog is a description of symptoms with many possible causes, that there is no specific treatment for brain fog itself, and that care depends on the cause. The best-supported help found is an online CBT programme and supervised rehabilitation after long COVID (moderate certainty, from a 2024 BMJ living review). Sleep, activity, hydration, mindfulness and a Mediterranean-style diet are sensible but have low-certainty evidence for brain fog, because they were tested in healthy people or older adults, not in people whose main problem is brain fog. Supplements help mainly when a deficiency is proven; omega-3 shows no benefit in healthy people.
Limits of the evidence
- Brain fog has no agreed definition or test, so studies measure different things.
- No trial read tested sleep improvement, exercise, mindfulness, hydration, vitamin D, B12, iron, diet pattern or caffeine in people whose main complaint is brain fog.
- Most sleep, exercise, hydration and mindfulness reviews were of healthy people in short or laboratory studies.
- The PEA-LUT, brain stimulation and hyperbaric oxygen findings come from small studies in a 2024 review; the larger BMJ review found no compelling evidence for several of these.
- The NHS, Cleveland Clinic, Harvard Health and FDA pages were summarised by a tool and a page reader; wording here is paraphrased, and those pages carry no named reviewer on this site.
Precautions and interactions
- Do not stop any prescribed medicine without advice from the prescriber.
- Supplements and herbs can interact with medicines; no interaction study was read for several of them here, and absence of a study is not proof of safety.
- Iron tablets can be fatal to young children in overdose; store them out of reach.
- Natural does not mean safe; ask a pharmacist or doctor before adding supplements, especially with a health condition.
Life-stage considerations
- Pregnancy and breastfeeding: pregnancy and menopause are listed as hormonal causes of brain fog. The FDA advises talking with your provider about limiting caffeine, and supplements and herbs should be cleared with a midwife or doctor.
- Menopause and hormonal change: the NHS lists brain fog among symptoms; raise it with a clinician.
- Older adults: medicines are more likely to contribute, and Harvard Health notes older adults are more sensitive to drug effects. New or progressive memory change needs a check.
- Children and teenagers: the reviews here were in adults; speak to a paediatrician about persistent thinking or concentration problems and do not give supplements or herbs without advice.
- People with chronic conditions: diabetes and low blood sugar, autoimmune conditions, thyroid problems and long COVID can all contribute; manage them with your care team.
Warning signs
- Sudden confusion, or sudden trouble speaking, understanding, seeing or moving.
- Brain fog with a severe headache, fever with a stiff neck, a seizure, or confusion after a head injury.
- Thoughts of harming yourself, or feeling unable to keep yourself safe.
- Fog that is getting worse or that stops you working, driving or managing medicines.
- Progressive memory loss or personality change noticed by others.
Claim checks
There is a supplement that treats brain fog
Evidence againstCleveland Clinic says there is no specific treatment for brain fog. The reviews read found no compelling evidence for several supplements in long COVID and no review showing a supplement treats brain fog in general.
1,14,27Omega-3 improves thinking
Evidence againstTwo reviews found no cognitive improvement from omega-3 in healthy adults or cognitively healthy older people.
24,25Lack of sleep causes foggy thinking
Moderate certaintyMeta-analyses in healthy adults found that short-term sleep loss impaired attention, with the largest effect on lapses in simple attention. Whether fixing sleep clears persistent brain fog was not tested.
11,12Medicines can cause brain fog
Moderate certaintyHarvard Health, an expert health publication, says medicines are a common, often fixable contributor, especially sleep and pain medicines in older adults. It is expert guidance rather than a trial.
2Online CBT helps brain fog after long COVID
Moderate certaintyA 2024 BMJ living review found moderate-certainty evidence that an online CBT programme probably improves concentration compared with usual care. It applies to long COVID only.
14Exercise clears brain fog
Low certaintyA review of 54 trials found exercise benefited thinking in healthy people. It was not tested in people with brain fog.
13Mindfulness clears brain fog
Low certaintyA review of 111 trials found small-to-moderate gains in attention and working memory. Brain fog was not the outcome.
16Drinking more water clears brain fog
Low certaintyDeliberate dehydration slightly impaired attention in experiments. Everyday mild thirst and brain fog were not studied.
15Iron or B12 pills fix foggy thinking
Not enough evidenceThey help when a deficiency is proven. Iron improved short-term memory in iron-deficient people only, and evidence for B12 on thinking in people without deficiency is insufficient.
21,22,4Questions people ask
Is brain fog a medical condition?
No, it is a term for a range of symptoms rather than a diagnosis. Cleveland Clinic says a healthcare provider can help work out the underlying cause.
What causes brain fog?
Cleveland Clinic lists lack of sleep, stress, anxiety or depression, hormonal changes, diabetes and low blood sugar, autoimmune conditions, poor nutrition, ADHD or autism, long COVID, chemotherapy and long hospital stays. Harvard Health adds that sleep and pain medicines are common culprits.
How long does brain fog last?
Cleveland Clinic says it varies: a few days to weeks for many people, and months to years in some cases, depending on the cause.
Is there a treatment for brain fog?
There is no specific treatment for brain fog itself; care depends on the cause. A clinician often starts with better sleep habits, nutritious meals, daily physical activity, writing things down, short breaks and sometimes CBT.
How common is brain fog after COVID-19?
A 2024 meta-analysis of 126 studies found cognitive impairment was still present at a pooled rate of 20% or higher at three months after COVID-19, trending down by 12 months, though firmer data are needed.
What helps brain fog after long COVID?
A 2024 BMJ living review of 24 trials found moderate-certainty evidence that an online CBT programme probably improves concentration, and that supervised online rehabilitation probably improves overall health. The NHS lists cognitive rehabilitation as a possible support.
Can lack of sleep cause brain fog?
Yes, it is a listed cause. Meta-analyses in healthy adults found short-term sleep loss worsens attention, and even one short night raised sleepiness and attention lapses.
Can my medicines be causing it?
They can. Harvard Health names over-the-counter sleep aids, some prescription sleep drugs and some pain medicines. Do not stop a medicine on your own; track symptoms for one to two weeks and discuss with your doctor.
Can thyroid, B12 or iron problems cause brain fog?
They can contribute. The NHS lists trouble concentrating with an underactive thyroid and memory and judgement problems with B12 or folate deficiency. A blood test checks them. Iron helped short-term memory only in people who were iron deficient.
Do omega-3, vitamin D or other supplements clear brain fog?
The evidence is thin. Two reviews found omega-3 did not improve thinking in healthy adults or older people, and a 2024 review found a small benefit from vitamin D, larger in deficient people. Brain fog itself was not the outcome.
Does brain fog mean dementia?
Not by itself; many other causes exist. The NHS says to see a GP if memory problems affect day-to-day life, because treatment may work better if started early.
When should I see a doctor?
Cleveland Clinic says to contact a provider if brain fog interferes with your quality of life, for example if you forget appointments or cannot complete ordinary tasks. Sudden confusion needs emergency help.
References
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- Harvard Health Publishing. Stuck in a brain fog? Look in your medicine cabinet (1 October 2021). Read 2026-10-31. source
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- NHS. Vitamin B12 or folate deficiency anaemia. Read 2026-10-31. source
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- NHS. Memory loss (amnesia) (page last reviewed 9 October 2023). Read 2026-10-31. source
- NHS. Sudden confusion (delirium) (page last reviewed 28 May 2024). Read 2026-10-31. source
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- US Food and Drug Administration. Spilling the Beans: How Much Caffeine is Too Much? Read 2026-10-31. source
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Related on AlternativeMed
Related goals
Improve Your Concentration → Think More Clearly → Stay Focused for Longer → Manage Distractions → Improve Everyday Memory → Maintain Brain Health as You Age → Reduce Mental Fatigue → Improve Your Sleep Quality → Stay Hydrated for Daily Wellbeing →
Ingredients, foods and supplements
Nootropics and memory supplements → Supplements for brain fog: what has been studied → Vitamins and minerals for memory and brain fog → Caffeine and energy drinks →
Research, safety and claim-check resources
Memory changes: when to get help → Medicines, sleep, mood and illness that affect memory → Do brain training games work? → Foods for brain health → Sleep hygiene → Meditation and mindfulness → How interactions work → Talking with a health professional → Sleep, food and exercise first →