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VITAMINS & SUPPLEMENTS · GUIDE

Supplements for Brain Fog: What It Is and What Has Been Studied

Brain fog is a description, not a diagnosis. Here is what it can come from, what research on supplements for it shows so far, and why a clinician comes first.

Content last updated . This page has not been medically reviewed.

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See a clinician first

"Brain fog" is a common way to describe trouble with memory, concentration or clear thinking. It is not a diagnosis and it has many possible causes. See a clinician for brain fog that is new, lasting, worsening or affecting work, driving or safety. Sudden confusion needs urgent medical advice (in the US, call 911 in an emergency); see memory and focus: sudden confusion and when to get help. This page is information only, and supplements should not delay finding the cause.

What the term describes

Researchers who reviewed 65 studies of brain fog after long COVID and after chemotherapy found that assessment tools varied widely, and that brain fog was linked with cognitive complaints, fatigue and mood disturbance. [1] In other words, there is no single agreed measure, which makes supplement studies hard to compare.

Conditions where brain fog or poor concentration is listed

The NHS lists these among symptoms of:
  • long COVID: problems with memory and concentration, also called brain fog [2]
  • menopause: mood changes, poor memory and brain fog [3]
  • an underactive thyroid: difficulty concentrating or thinking clearly [4]
  • sleep apnoea: finding it hard to concentrate [5]
  • vitamin B12 or folate deficiency anaemia: problems with memory, understanding and judgment [6]

MedlinePlus adds reactions to certain medicines, and kidney, liver or thyroid problems, as possible causes of forgetfulness. [7] The NHS says to see a GP if you have symptoms of B12 or folate deficiency anaemia, which can be diagnosed with a blood test. [6] See medicines, sleep, mood and illness that affect memory and focus, brain fog: causes and when to check and what vitamin and mineral deficiencies do and do not explain.

What research on supplements shows

Labels: established nutritional role / deficiency treatment, promising but limited, insufficient evidence, no good evidence of benefit.
5 findings · 3 supported · 2 limited or unclearThe colour follows the evidence label on each card.

  1. A supplement for brain fog in general

    Insufficient evidence

    Proper evidence not found. We searched PubMed for brain fog with supplements, systematic reviews and randomized trials, and found no review of nootropics for brain fog.

  2. Long-COVID brain fog

    Promising but limited (one combination, long COVID only)

    A review of 17 studies of interventions, mostly not supplements; two studies of a combination product (PEA-LUT) reported improved cognitive impairment. [8]

  3. Low vitamin B12 or folate

    Established role in deficiency treatment

    Memory and thinking changes are listed symptoms; treatment is clinician-led. [6]

  4. Iron, in people with low iron

    Established role in deficiency treatment; not for others

    Iron improved short-term memory and fatigue in RCTs of non-anemic youth and menstruating adults, but effects were absent without iron deficiency. [9]

  5. Common "memory" ingredients

    Insufficient evidence for brain fog

    A review found no compelling evidence for several, and mixed results for others; it studied memory, not brain fog. [10]

The long-COVID result applies only to people with long COVID and to that specific combination, so it should not be carried over to other people. Fatigue and low mood often go with brain fog, so those are worth raising with a clinician. [1]

Frequently asked questions

Is brain fog a medical condition?

Not by itself. It is a description of symptoms that can come from many causes, so a clinician should check. [1][2]

Which supplement is best for brain fog?

Proper evidence not found. We did not find a systematic review showing any supplement treats brain fog in general. [8]

Can low B12 cause brain fog?

The NHS lists problems with memory, understanding and judgment among symptoms of B12 or folate deficiency anaemia, and advises seeing a GP. [6] See vitamin B12 deficiency.

Does menopause cause brain fog?

The NHS lists poor memory and brain fog among menopause symptoms. [3] A clinician can discuss options.

Can medicines cause foggy thinking?

MedlinePlus lists reactions to certain medicines among possible causes of forgetfulness. [7] Do not stop a prescribed medicine without asking the prescriber.

More details: evidence, limits and cautions

The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.

Limits and uncertainty
  • No agreed definition or test, so a "brain fog" trial may measure very different things.
  • Biomarker or test-score changes are not the same as feeling clearer in daily life.
  • Reviews of memory supplements note a lack of a solid scientific foundation for marketing claims. [10]
  • Supplements may not contain what the label says. [11]
Safety and who should ask first
Do not treat a suspected vitamin or iron problem alone: a blood test and a clinician decide. Iron supplements carry risks, including death in the case of overdose. [12] If a child has swallowed iron or other supplements, call 911 or Poison Help 1-800-222-1222 (US). Supplements can interact with medicines; read how interactions work and quality testing. People who are pregnant, breastfeeding, older, or who have kidney, liver or heart conditions, or are having surgery, should talk to a clinician or pharmacist first. Basics that help many people feel clearer are covered in sleep, food and exercise first.
References
  1. Wilson JC et al. BMJ Ment Health 2025. Brain fog with long covid and chemotherapy: systematic review and meta-analysis. Read 2026-10-23.
  2. NHS (UK), Long-term effects of COVID-19 (long COVID) (page last reviewed 19 August 2025). Read 2026-10-23.
  3. NHS (UK), Menopause: symptoms (page last reviewed 19 May 2026). Read 2026-10-23.
  4. NHS (UK), Underactive thyroid: symptoms (page last reviewed 28 April 2025). Read 2026-10-23.
  5. NHS (UK), Sleep apnoea (page last reviewed 11 May 2026). Read 2026-10-23.
  6. NHS (UK), Vitamin B12 or folate deficiency anaemia: symptoms (page last reviewed 20 February 2023). Read 2026-10-23.
  7. MedlinePlus (US National Library of Medicine), Memory. Read 2026-10-23.
  8. Gorenshtein A et al. Neurol Sci 2024. Intervention modalities for brain fog caused by long-COVID: systematic review of the literature. Read 2026-10-23.
  9. Fiani D et al. Neurosci Biobehav Rev 2025. Psychiatric and cognitive outcomes of iron supplementation in non-anemic children, adolescents, and menstruating adults: a meta-analysis and systematic review. Read 2026-10-23.
  10. Hersant H et al. CNS Drugs 2023. Over the Counter Supplements for Memory: A Review of Available Evidence. Read 2026-10-23.
  11. Crawford C et al. J Altern Complement Med 2021. Dietary Supplement Ingredients for Optimizing Cognitive Performance Among Healthy Adults: A Systematic Review. Read 2026-10-23.
  12. Elliott SD et al. J Neuropsychiatry Clin Neurosci 2024. Iron Supplementation in Management of Neurodevelopmental Disorders: Systematic Review, Meta-Analysis, and Qualitative Synthesis. Read 2026-10-23.
Education, not medical advice. This page is for general information. It does not diagnose or treat any condition and is not a substitute for care from a qualified health professional. Natural does not automatically mean safe. Ask a clinician or pharmacist before changing your care, especially if you take medication, are pregnant or breastfeeding, or have a health condition.