Supplements for Students and Exam Performance: What Is Known
What trials and reviews show about caffeine, L-theanine and other supplements for studying and exams, what they cannot show, and why sleep and safety come first.
Content last updated . This page has not been medically reviewed.
Quick answer
Most of the research on "study supplements" is about caffeine, sometimes paired with L-theanine, and it measures short lab tasks such as reaction time or switching attention. Almost none of it measures exam results or grades. This page is information only. It is not advice about what to take, and it does not cover non-prescribed stimulant medicines, which have their own page: non-prescribed stimulant use in students.
How to read the evidence here
Labels used on this page: evidence in adequately nourished people (trials in healthy adults), promising but limited, mixed, insufficient evidence, no good evidence of benefit and marketing claim. A lab task is not an exam. A result from sleep-deprived adults is not a result for rested students. Study amounts below are what researchers tested, never advice.What research has found
| Question | What the source found | Label |
|---|---|---|
| Does caffeine affect attention? | A systematic review of plant-derived nootropics concluded that caffeine enhances attention and executive functions. [1] | Promising but limited (lab tasks) |
| Does L-theanine plus caffeine help? | A review of 50 randomized trials in healthy people (15 usable for pooling) found small-to-moderate differences in the first two hours, and the authors say the confidence intervals showed uncertainty in direction and size. [2] | Mixed |
| One small crossover trial | A combination of L-theanine (97 mg) and caffeine (40 mg) versus placebo improved attention on a switching task, but not subjective alertness or intersensory attention. [3] | Promising but limited |
| Sleep-deprived young adults | In 37 healthy adults aged 22-30 who had stayed up overnight, a 200 mg L-theanine and 160 mg caffeine combination improved accuracy and speed on a traffic-scene attention task. [4] | Limited: one lab task, one night |
| Single supplement ingredients for healthy adults | A systematic review found the science low in certainty, with studies inconsistent, imprecise and often flawed. [5] | Insufficient evidence |
| Do any supplements raise exam grades? | Proper evidence not found. We searched PubMed for trials of caffeine, supplements or "nootropics" with exam or academic outcomes in students and found surveys and one cross-sectional study, not controlled trials. | Insufficient evidence |
The cross-sectional study of 403 medical students found small negative links between coffee and tea intake and self-reported grades. [6] That kind of study cannot show cause and effect, and it says nothing about supplements.
Sleep comes first
A meta-analysis of 44 studies found that a single night of restricted sleep can increase sleepiness and impair sustained attention. [7] Caffeine can feel like a fix, but the trial above tested people who were already sleep-deprived, not a plan for exam weeks. For study habits see focus habits for study, and for the main caffeine guide see caffeine supplements.Frequently asked questions
Do study supplements improve exam scores?
Proper evidence not found. The trials we read measured lab tasks, not exam results. [2][5]
Is caffeine the only studied option?
It is the most studied. A review of plant-derived nootropics reported that caffeine enhances attention and executive functions, with inconsistencies for other plants. [1]
Does L-theanine plus caffeine work better than caffeine alone?
The sources we read do not settle it. One small trial found a task-switching benefit but no change in subjective alertness. [3] A larger review reported uncertain direction and size. [2]
What if I am short on sleep?
A single restricted night can impair sustained attention. [7] Persistent trouble with sleep or concentration is a reason to talk with a clinician.
Are energy drinks a good study aid for teens?
The FDA reports that medical experts advise against energy drinks for children and teens. [8] Ask a pediatrician or pharmacist about any supplement.
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.
Safety and who should ask first
- Caffeine limits are individual. The FDA has cited 400 milligrams a day as an amount not generally associated with negative effects for most adults, and says sensitivity, medicines and conditions change this. [8] (FDA page current as of August 2024.) Caffeine is also in energy drinks, tablets and some formulas, so check the caffeine and L-theanine formulas page.
- Teens and young students. Medical experts, according to the FDA, advise against energy drinks for children and teens. [8] See guidance for students, teens and young adults.
- Non-prescribed stimulants. A systematic review found little evidence that academic performance improves in people without ADHD, and that adverse outcomes, including death, occur in some individuals. [9]
- Medicines and conditions. Ask a pharmacist or clinician if you take medicines, are pregnant or breastfeeding, or have a heart, anxiety, sleep or kidney or liver condition. [10] See medication interactions.
- Product quality. The systematic review above notes that people do not always know what is in a supplement. [5] See quality testing.
References
- PubMed abstract: Plant-derived nootropics and human cognition: A systematic review (Critical reviews in food science and nutrition 2023). Read 2026-10-23.
- PubMed abstract: Effects of Tea (Camellia sinensis) or its Bioactive Compounds l-Theanine or l-Theanine plus Caffeine on Cognition, Sleep, and Mood in Healthy Participants: A Systematic Review and Meta-Analysis of Randomized Controlled Trials (Nutrition reviews 2025). Read 2026-10-23.
- PubMed abstract: L-theanine and caffeine improve task switching but not intersensory attention or subjective alertness (Appetite 2010). Read 2026-10-23.
- PubMed abstract: High-dose L-theanine-caffeine combination improves neurobehavioural and neurophysiological measures of selective attention in acutely sleep-deprived young adults: a double-blind, placebo-controlled crossover study (The British journal of nutrition 2025). Read 2026-10-23.
- PubMed abstract: Dietary Supplement Ingredients for Optimizing Cognitive Performance Among Healthy Adults: A Systematic Review (Journal of alternative and complementary medicine (New York, N.Y.) 2021). Read 2026-10-23.
- PubMed abstract: Lifestyle behaviors during exam periods and their association with academic performance among Palestinian medical students: a cross-sectional study (BMC medical education 2026). Read 2026-10-23.
- PubMed abstract: Impact of one night of sleep restriction on sleepiness and cognitive function: A systematic review and meta-analysis (Sleep medicine reviews 2024). Read 2026-10-23.
- FDA: Spilling the Beans: How Much Caffeine is Too Much?. Read 2026-10-23.
- PubMed abstract: Systematic Review: Nonmedical Use of Prescription Stimulants: Risk Factors, Outcomes, and Risk Reduction Strategies (Journal of the American Academy of Child and Adolescent Psychiatry 2020). Read 2026-10-23.
- FDA 101: Dietary Supplements. 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.