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L-Theanine

promoting relaxation and focus

Evidence · Grade DSafety · Generally safe
Meta-analysis availableSystematic review availableHuman trial evidenceTraditional useInteraction riskNeeds more research

Amino acid from green tea that promotes calm without sedation.

L-Theanine is an amino acid primarily found in green tea leaves. It is known for its potential to promote relaxation without causing drowsiness. It may influence brain wave activity, specifically increasing alpha waves, which are associated with a state of relaxed alertness. Some individuals use L-Theanine to support cognitive function, manage stress, and improve sleep quality. While it is generally considered safe, the current scientific evidence supporting its efficacy for many of its purported benefits is still developing and requires further robust research.

Quick answer

What it is: L-Theanine is an amino acid primarily found in green tea leaves.

May support:Migraine, Insomnia, Anxiety, Hypertension, Chronic Stress, Bipolar Disorder, OCD, Sleep Apnea, Anxiety Disorder, Perimenopause, Restless Leg Syndrome, High Blood Pressure, Burnout, PTSD, Brain Fog, ADHD, Panic Disorder, Adrenal Fatigue, Depression

Evidence:Evidence · Grade D

Safety:Safety · Generally safe

Evidence Summary

Evidence · Grade D

The current evidence for L-Theanine's efficacy for many conditions is limited. While some human studies exist, a lack of comprehensive, large-scale, placebo-controlled clinical trials prevents definitive conclusions. Much of the understanding comes from preliminary research and smaller studies.

Last reviewed · Jun 2026

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Commonly Combined With

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Why It Works

L-Theanine is thought to cross the blood-brain barrier and influence neurotransmitter levels, including GABA, serotonin, and dopamine, and to increase alpha brain wave activity.

How it works in more detail

L-Theanine is believed to exert its effects by crossing the blood-brain barrier. Once in the brain, it may modulate the levels of several neurotransmitters. It is thought to increase gamma-aminobutyric acid (GABA), an inhibitory neurotransmitter that promotes relaxation. Additionally, L-Theanine may influence the levels of serotonin and dopamine, which are involved in mood regulation, sleep, and cognitive function. A key proposed mechanism is its ability to increase alpha brain wave activity, which is associated with a state of relaxed alertness, often observed during meditation.

How to use

Always consult a qualified clinician.

Editorial guidance

Suggested dosage
Common consumer dosages range from 100 mg to 400 mg per day, typically taken in capsule or powder form. It is often taken once or twice daily, or as needed for relaxation or focus.
Research dosage range
Studies have explored dosages ranging from 50 mg to 400 mg, with some research using up to 600 mg per day.
Typical onset
Effects may be noticed within 30 to 60 minutes after ingestion, with peak effects potentially occurring within 1 to 2 hours.
Typical forms
capsule, powder
Quality markers
Look for products that are third-party tested for purity and potency. Ensure the product specifies 'L-Theanine' rather than 'Theanine' to confirm it is the biologically active form. Check for certifications like GMP (Good Manufacturing Practices).
Medication interactions
  • Antihypertensive drugs (may lower blood pressure further)
  • Stimulants (may counteract effects)
Avoid if
  • Pregnant or breastfeeding (due to lack of sufficient data)
  • Taking blood pressure-lowering medications (potential additive effect, consult doctor)

Community tips

No community tips yet — be the first to share what worked for you.

Suggested dosage

Common consumer dosages range from 100 mg to 400 mg per day, typically taken in capsule or powder form. It is often taken once or twice daily, or as needed for relaxation or focus.

General guidance — discuss specifics with a clinician.

Active medicinal compounds

L-Theanine (gamma-glutamylethylamide)

Traditional use

L-Theanine is a component of green tea, which has been consumed for centuries in East Asian cultures for its calming and focusing properties. Traditional use is primarily through the consumption of tea rather than isolated supplements.

Safety

Safety warnings

L-Theanine is generally considered safe for most adults when consumed in typical amounts found in food or supplements. However, pregnant or breastfeeding individuals, or those with underlying medical conditions, should consult a healthcare professional before use. There is limited long-term safety data.

Avoid if

  • Pregnant or breastfeeding (due to lack of sufficient data)
  • Taking blood pressure-lowering medications (potential additive effect, consult doctor)

Medication interactions

  • Antihypertensive drugs (may lower blood pressure further)
  • Stimulants (may counteract effects)

Reported side effects

  • Generally well-tolerated
  • Mild gastrointestinal upset (rare)

General guidance — discuss specifics with a clinician.

Evidence ecosystem

Scientific literature, clinical guidance, government sources, ongoing research, traditional use, and lived experience — grouped by source type and quality.

Overall grade (D)

The current evidence for L-Theanine's efficacy for many conditions is limited. While some human studies exist, a lack of comprehensive, large-scale, placebo-controlled clinical trials prevents definitive conclusions. Much of the understanding comes from preliminary research and smaller studies.

Filter by source type

Meta-Analyses(1)

Pooled analyses across multiple human trials.

Very High Quality

  • Medicinal herbs for the treatment of anxiety: A systematic review and network meta-analysis.

    Zhang W, Yan Y, Wu Y, Yang H, Zhu P, Yan F · Pharmacological research · 2022

    Anxiety disorder is a common psychiatric illness. Medicinal herbs have become a field of interest in the treatment of anxiety. This study aimed to evaluate and compare the efficacy and acceptability of all possible medicinal herbs for the treatment of anxiety. A Bayesian network meta-analysis was conducted for adults with diagnosed or subthreshold anxiety in randomized controlled trials identified in PubMed, EMBASE, the Cochrane Library, and Web of Science, searched between Jan 1, 1987, and Dec 31, 2021. The outcomes included efficacy (measured by endpoint Hamilton Anxiety Scale [HAMA] Scores) and acceptability (discontinuation by ineffectiveness, worsening of the symptoms, or adverse events). A total of 29 trials were reviewed, comparing 12 medicinal herbs. Silexan (mean difference [MD]: -3.84, 95% credible interval [CrI]: -6.31 to -1.34) displayed a significant effect on anxiety, and possibly benefitted the treatment of depression (standard mean difference [SMD]: -0.37, 95% confide

    Meta-AnalysisPubMedVery High Quality

Systematic Reviews(1)

Structured reviews of the full body of evidence (incl. Cochrane).

Very High Quality

  • The effects of L-theanine supplementation on the outcomes of patients with mental disorders: a systematic review.

    Moshfeghinia R, Sanaei E, Mostafavi S, Assadian K, Sanaei A, Ayano G · BMC psychiatry · 2024

    When utilized as an adjunct with antidepressants, antipsychotics, and other psychopharmacological drugs, certain amino acids, such as L-Theanine (LT), have shown potential effectiveness in enhancing the symptomatic outcomes of patients with mental disorders. Despite this, there is a lack of previous systematic reviews examining these associations. Therefore, we conducted a systematic review of randomized controlled trials examining these relationships. A comprehensive systematic review was conducted, scouring six electronic databases (PubMed, Scopus, PsycINFO, Web of Science, CINAHL Complete, and Cochrane) from their inception up to June 2023, specifically focusing on randomized controlled trials that investigated the effects of LT supplementation on the outcomes of patients with mental health disorders. The Cochrane Risk of Bias Tool for Randomized Trials was employed to assess the quality of the included studies. Among the 419 publications identified, 11 studies from six countries

    Systematic ReviewPubMedVery High Quality

Randomized Human Trials(1)

Controlled human studies with random assignment.

High Quality

  • Effect of a Combination of Magnesium, B Vitamins, Rhodiola, and Green Tea (L-Theanine) on Chronically Stressed Healthy Individuals-A Randomized, Placebo-Controlled Study.

    Noah L, Morel V, Bertin C, Pouteau E, Macian N, Dualé C · Nutrients · 2022 · n=49

    The effect of a combination of magnesium, vitamins B6, B9, B12, rhodiola and green tea/L-theanine (Mg-Teadiola) on stress was evaluated in chronically stressed, otherwise healthy individuals. Effects on stress-related quality-of-life parameters (sleep and perception of pain) were also explored. Adults with stress for ≥1 month, scoring ≥14 points on the Depression Anxiety Stress Scale (DASS)-42 questionnaire, were randomized (1:1) to receive oral Mg-Teadiola (n = 49) or a placebo (n = 51), for 28 days, with a follow-up assessment on Day 56 (NCT04391452). The primary endpoint was the change in the DASS-42 stress score from baseline to Day 28 with Mg-Teadiola versus placebo. The DASS-42 stress scores significantly decreased from baseline to Day 28 with Mg-Teadiola versus placebo (effect size, 0.29; 95% CI [0.01, 0.57]; p = 0.04). Similar reductions were observed on Day 14 (p = 0.006) and Day 56 (p = 0.02). A significant reduction in sensitivity to cold pain (p = 0.01) and a

    Randomized TrialPubMedHigh Quality

Observational Studies(1)

Cohort, case-control, and cross-sectional human studies.

Moderate Quality

  • Sexual Performance Anxiety.

    Pyke RE · Sexual medicine reviews · 2020

    Sexual performance anxiety (SPA) is one of the most prevalent sexual complaints; yet, no diagnosis is recognized for either gender. Thus, research into treatment has been minimal. Review the prevalence of SPA and its relation to sexual dysfunctions and anxiety disorders. Compare SPA to (non-sexual) performance anxiety and social anxiety (PA/SA). Apply pharmacologic principles to the known properties of drugs and phytotherapies to hypothesize treatments for SPA. Review SPA and PA/SA through PubMed searches for relevant literature from 2000 to 2018. Prevalence was estimated using population-representative surveys. For treatment results, controlled clinical trial results were prioritized over open-label trial results. SPA affects 9-25% of men and contributes to premature ejaculation and psychogenic erectile dysfunction (ED). SPA affects 6-16% of women and severely inhibits sexual desire. Cognitive behavior therapy and mindfulness meditation training have been proven effective for

    Observational StudyPubMedLow Quality

Evidence Summaries(1)

Curated cross-source summaries (TRIP Database and similar).

High Quality

  • L-Theanine

    Natural Medicines Database

    The Natural Medicines Database offers a comprehensive professional monograph on L-Theanine, detailing its uses, effectiveness, mechanism of action, and safety. This resource provides an evidence-based rating for various conditions, including potential relevance to neurological functions, but may not have specific migraine recommendations.

    Evidence SummaryNatural Medicines DatabaseHigh Quality

Limitations: A significant limitation is the absence of a robust body of high-quality, large-scale randomized controlled trials. Many existing studies are small, have short durations, or may lack sufficient methodological rigor. This makes it challenging to draw strong conclusions about its effectiveness and optimal use.

This page is educational. Statements use phrases like "may support" and "has been studied for"because no remedy here is approved to cure, treat, or reverse any condition. Discussion happens on the ailment pages — community statistics here are derived from those reports. Always consult a qualified clinician.

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