L-theanine
Cognitive · Amino acid (tea-derived)
Tier B+
Bottom line
Read Off Label grades L-theanine as B+ (7.1/10) based on moderate evidence, med benefit magnitude, and a low-risk safety profile.
Combination with caffeine is the most evidence-backed nootropic stack — Camfield 2014 meta-analysis showed moderate improvements in attention switching/accuracy in first 2 hours post-dose.
Studied, labeled, or reported-use context: 100-400 mg/day; commonly 100-200 mg paired with caffeine — OTC; not individualized guidance.
If you were testing this on yourself
Two properties decide whether an n-of-1 experiment is readable and recoverable. These describe the experiment — they are not a judgment about whether to run it, and nothing here is a recommendation.
Can you undo it?
Reverses on stopping
Short half-life, no accumulation, no withdrawal. Stops when you stop.
Can you tell if it worked?
Readable — 30–60 minutes
Subjective jitteriness when taken with caffeine; subjective calm otherwise.
What would fool you The endpoint is entirely subjective and the expectancy effect for a calming supplement is large. This is one of the few things on this list where a reader could genuinely self-blind — identical capsules, someone else randomising the order — and without that, a positive result means very little.
What the evidence says
Combination with caffeine is the most evidence-backed nootropic stack — Camfield 2014 meta-analysis showed moderate improvements in attention switching/accuracy in first 2 hours post-dose. Ratio typically 2:1 theanine:caffeine. A 2026 systematic review/meta-analysis (31 RCTs, n=1,168; Molecular Psychiatry) found a single 200 mg dose significantly improved choice reaction time (SMD 0.51) as monotherapy -- the first large pooled synthesis of L-theanine alone, not just the caffeine stack. Stress reduction was modest and largely driven by high-risk-of-bias studies; no effect on fatigue; a preliminary antidepressant signal (SMD 0.69) needs confirmation in clinical populations.
Mechanism
Non-proteinogenic amino acid from tea; crosses BBB; increases alpha brain waves; mild GABA agonism; glutamate receptor modulation; calming without sedation
Studied, labeled, or reported dose & route
100-400 mg/day; commonly 100-200 mg paired with caffeine
This records doses and routes described in studies, approved labeling, clinical practice, or documented use. It is not individualized guidance and does not establish safety; context changes with indication, formulation, health history, monitoring, and other medicines.
Citations
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Common questions
- What does the evidence show about L-theanine's effects?
- Read Off Label rates the evidence for L-theanine as Moderate and the benefit magnitude as med, producing an overall grade of B+ (7.1/10). Combination with caffeine is the most evidence-backed nootropic stack — Camfield 2014 meta-analysis showed moderate improvements in attention switching/accuracy in first 2 hours post-dose.
- What safety findings are reported for L-theanine?
- L-theanine has a low risk profile in the database. Low Legal status: OTC.
- What doses or routes are reported for L-theanine?
- 100-400 mg/day; commonly 100-200 mg paired with caffeine This is context from studies, approved labeling, clinical practice, or documented use; it is not individualized guidance and does not establish safety.
- How does L-theanine work?
- Non-proteinogenic amino acid from tea; crosses BBB; increases alpha brain waves; mild GABA agonism; glutamate receptor modulation; calming without sedation
This is an independent synthesis of published research by a non-clinician. Scores are opinions supported by citations, not prescriptions. See the full disclaimer and methodology for how this score was produced and what it does and doesn't mean.