What it’s for
- Studied for relaxation and sleep
An amino acid found in tea and sold separately, sometimes alongside caffeine.
Purpose, evidence and practical considerations.
The cited anxiety trial did not establish an advantage over placebo for anxiety symptoms. Some sleep-related findings were exploratory; effects depend on the outcome and formulation studied.
Confidence: weak
Short studies generally report good tolerance, but long-term and pregnancy data are limited. It may cause drowsiness or lower blood pressure and can add to sedatives or antihypertensive medicines.
L-theanine is a tea amino acid with low-affinity glutamate-system effects and small human signals for altered alpha-band activity and stress responses. These mechanisms do not establish treatment of anxiety or insomnia.
Regulatory status: dietary supplement ingredient; not an FDA-approved anxiety or insomnia treatment
The evidence on this page does not automatically apply to:
How people use it, with their schedules, context and original sources.
100–400 mg · 30–60 min before bed
L-theanine is listed as an ingredient or component in these reviewed interventions.
Blueprint
Open interventionThese share a protocol with this intervention. This does not establish that they work together or are suitable alternatives.