Amino acids & related
L-Theanine
Names you may see: theanine tea amino acid gamma glutamylethylamide
The quick take
L-theanine is an amino acid found in tea and used in relaxation and focus supplements.
A closer look
What forms will I see on a label?
Available in capsules, powders and combination formulas. Check whether caffeine or other active ingredients are also present.
Why people use it
People choose L-theanine for relaxation, managing stress and sleep quality. It also appears in focus formulas, sometimes paired with caffeine.
These are common goals and marketing uses. The evidence section below explains what research supports.
What does the evidence tell us?
Small human studies suggest potential effects on stress, sleep or attention, but findings do not establish treatment for anxiety or sleep disorders.
What should I know before using it?
Discuss use with a pharmacist if you take sedating medicines. Avoid during pregnancy or breastfeeding unless advised by a clinician. Supplement amounts differ from those obtained through ordinary tea consumption.
Sources & further reading
Memorial Sloan Kettering Cancer Center — L-theanine ↗
Content reviewed: September 30, 2026
General educational information. Follow the product label and seek individual advice when needed.