L-Theanine

L-theanine is an amino acid found in tea. Small studies suggest it may promote relaxation without drowsiness in some people and may help with stress or sleep quality, but trials are small and short, and it is not an anxiety treatment. If anxiety affects daily life, a clinician can help.

Adults interested in relaxation support who have no medical reason to avoid it. Whether it suits you depends on your health, medicines and test results — ask a clinician.

Studies have used roughly 100–400 mg daily. This is not a recommendation. Doses vary by product and person; this is not personal medical advice.

Some small studies measured effects within hours; others over several weeks. Effects vary.

Generally well tolerated in studies; headache, dizziness or stomach upset can occur. Long-term safety data are limited.

Ask your doctor if you take blood-pressure medicines or sedatives.

Evidence level (our editorial summary, not a formal grading): Limited.

Pregnancy & breastfeeding: Safety data in pregnancy and breastfeeding are limited; ask your provider.

Medication interactions: May add to the effect of blood-pressure medicines and sedatives.

Talk to a healthcare professional before use if you are pregnant, breastfeeding, planning pregnancy, have a medical condition, take any medicine, or are scheduled for surgery. Dietary supplements are not approved by the FDA for safety or effectiveness before they are sold, and quality varies between products.

Reliable sources to check: NIH Office of Dietary Supplements fact sheets · NCCIH Herbs at a Glance · MedlinePlus Herbs & Supplements · FDA — Dietary Supplements