Theanine

amino acidTheanine glucoside

Best before bed

What is it

L-theanine is a non-protein amino acid found naturally in tea leaves (particularly green tea) and certain mushrooms. It is widely used in supplements for its calming effect without sedation.

How it works

L-theanine crosses the blood-brain barrier and modulates several neurotransmitter systems. It increases alpha brain wave activity — the pattern associated with relaxed alertness — and influences GABA, dopamine, and serotonin levels. It also raises BDNF (brain-derived neurotrophic factor) in some animal studies. The most reliable subjective effect in humans is a calm, focused mental state without drowsiness. This is why it is commonly combined with caffeine: the caffeine provides alertness and the theanine smooths out the jittery edge. The amino acid is rapidly absorbed in the small intestine, reaching peak blood levels within 30 to 60 minutes.

Evidence for 5 uses

AI-assisted evidence assessment — talk to your doctor before relying on any single supplement.

Stress and anxiety reduction

Grade B

Good evidence

200 to 400 mg per day reduces stress and anxiety markers in several trials, particularly in people with elevated baseline stress. Effects are gentler than prescription anti-anxiety medications.

Attention and focus (with caffeine)

Grade B

Good evidence

The combination of L-theanine and caffeine (typically 100 to 200 mg of each) improves attention and reaction time more than caffeine alone, with less jitteriness.

Sleep quality

Grade C

Moderate evidence

Some trials show improved sleep quality (not necessarily duration) with 200 to 400 mg before bed. Effect is modest.

Cognitive performance

Grade C

Moderate evidence

Acute doses may modestly improve cognitive performance in stressed or fatigued individuals. Long-term cognitive benefits are unproven.

Blood pressure reduction

Grade C

Moderate evidence

May modestly reduce blood pressure in stressed individuals. Effect is small.

2 commercial forms

L-theanine (Suntheanine)

patented form used in most clinical studies

A specific branded L-theanine produced by Taiyo Kagaku. Used in most clinical research.

Generic L-theanine

comparable in most uses

Generic L-theanine produced by various manufacturers. Usually comparable to branded forms; check for third-party purity testing.

Dosage

Typical doses range from 100 to 400 mg per day. For acute calming or focus support, 200 mg is the most commonly studied single dose. A standard cup of green tea provides about 25 to 60 mg. No tolerable upper limit is established; doses up to 900 mg have been used short-term in trials.

When and how to take it

L-theanine is often taken in the evening for relaxation and sleep support, particularly because it produces a calm state without sedation. It can also be taken in the morning paired with caffeine (around 100 to 200 mg of each) for smooth focused energy. Effects begin within 30 to 60 minutes. For acute anxiety or stress, 200 mg taken as needed is a common approach. For ongoing daily use, 100 to 200 mg in the evening or split morning and evening works well.

Food sources

Food	Amount	%DV
Green tea (brewed), 1 cup	25-60 mg	—
Black tea (brewed), 1 cup	15-25 mg	—
White tea (brewed), 1 cup	30-50 mg	—
Matcha tea, 1 g powder	10-20 mg	—
Bay bolete mushrooms	trace amounts	—

Safety

L-theanine is well tolerated with few reported side effects. Some users report mild headache or drowsiness at high doses. It does not cause sedation in the way that anti-anxiety medications do. It is generally recognized as safe (GRAS) by the FDA for use in foods. Long-term safety at high supplemental doses has not been formally studied, but the long history of human green tea consumption suggests it is well tolerated.

Who should be cautious

People taking medications for blood pressure should monitor levels when starting theanine, as it may have additive blood-pressure-lowering effects. Pregnant and breastfeeding women lack safety data and should consult their doctor. Otherwise, theanine has a very benign profile.

Interactions

May enhance the effects of blood-pressure-lowering medications, slightly lowering blood pressure. Theoretical interactions with stimulants and sedatives (it modulates rather than directly stimulates or sedates). Combination with caffeine is common and well tolerated.

Frequently asked questions

Does L-theanine make you sleepy?⌄

Not in a sedating way. It promotes calm relaxation without drowsiness. Many people find it improves sleep quality without grogginess the next day.

Should I take L-theanine with caffeine?⌄

Yes, this combination is well studied. 100 to 200 mg of each provides focused energy with less jitteriness than caffeine alone.

How much L-theanine should I take?⌄

200 mg is the most commonly studied dose. For ongoing use, 100 to 400 mg per day is typical.

Can I take L-theanine every day?⌄

Yes. It is well tolerated and there is no evidence of tolerance or dependence.

Is L-theanine the same as green tea extract?⌄

No. Green tea extract contains catechins (especially EGCG), caffeine, and small amounts of L-theanine. Standalone L-theanine supplements contain higher doses without the other components.

Track Theanine with Pilora

Set up dose reminders, check interactions, and join the community in the Pilora iPhone app.

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Disclaimer: These statements have not been evaluated by the FDA. This page is educational, not a substitute for personalized medical advice. Evidence grades are AI-assisted assessments — talk to your doctor before starting any new supplement, especially if you're pregnant, breastfeeding, on medications, or managing a chronic condition.