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ingestible · for anxiety & stress relief

L-Theanine

Reviewed by the Nimbera editorial team · Last updated May 2026

A randomized double-blind placebo-controlled crossover RCT (Hidese et al. 2019, n=30) found 4 weeks of 200 mg daily L-theanine significantly reduced trait anxiety scores (STAI-T), depression scores, and sleep disturbance scores compared to placebo in healthy adults.$10-$25 for a 60-120 capsule bottle.

How to use

Take 100-200 mg of L-theanine once or twice daily. For acute stress relief, a single 200 mg dose can be taken 30-60 minutes before a stressful event. For ongoing anxiety support, 200 mg daily with breakfast or lunch. Pairs synergistically with moderate caffeine (e.g. 1 cup of coffee or tea) for calm focus.

How it works

L-theanine, a non-protein amino acid found naturally in green tea, crosses the blood-brain barrier and promotes alpha brain wave activity (associated with relaxed alertness). It modulates glutamate neurotransmission and increases GABA, dopamine, and serotonin levels, reducing excitatory nervous system activity without causing sedation.

Where to buy

Jarrow Formulas L-Theanine 200 mg (Amazon, iHerb), NOW L-Theanine 200 mg (Amazon, Walmart), Pure Encapsulations L-Theanine (Amazon, health food stores).

Typical cost: $10-$25 for a 60-120 capsule bottle.

Safety notes

Generally considered very safe with minimal side effects at recommended doses. May enhance the sedating effects of blood pressure medications and sedatives - use caution. Not recommended during pregnancy or breastfeeding due to insufficient safety data. May slightly lower blood pressure - monitor if you have hypotension.

Drug & supplement interactions

  • Always tell your doctor or pharmacist about any supplements you take.
  • Interactions can occur with prescription medications, blood thinners, and immunosuppressants.
  • Herbal remedies can affect how the body absorbs or metabolises drugs.
  • Check drugs.com interactions checker before starting.

Clinical source

Hidese et al., L-theanine & stress-related symptoms: RCT in healthy adults, Nutrients, 2019

This information is compiled from primary clinical literature and is for informational purposes only. It is not a substitute for professional medical advice. Read our full disclaimer.