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No. 021supplement
L-theanine
L-theanine is a supplement that is sold over the counter.
Also known as Theanine, Suntheanine
L-theanine is found naturally in green and black tea. People take it for a calm, focused feeling, often with caffeine, and sometimes for sleep and stress.
In 1 example journal
Is L-theanine FDA-approved?
Sold without a prescription. Supplements are not reviewed by the FDA before sale, so third-party testing matters. Sold as a dietary supplement.
As of September 23, 2026.
Key takeaways
- L-theanine is an amino acid found in tea. It is sold as a supplement for calm focus and sleep.
- A 2026 review of 31 studies found it safe, with a short-term boost to attention and a modest drop in stress.
- Sleep studies suggest people fall asleep more easily, based mostly on self-reports.
- FDA has raised no questions about its use as a food ingredient.
How does L-theanine work?
L-theanine is an amino acid that tea plants make but your body does not use to build protein. It crosses into the brain, where it is thought to have a calming effect without sedation.
It is often paired with caffeine, as in tea, where it may smooth out the jittery edge. How it works in detail is still being studied.
What does the evidence say about L-theanine?
Emerging evidenceSmall randomized trials suggest modest effects on stress and some attention measures; results are inconsistent.
What do clinicians say about L-theanine?
L-theanine looks safe, with modest short-term effects on attention and stress. Evidence for cognition is inconsistent.
A 2026 systematic review of 31 studies in Molecular Psychiatry found L-theanine safe, with a robust short-term benefit on attention and a modest reduction in stress or anxiety.
L-theanine on attention, stress and anxiety: systematic review (Mol Psychiatry 2026)A 2025 meta-analysis of 19 studies found improvements in self-reported sleep onset, sleep quality and daytime functioning.
L-theanine and sleep: meta-analysis (Sleep Med Rev 2025)A 2025 review of cognitive studies found the results inconsistent and called for standardized trials.
L-theanine and cognition: systematic review (J Clin Med 2025)FDA's GRAS inventory lists several L-theanine notices to which FDA had no questions.
FDA GRAS notice inventory: L-theanine
Summaries of published guidelines, drug labels, regulators and reviews, each attributed to its source. DiscoverMedica does not employ clinicians.
Is L-theanine right for you, and who should avoid it?
Often considered for
- Adults looking for mild calm or focus support
- Coffee drinkers who want less jitteriness
Not a fit, or needs extra care
- People on blood pressure medication or sedatives should check first
- Pregnancy or breastfeeding: not well studied
Only a licensed clinician who knows your history can decide whether it is right for you.
What are the risks and side effects of L-theanine?
- Generally well tolerated in studies.
- May add to the effect of blood pressure medications or sedatives.
- Not well studied in pregnancy or breastfeeding.
What should you ask a clinician about L-theanine?
- Could it interact with my blood pressure or anxiety medications?
- Is it reasonable to combine it with caffeine for me?
These save with the compound when you add it to My Journal, so they’re on the printout for your visit.
How do people buy L-theanine?
No prescription is needed. Supplement brands and retailers sell it online and in stores.
Check with a clinician or pharmacist first if you take prescription medication or have a chronic condition.
Choose a product with independent testing, such as NSF Certified for Sport or USP Verified, because FDA does not check supplements before they are sold.
Where some people buy it
- ThorneSells theanine capsules direct.
- MomentousSells L-theanine direct and says every product is third-party certified.
- iHerbCarries L-theanine from many brands.
From each provider’s own site, checked September 23, 2026. Programs change, so confirm the details before you sign up.
Where can I get L-theanine?
12 providers list L-theanine on DiscoverMedica, lowest listed price first.
$18.00listed price†
Buy at Life Extension $65.50listed price†
Buy at Pure Encapsulations † Prices as listed by the provider when we checked; they change.
Compare and learn
L-theanine: questions, answered
Does L-theanine help anxiety?
It may modestly reduce stress in the short term. It is not a treatment for anxiety disorders.
Can I take it with coffee?
Many people do, and studies often combine the two. Check with a clinician if you have heart or blood pressure issues.
Will it make me sleepy?
It is not a sedative. Sleep studies mostly show people report falling asleep more easily.
Can I get it through telehealth?
It does not need a prescription. You buy it from supplement brands and retailers.
Important safety information
Key risks
- Generally well tolerated in studies.
- May add to the effect of blood pressure medications or sedatives.
- Not well studied in pregnancy or breastfeeding.
Talk to a clinician first, or avoid it, if
- People on blood pressure medication or sedatives should check first
- Pregnancy or breastfeeding: not well studied
This is not a complete list of risks. Talk to a licensed clinician or pharmacist about your own situation. If you have a severe reaction, call 911. You can report side effects to the FDA through MedWatch at 1-800-FDA-1088.
Sources
- L-theanine on stress-related symptoms and cognition in healthy adults: RCT (2019)
- PubChem: L-theanine (CID 439378)
Also checked for this guide
- L-theanine on attention, stress and anxiety: systematic review (Mol Psychiatry 2026)
- L-theanine and sleep: meta-analysis (Sleep Med Rev 2025)
- L-theanine and cognition: systematic review (J Clin Med 2025)
- FDA GRAS notice inventory: L-theanine
- Momentous: Home and testing
- Thorne: Home and testing
Guide reviewed September 23, 2026.
Educational information only, not medical advice. It does not replace a conversation with a licensed clinician.
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