Amino Acid
L-Theanine
Also known as: Theanine
Calming amino acid from tea that promotes relaxation without sedation. Synergistic with caffeine for focused calm.
Last reviewed June 2026 · Evidence graded from peer-reviewed research, not editorial opinion. Educational only — not medical advice.
Every L-Theanine product we have scored
| # | Product | Score | Per serving |
|---|---|---|---|
| 1 | Nutricost Caffeine + L-Theanine Capsules | 97 A | $0.53 |
| 2 | Nootropics Depot L-Theanine Capsules | 95 A | $0.18 |
| 3 | Double Wood L-Theanine Supplement | 95 A | $0.17 |
| 4 | Momentous L-Theanine | 95 A | $0.67 |
| 5 | Nutricost L-Theanine Capsules | 95 A | $0.08 |
| 6 | BulkSupplements L-Theanine Powder | 94 A | $0.06 |
| 7 | NOW Foods L-Theanine Pure Powder | 94 A | $0.24 |
| 8 | Transparent Labs Fat Burner | 92 A | $0.92 |
| 9 | Life Extension Enhanced Stress Relief | 91 A | $0.70 |
| 10 | NOW Foods L-Theanine | 91 A | $0.16 |
| 11 | Thorne Theanine | 90 A | $0.76 |
| 12 | Transparent Labs BULK Pre-Workout | 90 A | $1.67 |
Scored on dose accuracy, form, label transparency and third-party testing. Per-serving cost is list price divided by servings per container. No brand pays to be listed or ranked.
Common questions
How much L-Theanine should I take?
The typical range is 100-400 mg daily. Safe long-term
When should I take L-Theanine?
Any time; with caffeine for focus. Optional.
Which form of L-Theanine is best?
Capsules — Suntheanine common. Other forms in the catalog: Powder, Tea.
Is L-Theanine safe?
Commonly reported: Very well tolerated. Serious warnings: None. Safe
Which L-Theanine supplement scores highest?
Nutricost Caffeine + L-Theanine Capsules, at 97/100. Scored on dose accuracy, form, label transparency and third-party testing — no brand pays to be listed or ranked.
Daily target & upper limit
200 mg / dayL-Theanine has an established daily reference intake. See best forms, label synonyms, upper-limit warnings, and top-scoring supplements:
L-Theanine dosage reference →Primary uses
- Relaxation
- Focus
- Sleep support
- Anxiety relief
What systematic reviews concluded
Outcomes that systematic reviews of L-Theanine reached a verdict on: 1 with a benefit, 2 unclear. Each is quoted from a review and linked to it on PubMed. How these were read.
Reviews found a benefit (1)
“L-theanine was shown to significantly improve subjective sleep onset latency (SMD = 0.15, 95 % CI [0.01, 0.29], p = 0.04; n = 10 studies), subjective daytime dysfunction (SMD = 0.33, 95 % CI [0.16, 0.49], p < 0.001; n = 9 studies), and overall subjective sleep quality score (SMD = 0.43, 95 % CI [0.04, 0.83], p = 0.03; n = 12 studies).” PMID 40056718 · 2 reviews
Not enough to say: adhd symptoms; stress and anxiety.
1 finding from reviews in specific patient groups (such as cancer, pregnancy or surgery) is not shown here.
How it works
- Increases alpha brain waves
- Modulates GABA, dopamine, serotonin
- Crosses blood-brain barrier
Dosage
- Typical range
- 100-400 mg daily
- Timing
- Any time; with caffeine for focus
- With food
- Optional
- Duration
- Safe long-term
- Special populations
- Anxious, need calm focus
Forms
- Capsules
- Powder
- Tea
Safety
Common side effects
- Very well tolerated
Contraindications
- None
Products containing L-Theanine
Top-scoring supplements in our catalog that list L-Theanine on the label. Each product is graded on Formulate's ingredient-level rubric — dose accuracy, form, transparency, and third-party testing.
Known interactions
Evidence notes
Well-studied for calm focus
Grade A: Multiple well-designed human trials support the main claims.
Cited research for L-Theanine
Clinical studies referenced across Formulate guides that mention l-theanine. Each links to the full study page with PubMed source + the guides that cite it.
- Hidese S, Ogawa S, Ota M, et al. (2017)Acta Neuropsychiatrica
Effects of chronic l-theanine administration in patients with major depressive disorder: an open-label study
- Nobre AC, Rao A, Owen GN (2008)Asia Pacific Journal of Clinical Nutrition
L-theanine, a natural constituent in tea, and its effect on mental state
L-Theanine compared head-to-head
Related in Amino Acid
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Medical disclaimer. This page is educational and does not replace advice from a qualified healthcare provider. Individual needs and risks vary — consult a professional before starting, stopping, or combining supplements, especially if you are pregnant or nursing, taking medication, or managing a health condition.