Doctor's Best · L-theanine · Capsules
Is Doctor's Best L-Theanine 150 mg underdosed?
1 serving = 1 capsuleDirections: 1 serving a dayLabel as of 16 Jun 2022 · NIH DSLD
Verdict
150 mg per servingone dose · studies use 100–200 mg of l-theanine
Effective doseOne serving contains 150 mg; studies use 100–200 mg in one dose before training. The label's directions allow 1 serving a day.
One capsule gives 150 mg, enough on its own for the low end of what studies use (100 mg); it ranks 12th of 13 L-theanine supplements here by dose.
What the label says
- L-Theanine per serving
- 150 mg in 1 capsule
- Servings a day
- 1 serving a day
- L-Theanine a day, as directed
- 150 mg
- Research dose
- 100–200 mg Evidence: Weak
Suggested Adult Use: Take 1 capsule daily without food, or as recommended by a nutritionally informed physician.
More about l-theanine: forms, timing and the studies behind the dose.
Same category, compared
All 13 L-theanine supplements we checked, ranked by dose (commission never changes the order). Studies use 100–200 mg of l-theanine; servings counted to 100 mg.
| Product | Per serving | Servings to reach it | Form |
|---|---|---|---|
| Double Wood L-Theanine 200 mg | 200 mg | 1 or less | Capsules |
| Jarrow Formulas Theanine 200 mg | 200 mg | 1 or less | Capsules |
| Momentous L-Theanine | 200 mg | 1 or less | Capsules |
| Nature Made L-Theanine 200 mg Chewable | 200 mg | 1 or less | Chews |
| Nootropics Depot L-Theanine 200 mg Capsules | 200 mg | 1 or less | Capsules |
| NOW L-Theanine 200 mg | 200 mg | 1 or less | Capsules |
| NutraBio L-Theanine | 200 mg | 1 or less | Capsules |
| Nutricost L-Theanine 200 mg | 200 mg | 1 or less | Capsules |
| Pure Encapsulations L-Theanine | 400 mg | 1 or less | Capsules |
| Sports Research L-Theanine 200 mg | 200 mg | 1 or less | Capsules |
| Thorne Theanine | 200 mg | 1 or less | Capsules |
| Doctor's Best L-Theanine 150 mg (this product) | 150 mg | 1 or less | Capsules |
| Swanson Suntheanine L-Theanine 100 mg | 100 mg | 1 or less | Capsules |
Where the reference doses come from
- L-Theanine, 100–200 mg: Owen et al., 2008; Payne et al., 2025.
- Label data: National Institutes of Health, Office of Dietary Supplements. Dietary Supplement Label Database, 2026. https://dsld.od.nih.gov/. Label 269486, including its servings a day.
For a supplement taken as one dose we judge one serving, and show the most the label allows in a day. Read the full methodology or the corrections log.