What is it used for?
Helps (to) temporarily promote relaxation [Source note 2].
Who does this guide cover?
Adults 18 years and older
How is it taken?
Oral
Which forms are covered?
this reference excludes foods or food-like dosage forms as indicated in the Compendium of references Guidance Document.
Quantities
200 - 250 milligrams of L-Theanine, per day [Source note 3].
How is it used?
The reference does not require an additional label statement in this section. This does not establish an absence of risk.
How long is it used?
The reference does not require an additional label statement in this section. This does not establish an absence of risk.
Warnings and precautions
The reference does not require an additional label statement in this section. This does not establish an absence of risk.
When should it be avoided?
The reference does not require an additional label statement in this section. This does not establish an absence of risk.
Possible side effects
The reference does not require an additional label statement in this section. This does not establish an absence of risk.
Storage
Must be established in accordance with the requirements described in the applicable product regulations.
Preparation details
Ingredient identity, preparation requirements, and other details that define the scope of this guide.
Ingredients and preparations
| Proper name(s) | Common name(s) | Source information / Source ingredient(s) | Source information / Source material(s) | Source information / Part(s) | Source information / Preparation(s) |
|---|---|---|---|---|---|
| L-Theanine | N/A | Camellia sinensis | Leaf | Isolate |
| L-Theanine | L-Theanine | N/A | N/A | Synthetic |
References: Proper names: RSC 2205; NIH 2024; Common name: NIH 2024; Source information: RSC 2025; Zajac et al. 2003; Gennaro 2000.
Other ingredients
Must be chosen from the current source ingredient database and must meet the limitations outlined in the database.
Preparation and quality requirements
The finished product specifications must be established in accordance with the requirements described in the source authority source’s product quality guidance.
The active ingredient must comply with the requirements outlined in the source ingredient database.
The assay must demonstrate that the percentage purity of the active ingredient is no less than 98% L-theanine.
The Finished Products Specifications must include testing for chemical identity and assay/purity of the active ingredient L-theanine at the raw material or finished product stage using an appropriate enantiomerically selective separation method (i.e. HPLC/APCI-MS, RP-HPLC, etc.).
If testing is conducted at the raw material stage, data to demonstrate that the ingredient does not undergo racemization must be provided.
Guide change history
Updates to this SupplementSafety.org guide.
Minor updates
Updated guide wording, organization, and source presentation. Added our editorial change history.
Initial release
Initial SupplementSafety.org guide prepared from source reference material.
Validation: Not yet completed. Editorial updates do not constitute clinical validation.
Sources
Source information
This guide organizes source material about uses, preparations, amounts, and precautions. Read the conditions alongside each statement; the information may apply only to particular preparations or populations.
The source document includes supporting references. We have not independently summarized or assessed every cited study for this guide.
- Source document version
- January 30, 2026
- Source captured
- Aug 15, 2026
- Editorial work
- Editorial preparation. Independent clinical review has not been recorded for this guide.
Full citations are available through the link above. Verification is required to open them; reading this guide does not require verification.
Taking a medication too?
Explore our supplement–medication interaction checker. Its coverage and review status are shown with the results; a missing finding does not establish that a combination is safe.