Amino acid

L-Theanine

Last reviewed September 28, 20260 sources
In short

L-theanine is an amino acid found naturally in tea leaves. It’s sold alone or combined with caffeine or magnesium. SuppScout’s evidence review for L-theanine is in progress.

Research in progress. This ingredient page doesn’t yet meet SuppScout’s bar for a complete reference (sourced evidence summary, considerations and sufficient detail), so search engines are asked not to index it. The information shown is sourced where cited.

Quick facts

Found in
Tea (Camellia sinensis)

Common l-theanine supplement forms

  • L-theanine (free form)
  • Branded fermentation-derived L-theanine

Detailed form pages for L-Theanine are being researched.

Food sources

  • Green and black tea

Potential considerations

  • Evidence summary not yet published — check back as this page is researched.

Products containing l-theanine

No products listed yet

SuppScout hasn’t added l-theanine products yet.

Shopping for L-Theanine?

Before you buy, check the label for the form and amount per serving, look for a USP, NSF or Informed Choice seal, and compare cost per serving rather than bottle price.

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This page is educational and is not medical advice. Talk to a healthcare professional before starting a supplement, especially if you have a medical condition, take medications, or are pregnant or breastfeeding. Medical disclaimer.