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SupplementScience

L-Theanine Side Effects & Safety

This content is for informational purposes only and does not constitute medical advice. Consult your healthcare provider before starting any supplement. Full disclaimer

Safety Profile

Overall safety rating: Generally Safe

Potential Side Effects

  • Exceptionally well-tolerated — one of the safest supplements available
  • Rare: mild headache
  • Rare: dizziness at very high doses
  • No known dependency, tolerance, or withdrawal effects
  • Does not impair cognitive function or cause sedation at normal doses

Drug & Supplement Interactions

  • Blood pressure medications — L-Theanine may mildly lower blood pressure
  • Stimulants — L-Theanine modulates (smooths) stimulant effects without blocking them
  • Sedatives — potential additive relaxation effects, though L-Theanine itself is not sedating

Maximum Dose

Do not exceed: 400mg/day (generally well-tolerated even at higher doses, but limited data beyond 400mg)

Full L-Theanine Guide

References

  1. (). The combined effects of L-theanine and caffeine on cognitive performance and mood. Nutritional Neuroscience. DOI
  2. (). L-theanine, a natural constituent in tea, and its effect on mental state. Asia Pacific Journal of Clinical Nutrition.
  3. (). Effects of L-theanine administration on stress-related symptoms and cognitive functions in healthy adults: a randomized controlled trial. Nutrients. DOI