GradedHealth

Does L-theanine help you sleep?

Two recent reviews of trials found the tea amino acid L-theanine gives small gains in how people rate their sleep. Device-measured results are mixed.

Published October 2026

Short answer

Only a small gain, mostly in how people rate their own sleep; device-measured results are mixed and long-term use is little studied. Evidence grade B (Moderate). Meta-analysis of 18 and systematic review of 13 mostly small RCTs; downgraded once for risk of bias (open-label trials included).

Key takeaways

  • A 2025 meta-analysis of 18 randomised trials (897 people) found small improvements in self-rated time to fall asleep, daytime problems and overall sleep quality [1].
  • In a six-week trial of 98 boys with ADHD, L-theanine at 400 mg a day improved sleep efficiency on a wrist device, but time to fall asleep did not change [2].
  • The trials cited reported no significant side effects at 400 mg a day [2], and all side effects resolved in a 28-day trial at the same dose [3].
  • Pregnancy, medicine interactions and long-term use were not covered by the studies read, so talk to a doctor first if you take medicines or are pregnant [4].

The short version

Does L-theanine help you sleep? Only a little, and mostly in how people rate their own sleep. L-theanine is an amino acid found in tea leaves [4]. Reviews of L-theanine trials found small gains in self-rated sleep [1][4], but results measured with devices are mixed [2][3].

What the studies show

  • A 2025 meta-analysis pooled 18 randomised trials with 897 people. It found small improvements in self-rated time to fall asleep, daytime problems and overall sleep quality [1].
  • A 2026 systematic review of 13 trials with 550 people reported benefits on both objective and self-reported measures. These included time to fall asleep, staying asleep, sleep satisfaction and feeling refreshed on waking [4].
  • Device results are less clear. In a six-week trial of 98 boys with ADHD taking 400 mg a day, sleep efficiency improved more than placebo, but time to fall asleep did not change [2].
  • In a 28-day trial of 30 stressed adults taking 400 mg a day, the L-theanine group had less light sleep than the placebo group on a wrist device [3].

The nuances

  • Trials used 50 to 900 mg a day, and the reviewers suggest 200 to 450 mg a day [4].
  • Some trials mixed L-theanine with other ingredients. One combined it with tryptophan, glycine, magnesium and tart cherry, so its effect cannot be separated from the others [5].
  • In one trial of 46 adults with generalised anxiety, L-theanine did not beat placebo on insomnia severity. People taking it did report more sleep satisfaction than placebo [6].
  • Many individual trials are small, with 16 to 98 people in the trials cited here [5][2][3].

What this means for you

The trials cited reported few side effects at 200 to 400 mg a day [2][3]. Pregnancy, interactions with medicines and long-term use were not covered by the studies read, so talk to a doctor before use if you take medicines, are pregnant or have a kidney or liver condition. For the full safety picture, see the L-theanine page. If sleep problems persist, see sleep for the wider evidence.

Go deeper

  • L-theanine — L-theanine, an amino acid from tea leaves, gives small gains in self-rated sleep in reviews of mostly small trials.

References

  1. The effects of L-theanine consumption on sleep outcomes: A systematic review and meta-analysis.. Sleep Med Rev, 2025.
  2. The effects of L-theanine (Suntheanine®) on objective sleep quality in boys with attention deficit hyperactivity disorder (ADHD): a randomized, double-blind, placebo-controlled clinical trial.. Altern Med Rev, 2011.
  3. Safety and Efficacy of AlphaWave® L-Theanine Supplementation for 28 Days in Healthy Adults with Moderate Stress: A Randomized, Double-Blind, Placebo-Controlled Trial.. Neurol Ther, 2024.
  4. Examining the effect of L-theanine on sleep: a systematic review of dietary supplementation trials.. Nutr Neurosci, 2026.
  5. Nutritional Modulation of Sleep Latency, Duration, and Efficiency: A Randomized, Repeated-Measures, Double-Blind Deception Study.. Med Sci Sports Exerc, 2023.
  6. L-theanine in the adjunctive treatment of generalized anxiety disorder: A double-blind, randomised, placebo-controlled trial.. J Psychiatr Res, 2019.