Scientists reviewed 13 studies involving 550 people to see if L-theanine, a natural compound found in tea leaves, can improve sleep. They found that taking 200-450 mg of L-theanine daily appears to help people fall asleep faster, sleep more soundly, and wake up feeling more refreshed. Unlike sleeping pills, L-theanine doesn’t make you drowsy during the day or hurt your thinking ability. This natural supplement seems to work by helping your body relax without causing sedation, making it a promising option for adults struggling with sleep issues.

The Quick Take

  • What they studied: Whether L-theanine, a natural compound from tea leaves, can help adults sleep better
  • Who participated: 550 adults across 13 different sleep studies, including both healthy people and those with sleep troubles
  • Key finding: Taking 200-450 mg of L-theanine daily appears to help people fall asleep faster, stay asleep longer, and feel more rested when they wake up
  • What it means for you: If you have trouble sleeping, L-theanine might be a natural alternative to try, but talk to your doctor first, especially if you take other medications

The Research Details

This was a systematic review, which means researchers gathered and analyzed all the best available studies on L-theanine and sleep. They searched major medical databases from the beginning of recorded research until February 2025, looking for high-quality trials. Three independent researchers reviewed each study to make sure only the most reliable research was included. They found 13 studies that met their strict criteria - 11 were randomized controlled trials (the gold standard of research) and 2 were open-label trials where participants knew they were taking L-theanine.

Systematic reviews are considered some of the strongest evidence in science because they combine results from multiple studies, giving us a bigger picture than any single study could provide. By pooling data from 550 people across different studies, researchers can be more confident about whether L-theanine really works for sleep.

The fact that most studies were randomized controlled trials is important because it means participants were randomly assigned to get either L-theanine or a placebo, reducing bias. However, the total number of participants (550) is relatively small for a systematic review, and more research is still needed.

What the Results Show

The review found that L-theanine supplementation consistently improved multiple aspects of sleep. People taking L-theanine fell asleep faster (reduced sleep latency), stayed asleep better throughout the night (improved sleep maintenance), and had better overall sleep efficiency - meaning they spent more of their time in bed actually sleeping rather than lying awake. The effective dose range was 200-450 mg per day, with studies testing anywhere from 50-900 mg daily. Importantly, these benefits were seen in both objective measurements (like sleep monitoring devices) and in how people reported feeling about their sleep quality.

Beyond just sleeping better, people taking L-theanine reported feeling more satisfied with their sleep and waking up feeling more refreshed and recovered. Unlike traditional sleep medications, L-theanine didn’t cause daytime drowsiness or negatively affect thinking and memory. The supplement appeared to work by promoting relaxation without sedation, which may explain why people felt alert during the day despite sleeping better at night.

These findings build on earlier research showing L-theanine’s calming effects and recent laboratory studies suggesting it might help with sleep. This systematic review provides the strongest human evidence to date that L-theanine can indeed improve sleep, confirming what smaller individual studies had suggested.

The review included a relatively small total number of participants, and most studies were short-term, so we don’t know about long-term effects. More research is needed in people with diagnosed insomnia, as most studies included generally healthy adults with mild sleep issues. The studies also used different ways to measure sleep, making it harder to compare results directly.

The Bottom Line

Based on current evidence, adults with sleep difficulties might consider trying 200-450 mg of L-theanine daily, but should consult with a healthcare provider first. Start with the lower end of this range and see how you respond before increasing the dose.

Adults experiencing difficulty falling asleep, staying asleep, or waking up unrefreshed may benefit most. People looking for natural alternatives to prescription sleep aids should find this particularly relevant. However, those with severe insomnia or other sleep disorders should work with a doctor rather than self-treating.

While the studies don’t specify exactly when benefits appear, sleep supplements typically show effects within days to weeks of consistent use. Individual responses may vary, so give it at least 2-4 weeks of consistent use before deciding if it’s working for you.

Want to Apply This Research?

  • Track your sleep latency (time to fall asleep), number of nighttime awakenings, and morning refreshment rating on a 1-10 scale before and after starting L-theanine
  • Set a consistent L-theanine supplementation schedule 30-60 minutes before bedtime and log it alongside your sleep quality metrics in the app
  • Monitor sleep patterns for 2 weeks before starting L-theanine to establish baseline, then track for 4-6 weeks after starting to assess effectiveness and optimal timing

This information is for educational purposes only and should not replace professional medical advice. Consult with a healthcare provider before starting any new supplement, especially if you have sleep disorders, take medications, or have underlying health conditions.