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Interest in l-theanine for sleep has grown as people look for gentler ways to unwind at night. L-theanine is an amino acid found in green and black tea and in L-theanine supplements. It has been studied for potential effects on relaxation and sleep quality, though findings vary across studies and individuals.
Some healthy adults include L-theanine in their bedtime routines. While some report feeling calmer or finding it easier to fall asleep, these observations are personal and may not reflect broader outcomes.
L-theanine occurs naturally in tea leaves, including green and black tea, and contributes to tea’s mild umami flavor. It is also available as a dietary supplement.
The amount of L-theanine in brewed tea can vary. Supplement products provide a labeled amount, but labeling does not guarantee any specific result related to sleep quality. Some multi-ingredient sleep-support formulas include l-theanine; in these cases, it is difficult to separate any perceived effect of l-theanine from that of other ingredients.
Researchers have explored how L-theanine interacts with the central nervous system and certain brain chemicals associated with calmness and alertness. Findings differ depending on study design, dose, and participant group.
Some small studies have observed increases in alpha brain waves and changes in neurotransmitter activity after L-theanine intake. These results describe how L-theanine may influence brain wave activity in study conditions, but they do not establish a guaranteed impact on sleep quality for the general population.
Limited trials have measured biological and self-reported markers related to stress, including cortisol, with mixed results. Any reference to managing stress or promoting calm should be understood as study-specific, not as proof of a general outcome. Early research exploring L-theanine in people with attention deficit hyperactivity disorder is preliminary and not conclusive.
Some controlled trials and one systematic review have noted associations between L-theanine use and changes in self-reported sleep parameters such as sleep latency or sleep duration. These findings are limited to specific study groups and should not be viewed as evidence that l-theanine will affect everyone in the same way.
Timing suggestions often reflect study conditions rather than proven routines.
In several studies, participants took L-theanine about 30 to 60 minutes before bedtime. This timing simply follows research design and does not serve as a universal recommendation.
Some studies have looked at daytime use of L-theanine for promoting calmness or focus. Any connection between daytime use and nighttime sleep should be seen as observational, not a guaranteed effect.
Doses in scientific studies vary, and individual needs can differ. Research shows a range of amounts have been tested for sleep and focus-related outcomes. It’s important to remember that no single dosage guarantees results for everyone.
Studies have investigated L-theanine in a range of 100 to 400 mg per dose to observe its effects on attention and reaction time. In a double-blind, placebo-controlled crossover study involving healthy young adults, doses between 100 and 200 mg were associated with improved simple reaction times, while higher doses up to 400 mg did not show the same effect across more complex attention tasks.
This suggests that 100–400 mg represents the range most often examined in research, though effectiveness may depend on task type and individual response rather than a fixed optimal dose (Dassanayake et al., 2023)¹.
It is best to discuss dosage with a healthcare professional, particularly if you take prescription medications or manage blood pressure concerns. Adjusting intake on your own may not be appropriate for everyone.
L-theanine has been studied in combination with other nutrients and plant extracts. In one randomized, placebo-controlled trial, a supplement containing magnesium, B vitamins, rhodiola, and green tea extract (providing L-theanine) was tested in adults who reported chronic stress. After 28 days, participants who took the combination showed lower stress scores on the Depression Anxiety Stress Scale compared with those who took a placebo.
The study also observed improvements in measures related to sleep quality and pain perception, though these findings were specific to the multi-ingredient formula, not to L-theanine alone. Because it is difficult to separate the effects of each ingredient, using such combinations should be done with professional guidance (Noah et al., 2022)⁴.
Findings beyond sleep remain preliminary and vary across studies. Some evidence suggests that L-theanine may influence mood, focus, and stress levels in specific groups. These effects are modest and not consistent across all research.
Research has explored how L-theanine may influence responses to psychological stress and feelings of anxiety. A review of clinical studies found that daily doses between 200 and 400 mg for up to eight weeks were generally safe and were associated with reduced self-reported stress and anxiety levels in both short- and long-term settings. However, these findings come from specific study conditions, and more controlled research is needed to confirm consistent results across larger populations (Sakamoto et al., 2019)³.
L-theanine has been examined for its potential to support relaxed alertness or steady attention. Results differ and may depend on caffeine intake, dosage, and other conditions. The research does not confirm consistent improvements in everyday cognitive functions.
Reported shifts in mood or calmness come from small or short-term studies. These do not represent predictable outcomes for everyone and should be understood as exploratory research results.
Short-term use of L-theanine for sleep has generally been well tolerated among healthy adults in available research. Most studies report only mild or temporary effects that resolve on their own. However, data on long-term or high-dose use remain limited.
In research and consumer reports, L-theanine has generally been well tolerated, though a few mild effects have been mentioned. These are uncommon and vary by individual:
Headache or light discomfort in the head
Mild nausea or upset stomach
Digestive discomfort when taken without food
Occasional fatigue or dizziness was reported in some users
These experiences were reported by a small number of participants and do not suggest that most people will experience them.
While L-theanine is considered safe for most healthy adults, certain groups are encouraged to consult a healthcare professional before use, mainly as a precaution:
People who are pregnant or breastfeeding
Individuals with low blood pressure or heart-related conditions
Anyone taking prescription medications, especially sedatives or blood pressure drugs
People with ongoing medical conditions or those preparing for surgery
These precautions are based on general safety practices and limited long-term data, not on evidence of specific harm.
Because L-theanine may influence the central nervous system or blood pressure in some research, a theoretical risk of interaction exists when used with sedatives or antihypertensive medications. Consulting a clinician before adding L-theanine to a supplement routine is advised.
While L-theanine is most often consumed through supplements, it also occurs naturally in certain foods and beverages. The amount can vary depending on the source and preparation method:
Green tea (Camellia sinensis): The richest natural source of L-theanine, especially varieties like matcha and gyokuro.
Black tea: Contains lower amounts of L-theanine compared to green tea, as some of it breaks down during oxidation.
White tea: Offers moderate levels of L-theanine with a lighter flavor and less caffeine.
Certain mushrooms (e.g., Boletus badius): Trace amounts of L-theanine have been detected in some edible mushrooms, though much less than in tea.
While these foods can contribute small amounts of L-theanine to your diet, supplements provide a consistent, measured dose for research or targeted use.
Melatonin and L-theanine have both been studied for their potential roles in improving sleep, but they appear to work through different mechanisms. A randomized, double-blind, placebo-controlled trial compared the effects of oral melatonin (3 mg) and oral L-theanine (200 mg) on sleep among cancer patients with insomnia. Results showed that melatonin produced greater improvements on the Athens Insomnia Scale than L-theanine after 14 days of use. However, participants taking L-theanine still experienced better sleep outcomes than those in the placebo group, suggesting it may have a modest sleep-supporting effect within this population. These findings indicate that while melatonin demonstrated stronger results in this study, both substances showed potential for improving certain aspects of sleep when compared to placebo (Kurdi et al., 2024)².
Research on L-theanine for sleep shows promising but limited results. In several small, controlled trials, L-theanine has been linked to relaxation and modest improvements in self-reported sleep quality. However, findings vary between studies, and there is no guarantee of the same effects for everyone.
L-theanine appears to work by supporting calmness and mental focus rather than causing sedation. For some people, this gentle relaxation may help reduce the mental tension that delays sleep. Most studies have used doses between 100 and 400 mg, often taken 30–60 minutes before bed, but these ranges come from research settings—not universal recommendations.
Short-term use has generally been well tolerated, with few mild side effects reported. Still, people who are pregnant, breastfeeding, managing blood pressure, or taking sedatives should speak with a healthcare professional before adding L-theanine to their routine.
While it is not a proven sleep aid, L-theanine may be a supportive addition to a broader sleep wellness routine, especially when paired with consistent bedtime habits, reduced screen time, and a balanced diet. Those seeking to improve sleep quality can consider adding L-theanine to their nightly routine alongside other healthy sleep practices, with guidance from a healthcare professional.
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How much L-theanine should I take for sleep?
Research has used 100–400 mg of L-theanine per dose; speak with a clinician about what may fit your situation.
Is L-theanine better than melatonin for sleep?
They serve different purposes in research. Which is “better” depends on personal goals and medical context.
When is the best time to take L-theanine?
In some studies, participants took it 30–60 minutes before bed, but this reflects research design rather than a universal recommendation.
Can I take L-theanine every night?
Short-term use has been generally well tolerated; for ongoing use, consult a healthcare provider.
Are there any side effects of taking L-theanine before bed?
Some studies have reported mild effects such as headache or nausea. Those with blood pressure concerns or taking medication should consult a clinician first.
References
Dassanayake TL, Wijesundara D, Kahathuduwa CN, Weerasinghe VS. Dose-response effect of L-theanine on psychomotor speed, sustained attention, and inhibitory control: a double-blind, placebo-controlled, crossover study. Nutr Neurosci. 2023 Nov;26(11):1138-1146. doi: 10.1080/1028415X.2022.2136884. Epub 2022 Oct 20. PMID: 36263942.
Kurdi MS, As A, Ladhad DA, Mitragotri MV, Baiju A. Comparison Between Efficacy of Oral Melatonin and Oral L-theanine in Improving Sleep in Cancer Patients Suffering From Insomnia: A Randomised Double-blinded Placebo-controlled Study. Indian J Palliat Care. 2024 Apr-Jun;30(2):176-181. doi: 10.25259/IJPC_89_2023. Epub 2024 May 3. PMID: 38846134; PMCID: PMC11152521.
Lopes Sakamoto F, Metzker Pereira Ribeiro R, Amador Bueno A, Oliveira Santos H. Psychotropic effects of L-theanine and its clinical properties: From the management of anxiety and stress to a potential use in schizophrenia. Pharmacol Res. 2019 Sep;147:104395. doi: 10.1016/j.phrs.2019.104395. Epub 2019 Aug 11. PMID: 31412272.
Noah L, Morel V, Bertin C, Pouteau E, Macian N, Dualé C, Pereira B, Pickering G. Effect of a Combination of Magnesium, B Vitamins, Rhodiola, and Green Tea (L-Theanine) on Chronically Stressed Healthy Individuals-A Randomized, Placebo-Controlled Study. Nutrients. 2022 Apr 29;14(9):1863. doi: 10.3390/nu14091863. PMID: 35565828; PMCID: PMC9102162.