Last update
3/26/2026
Reviewed By
Overview
SCIENTIFIC SCORE
Likely Ineffective
Based on 2 Researches
4
USERS' SCORE
Good
Based on 12 Reviews
8.2
Supplement Facts
Serving Size: 1 Veggie Capsule
Serving Per Container: 90
Amount Per Serving
%DV
L-Theanine (Suntheanine®)
150 mg
†
Top Medical Research Studies
4
Insufficient evidence for L-theanine
We examined the effectiveness of various sleep medications, including L-theanine, for children and adolescents with ADHD. Out of 337 articles, only five were relevant.
While L-theanine showed some improvement in sleep efficiency, it did not significantly reduce sleep latency or increase overall sleep time. Other medications like clonidine and melatonin showed more promising results, reducing insomnia more effectively.
Overall, the lack of robust evidence for L-theanine suggests that more research is needed to confirm these findings and guide treatment options.
While L-theanine showed some improvement in sleep efficiency, it did not significantly reduce sleep latency or increase overall sleep time. Other medications like clonidine and melatonin showed more promising results, reducing insomnia more effectively.
Overall, the lack of robust evidence for L-theanine suggests that more research is needed to confirm these findings and guide treatment options.
Read More
4
In our 10-week study with 46 participants diagnosed with Generalized Anxiety Disorder (GAD), we aimed to see if L-theanine could enhance sleep and reduce anxiety when combined with standard antidepressants.
While L-theanine didn’t significantly lower anxiety or insomnia severity compared to a placebo, participants on L-theanine did report feeling more satisfied with their sleep quality. Particularly, those experiencing non-clinical insomnia symptoms noted better outcomes.
These findings suggest that while L-theanine may not be a strong treatment for anxiety, it could have potential for improving sleep satisfaction.
While L-theanine didn’t significantly lower anxiety or insomnia severity compared to a placebo, participants on L-theanine did report feeling more satisfied with their sleep quality. Particularly, those experiencing non-clinical insomnia symptoms noted better outcomes.
These findings suggest that while L-theanine may not be a strong treatment for anxiety, it could have potential for improving sleep satisfaction.
Read More
Most Useful Reviews
9
Great for insomnia relief
48 people found this helpful
I started taking Theanine to help with my insomnia. Previously, I had difficulty finding an effective solution, and my doctor wasn't helpful. After starting Theanine, the nightly 3 AM awakenings ceased, and I no longer experience joint pain. I also noticed a reduction in my high blood pressure after taking it. After a week, my knees felt better than they have in a year, prompting me to increase my intake frequency.
Read More
9
Much calmer
2 people found this helpful
I follow my doctor's directions for insomnia and take one capsule at lunchtime. The result has been noticeably calmer days.
Read More
9
Pre-bedtime success
Working best for my insomnia, taking this before bedtime helps me. I plan to try it alongside GABA to see the results as experts suggest. Delivery from iHerb is punctual, and the packaging is excellent.
Read More
Medical Researches
SCIENTIFIC SCORE
Likely Ineffective
Based on 2 Researches
4
- All Researches
4
In our 10-week study with 46 participants diagnosed with Generalized Anxiety Disorder (GAD), we aimed to see if L-theanine could enhance sleep and reduce anxiety when combined with standard antidepressants.
While L-theanine didn’t significantly lower anxiety or insomnia severity compared to a placebo, participants on L-theanine did report feeling more satisfied with their sleep quality. Particularly, those experiencing non-clinical insomnia symptoms noted better outcomes.
These findings suggest that while L-theanine may not be a strong treatment for anxiety, it could have potential for improving sleep satisfaction.
While L-theanine didn’t significantly lower anxiety or insomnia severity compared to a placebo, participants on L-theanine did report feeling more satisfied with their sleep quality. Particularly, those experiencing non-clinical insomnia symptoms noted better outcomes.
These findings suggest that while L-theanine may not be a strong treatment for anxiety, it could have potential for improving sleep satisfaction.
Read More
4
Insufficient evidence for L-theanine
We examined the effectiveness of various sleep medications, including L-theanine, for children and adolescents with ADHD. Out of 337 articles, only five were relevant.
While L-theanine showed some improvement in sleep efficiency, it did not significantly reduce sleep latency or increase overall sleep time. Other medications like clonidine and melatonin showed more promising results, reducing insomnia more effectively.
Overall, the lack of robust evidence for L-theanine suggests that more research is needed to confirm these findings and guide treatment options.
While L-theanine showed some improvement in sleep efficiency, it did not significantly reduce sleep latency or increase overall sleep time. Other medications like clonidine and melatonin showed more promising results, reducing insomnia more effectively.
Overall, the lack of robust evidence for L-theanine suggests that more research is needed to confirm these findings and guide treatment options.
Read More
User Reviews
USERS' SCORE
Good
Based on 12 Reviews
8.2
- All Reviews
- Positive Reviews
- Negative Reviews
9
Great for insomnia relief
48 people found this helpful
I started taking Theanine to help with my insomnia. Previously, I had difficulty finding an effective solution, and my doctor wasn't helpful. After starting Theanine, the nightly 3 AM awakenings ceased, and I no longer experience joint pain. I also noticed a reduction in my high blood pressure after taking it. After a week, my knees felt better than they have in a year, prompting me to increase my intake frequency.
Read More
9
Much calmer
2 people found this helpful
I follow my doctor's directions for insomnia and take one capsule at lunchtime. The result has been noticeably calmer days.
Read More
9
Pre-bedtime success
Working best for my insomnia, taking this before bedtime helps me. I plan to try it alongside GABA to see the results as experts suggest. Delivery from iHerb is punctual, and the packaging is excellent.
Read More
8
Very effective
2 people found this helpful
This product is effective for insomnia.
Read More
7.5
Aids sleep
2 people found this helpful
I followed a regimen for insomnia, and it helped me fall asleep.
Read More
Frequently Asked Questions
2
Ineffective treatment
I bought it to tackle insomnia, but it didn't help at all.
4
In our 10-week study with 46 participants diagnosed with Generalized Anxiety Disorder (GAD), we aimed to see if L-theanine could enhance sleep and reduce anxiety when combined with standard antidepressants.
While L-theanine didn’t significantly lower anxiety or insomnia severity compared to a placebo, participants on L-theanine did report feeling more satisfied with their sleep quality. Particularly, those experiencing non-clinical insomnia symptoms noted better outcomes.
These findings suggest that while L-theanine may not be a strong treatment for anxiety, it could have potential for improving sleep satisfaction.
While L-theanine didn’t significantly lower anxiety or insomnia severity compared to a placebo, participants on L-theanine did report feeling more satisfied with their sleep quality. Particularly, those experiencing non-clinical insomnia symptoms noted better outcomes.
These findings suggest that while L-theanine may not be a strong treatment for anxiety, it could have potential for improving sleep satisfaction.
4
Insufficient evidence for L-theanine
We examined the effectiveness of various sleep medications, including L-theanine, for children and adolescents with ADHD. Out of 337 articles, only five were relevant.
While L-theanine showed some improvement in sleep efficiency, it did not significantly reduce sleep latency or increase overall sleep time. Other medications like clonidine and melatonin showed more promising results, reducing insomnia more effectively.
Overall, the lack of robust evidence for L-theanine suggests that more research is needed to confirm these findings and guide treatment options.
While L-theanine showed some improvement in sleep efficiency, it did not significantly reduce sleep latency or increase overall sleep time. Other medications like clonidine and melatonin showed more promising results, reducing insomnia more effectively.
Overall, the lack of robust evidence for L-theanine suggests that more research is needed to confirm these findings and guide treatment options.
References
- Sarris J, Byrne GJ, Cribb L, Oliver G, Murphy J, et al. L-theanine in the adjunctive treatment of generalized anxiety disorder: A double-blind, randomised, placebo-controlled trial. J Psychiatr Res. 2019;110:31. 10.1016/j.jpsychires.2018.12.014
- Barrett JR, Tracy DK, Giaroli G. To sleep or not to sleep: a systematic review of the literature of pharmacological treatments of insomnia in children and adolescents with attention-deficit/hyperactivity disorder. J Child Adolesc Psychopharmacol. 2013;23:640. 10.1089/cap.2013.0059
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