Medical disclaimer: CalmVerdict summarizes what people say about supplements on Reddit. It is not medical advice, and nothing here is meant to diagnose, treat, cure, or prevent any disease. These statements have not been evaluated by the Food and Drug Administration. Talk to your doctor or pharmacist before starting a supplement, especially if you take an antidepressant or other medicine, are pregnant, or have a medical condition. Do not stop or change prescribed medicine on your own. If you are in crisis or thinking about suicide, call or text 988 (US) or your local emergency number. Full disclaimer.

Glycine vs L-theanine

On Reddit, owners rate L-theanine higher overall (4.0 vs 3.0). Scores summarize self-reported experiences and are not evidence that either will work for you.

GlycineL-theanine
Typepowder or capsulescapsules
CalmVerdict score3.04.0
Owner sentiment3.23.5
Recommendations1.04.8
Tolerability4.04.4
Owner comments77330
Rated comments42196
Unwanted effects reported19%14%
Top praiseCalming effect, Dose & timingCalming effect, Dose & timing
Top complaintsSide effects, Calming effectSide effects, Calming effect

By concern

ContextGlycineL-theanine
Anxiety & worry5 of 19 positive35 of 71 positive
Low mood3 of 16 positive13 of 30 positive
Everyday stress4 of 11 positive25 of 52 positive
Panic attacks0 of 3 positive11 of 20 positive
Rumination & intrusive thoughts1 of 7 positive2 of 4 positive
Physical tensionToo few comments3 of 7 positive

What owners say about Glycine

5/5 Taste & form

“Glycine is what I swear by. One teaspoon with green tea in the morning and one before sleep. I took it primarily for collagen but with time noticed the effect of calmness, it is now harder for me to become agitated and stressed.”

owner comment via r/Supplements · 2026-06-04 · 18 upvotes
2/5 Side effects

“i experience a paradoxical effect to glycine, it gives me extreme anxiety & insomnia.”

owner comment via r/Supplements · 2026-09-08 · 17 upvotes
3/5 MoodSide effects

“I've also had some very weird reactions to iron bisglycinate that are pretty confounding considering the amount of glycine in that is \*extremely\* low compared to the amounts we get in food.”

owner comment via r/Nootropics · 2026-10-23 · 2 upvotes

Full Glycine page →

What owners say about L-theanine

2/5 Calming effect

“Theanine, because I had tried it for evening calm and it didn't do anything for me.”

owner comment via r/Supplements · 2026-08-05 · 50 upvotes
4/5 Calming effectTaste & form

“The I found a liquid L theanine and that made all the difference in the world.”

owner comment via r/Supplements · 2026-09-12 · 13 upvotes
4/5 Calming effectFalling asleep

“l-theanine is the only one that's worked for me.”

owner comment via r/Nootropics · 2026-09-17 · 12 upvotes

Full L-theanine page →

Talk to a doctor or pharmacist before switching or combining supplements, particularly if you take other medicines.