Glycine vs L-Theanine for sleep
Short answer: For sleep, more users report improvement with Glycine — 87% of 255 reports, versus 78% of 370 for L-Theanine.
Glycine has 392 meta-analyses and 620 randomized trials on PubMed; L-Theanine has 18 and 78.
Based on 695 reports about Glycine and 3,475 about L-Theanine. Not medical advice.
| Glycine Supplement | L-Theanine Supplement | |
|---|---|---|
| Users say it helped | 70%helped299 reports · high confidence | 65%helped1,807 reports · high confidence |
| Verdict | Mostly positive | Mostly positive |
| Research | AResearch: Strong | AResearch: Strong |
| Meta-analyses / RCTs | 392 / 620 | 18 / 78 |
| Mainly used for | ||
| Anxiety % reporting improvement | 78% (60) | 91% (1289) |
| Sleep % reporting improvement | 87% (255) | 78% (370) |
| Focus % reporting improvement | 62% (13) | 88% (501) |
| Mood % reporting improvement | 87% (39) | 77% (223) |
| Energy % reporting improvement | 94% (17) | 68% (97) |
| Common side effects | vivid dreams, drowsiness, fatigue, brain fog | drowsiness, vivid dreams, fatigue, headache |
| Typical dose reported | 2 g / daily | 200 mg / bedtime |
In studies using high-throughput metabolomics, several blood amino acids appear to be consistently associated with the risk of developing type 2 diabetes.
Diabetes Care, 2016 ↗“2 grams with 200mg magnesium before bed gives me crazy good sleep. Crazy vivid dreams.”
This meta-analysis provides evidence that theanine plus caffeine, and theanine alone, could be beneficial for cognitive and mood outcomes. More research using tea beverages or tea-equivalent bioactive doses and research in free-living participants is needed.
Nutr Rev, 2025 ↗“This morning was my first time taking this combination along with my other daily vitamins and wow, what a difference it has made in my overall mood and anxiety!”
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Percentages come from first-hand user reports and are not clinical outcomes. Talk to a doctor before starting, stopping or combining anything. How we rate