Glycine
3 g · Daily, PM
Robert
Founder, F*CK Getting Old — independent researcher, not a medical professional.
Last reviewed · 2 cited sources
Evidence
- Human Studies
- 15
- Animal Studies
- 20
- Clinical Status
- Dietary Supplement
- Confidence
- Low
- Long-Term Safety
- Very well-tolerated — an amino acid with a long history of dietary and clinical use; dedicated sleep-specific trials are fewer than for melatonin
What this score is: a measure of how much research exists and how far along it is (animal-only vs. human trials, research-stage vs. FDA approved) — not how safe, effective, or worth trying a compound is. A low score usually means “early stage” or “understudied,” not “bad.” A high score doesn’t mean “better” for your goals than a lower-scored one.
This is not my personal rating of the compound, not a recommendation, and not medical advice. It’s a general research synthesis for informational purposes only, not a live literature count. See the linked research and talk to a licensed clinician before making decisions based on it.
Mechanism
A non-essential amino acid studied for improving subjective sleep quality, possibly through mild core-body-temperature lowering and NMDA receptor modulation. Evidence comes from a modest number of small trials, mostly from Japanese researchers, and is far thinner than the melatonin literature.
Common Protocols
- 3 g, 30–60 minutes before bed
Side Effects
- Generally very well-tolerated
- Mild GI upset in some people at higher doses
Interactions
- No well-characterized interactions
Practical Details
- Cost
- $
- Typical Dose
- 3 g
- Storage
- Store in a cool, dry place
Key Studies & Reviews
- Bannai M, Kawai N (2012). New therapeutic strategy for amino acid medicine: glycine improves the quality of sleep. J Pharmacol Sci. PMID 22293292.
- Fan Z et al. (2026). Glycine bioavailability and sleep-related outcomes following oral glycine and collagen supplementation: a scoping review. J Diet Suppl. PMID 42687500.
Search the Research
Glycine FAQ
What is the typical Glycine dosage?
Commonly reported protocols: 3 g, 30–60 minutes before bed. Our reference entry uses 3 g, Daily, PM. These reflect protocols reported in research and user communities, not a medical recommendation — dosing should be decided with a clinician.
What are the side effects of Glycine?
Reported side effects include: Generally very well-tolerated; Mild GI upset in some people at higher doses.
Is Glycine FDA approved?
Glycine is sold as a dietary supplement. The FDA does not approve supplements for safety or effectiveness before they are sold, so third-party tested brands are worth seeking out.
How much research is there on Glycine?
Our evidence profile counts roughly 15 human and 20 animal studies, with low overall confidence. Long-term safety: Very well-tolerated — an amino acid with a long history of dietary and clinical use; dedicated sleep-specific trials are fewer than for melatonin.
Does Glycine interact with other drugs or supplements?
No well-characterized interactions.
Related compounds
Amino acid studied for subjective sleep quality