Amino acid · Fact sheet
Glycine
Glycine is an amino acid with small human studies of sleep and next-day fatigue. These early results do not establish treatment of chronic insomnia or the benefits of glycine alone for healthy aging.
What is Glycine?
Glycine is a building block for proteins and glutathione and also participates in nervous-system signaling. Being naturally present in the body does not settle the benefits or risks of supplementation.
Benefits people look for
Better sleep, reduced next-day fatigue, collagen support, and healthy aging drive interest. Studies combining glycine with N-acetylcysteine cannot isolate glycine’s contribution.
What the evidence supports
- Small studies reported improved subjective sleep or reduced next-day fatigue in selected conditions.
- These results do not establish a treatment for chronic insomnia or prove an anti-aging benefit.
All research areas
- Sleep quality
- Daytime fatigue after sleep restriction
- Glutathione-related metabolism
Anecdotal reports & lived experiences
Reports describe what someone noticed. They cannot establish cause, typical results, or how often a side effect happens.
More consistently restorative sleep
A person with recurring sleep difficulties described more good nights and subjectively deeper, more restorative sleep after starting glycine.
Sleep stages were not independently measured. The report is unblinded and does not establish treatment of a sleep disorder.
Read the positive sleep account ↗Earlier waking and afternoon tiredness
Another person described shorter sleep and afternoon fatigue after starting glycine, then more usual sleep on a day without it.
The poster also described irregular sleep, epilepsy and prescription medicines. These confounders prevent a confident causal conclusion.
Read the contrasting sleep account ↗Side effects & risks
- The short sleep studies cannot establish uncommon adverse effects or long-term safety.
- Safety and effects of multi-ingredient products cannot be inferred from isolated-glycine studies.
This is a summary of the cited evidence, not a complete product label. A lack of human safety data does not establish safety.
Clinical research: how strong is it?
Early human evidenceThe sleep literature cited here uses small, short experiments, including sleep restriction. Findings on subjective fatigue or a laboratory sleep night need confirmation in larger clinical populations.
Selected research to read
Small short-term human experiment; animal circadian experiments reported separately.
Small human sleep study published in Sleep and Biological Rhythms.
FDA approval & research status
Glycine has no FDA-approved drug indication for the wellness uses discussed here. Supplement availability is not premarket FDA approval of effectiveness or safety.
No FDA-approved use is documented in the records summarized on this page.
Supplement research is not FDA drug approval
Glycine has no FDA-approved drug indication for the wellness uses discussed here. Supplement availability is not premarket FDA approval of effectiveness or safety.
This summarizes the cited product or research record. Trial phases do not establish successful completion of earlier stages, and a stopped program is not ongoing development. Approval applies only to the labeled product, use and population.
What we still don’t know
- Durable improvement in diagnosed sleep disorders
- Long-term outcomes from glycine alone
- Effects in different age groups and with other medicines
The takeaway
These results do not establish a treatment for chronic insomnia or prove an anti-aging benefit.
Sources & further reading
Medical evidence and regulatory sources are listed here. Personal reports are linked separately in the experiences section.
- 1pubmedGlycine and daytime performance after sleep restriction
Small short-term human experiment; animal circadian experiments reported separately.
- 2journalGlycine and subjective and polysomnographic sleep measures
Small human sleep study published in Sleep and Biological Rhythms.
- 3fdaFDA: what approval means for supplements
Dietary supplements are not approved by FDA for safety and effectiveness before marketing.