Glycine for Sleep: What the Trials Show and What It Costs
Glycine before bed: the small trials behind the claim, their sample sizes and funding ties, the dose they used, and a cost check against Thorne's price.
Researched from published studies and manufacturer specifications, checked .
We have not tested products ourselves. How we researchQuick verdict
Glycine before bed has a small, mostly Japanese trial base, with the best-described crossover trial analysing 7 people and several authors working at the glycine maker Ajinomoto. The reported effects are on how rested people felt and on sleep onset in a few lab measures, not on any health outcome. The dose used in Bannai 2012 was 3 g before bed. Evidence grade: Weak.
Talk to your doctor first. This is general information, not medical advice. Supplements and devices can interact with medicines and health conditions. We quote study protocols for context and do not recommend doses.
The short answer: glycine, an amino acid, has a small set of trials suggesting people feel their sleep is better after taking it before bed. They are tiny and short. The best-described one is a crossover trial of 10 men enrolled and 7 analysed, run at the glycine maker Ajinomoto. The dose used in Bannai 2012 was 3 g before bedtime. No trial shows a health benefit beyond how rested people felt, so the evidence grade is Weak. This page quotes trial doses, not advice; talk to your doctor before starting a supplement.
The trials, one by one
| Trial | Design | Dose used | Result | Caveats |
|---|---|---|---|---|
| Bannai 2012 | Randomised single-blind crossover; sleep restricted to 25% less than usual for three nights | 3 g or placebo, 30 min before bed | Significantly less fatigue and better psychomotor vigilance the next day on the authors’ tests, only a tendency toward less sleepiness; no effect on plasma melatonin | 10 men enrolled (employees of Ajinomoto), 7 analysed (1 dropped out, 2 excluded for medication); authors at Ajinomoto, which makes glycine; the paper declares no conflict and says it was supported in part by a Japanese research-promotion programme (full text) |
| Yamadera 2007 | Volunteers with sleep complaints, with polysomnography, per Bannai 2012 | 3 g before bedtime, per Bannai 2012 | Bannai 2012 describes it as showing a shorter sleep latency on polysomnography | Abstract and sample size not available to us; one author, Bannai, is an Ajinomoto researcher in the 2012 paper, other affiliations not checked |
| Inagawa 2006 | Subjective sleep-quality trial in people with sleep complaints, per Bannai 2012 | 3 g before bedtime, per Bannai 2012 | Bannai 2012 describes it as showing better subjective sleep quality | Abstract not available to us at source |
| GeroScience review 2024 | Systematic review of glycine in adults (18 studies in healthy people, 34 in patients) | Various | The review says longer-term glycine improved sleep in healthy populations, but “these studies had small sample sizes with a high risk of bias” | Glycine was given for up to 14 days in healthy people and up to 4 months in patients; the abstract reports no conflict of interest |
| Kawai 2015 | Rodent mechanism study | n/a | Glycine’s sleep-promoting and body-temperature-lowering effect depends on NMDA receptors in the suprachiasmatic nucleus | Animal; not evidence of human benefit |
Reading across: the human evidence is a handful of small trials from one research group, measuring how people felt and short-term sleep measures. Objective data (polysomnography) exist in one trial, as described by Bannai 2012. None followed people for more than a few days, and we found no large independent replication. A 2012 review by the same group proposes a mechanism, lower core body temperature at sleep onset, that rests largely on rat data.
What it costs at the trial dose
Costs are arithmetic on 3 g a day, the dose used in Bannai 2012 (not a recommendation), from the maker’s page or our cost per study dose dataset.
| Product | Price | Per month at 3 g/day | Testing stated |
|---|---|---|---|
| Thorne Glycine, 250 capsules (1 g per 2 capsules) | $31 | $22.32 (6 capsules, 3 servings, a day; a 250-capsule bottle is 125 servings, per Thorne’s page on 2 Oct) | none stated |
| Double Wood Glycine | $19.95 | not calculated: capsule or serving count not readable | self-stated third-party testing with a certificate, no named certifier |
| Bulk Supplements Glycine Powder, 500 g | $25.97 | not calculated: serving size not read; if the tub is pure glycine, 500 g is about 166 servings of 3 g, about $4.68 a month (our arithmetic) | none stated |
Prices were read on 28 to 29 Sept 2026 for Double Wood and Bulk Supplements and 2 Oct 2026 for Thorne; Bulk Supplements and Double Wood pages were rate-limited to our reader on 2 Oct and not re-read. The spread is large because capsules cost far more per gram than powder. Whether a bottle contains what it says is a separate question; see third-party testing explained.
What else to try first
Glycine’s trial evidence is thinner than the basics. See the sleep hygiene protocol, best sleep tools, and magnesium for another popular bedtime supplement graded on the same rubric. If sleep trouble is persistent, see a clinician: insomnia can have causes a supplement will not address.
Method note
Researched from PubMed abstract records, the open full text of Bannai 2012, and brand pages, checked 2 Oct 2026. Two of the older trials could not be read at source and are described from the same group’s 2012 full text, and the page says so. We did not test any product. Grades are our judgement using the published rubric. General information, not medical advice.
Common questions
Does glycine help you sleep?
Small trials report better subjective sleep quality and shorter time to sleep onset, but they are tiny, short, and in part run by a glycine manufacturer. A systematic review of glycine in adults (published online 2023, in GeroScience 2024) said the sleep studies in healthy people had small samples and a high risk of bias. We grade the evidence Weak.
How much glycine did the studies use?
Dose used in Bannai 2012: 3 g taken before bedtime (30 minutes before). Its authors say the same group's earlier trials used 3 g too, a figure we could not check in those papers. That is what the trials gave, not a recommendation.
Is glycine safe?
That review covered studies of up to 14 days in healthy adults and up to 4 months in patients, so long-term safety in healthy people is not established. Talk to your doctor, especially if you take prescription medicines.
Sources
- Bannai 2012, effects of glycine on subjective daytime performance in partially sleep-restricted healthy volunteers (Front Neurol) checked 2 Oct 2026
- Bannai 2012, full text (participants, design, affiliations, funding) checked 2 Oct 2026
- Yamadera 2007, glycine ingestion improves subjective sleep quality, correlating with polysomnographic changes (Sleep Biol Rhythms), abstract not available to us at source; described from the same group's 2012 full text checked 2 Oct 2026
- Inagawa 2006, subjective effects of glycine ingestion before bedtime on sleep quality (Sleep Biol Rhythms); abstract not available to us at source; described from the same group's 2012 full text checked 2 Oct 2026
- Glycine administration and physiological systems in human adults, systematic review (GeroScience 2024) checked 2 Oct 2026
- Bannai and Kawai 2012, new therapeutic strategy for amino acid medicine: glycine improves the quality of sleep (J Pharmacol Sci) checked 2 Oct 2026
- Kawai 2015, sleep-promoting and hypothermic effects of glycine are mediated by NMDA receptors in the suprachiasmatic nucleus (Neuropsychopharmacology; rodent mechanism) checked 2 Oct 2026
- Thorne, Glycine product page ($31 for 250 capsules, 125 servings, 1 g per 2-capsule serving) checked 2 Oct 2026
- Longevity Intel cost per study dose dataset (Double Wood $19.95 and Bulk Supplements $25.97 read 28 to 29 Sept 2026) checked 2 Oct 2026
Update log
- New page: the glycine-for-sleep trials with sample sizes, design and funding ties, and a cost check at the dose the trials used.
Data and comparisons
- Magnesium evidence record
Required for 300+ enzymatic reactions
- Vitamin D3 evidence record
Deficiency is endemic (over 40% of Western adults) and associated with higher all-cause mortality
- Magnesium Forms Compared: Glycinate vs L-Threonate vs Malate
Glycinate default; threonate for brain
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