Ingredient Reference
Glycine: Chemistry, Sources, Studied Amounts and Safety
What glycine is, how the body makes and uses it, how to read glycine on a label, what amounts human studies used, and who should ask a clinician first.
Join the WaitlistGlycine on the Label
How much glycine our product holds, taken from its product page.
Planned formula. Coming soon: join the waitlist on the product page; no payment is taken. How to use it (product page): stir 1 scoop into 8 oz of plain or sparkling water and drink it 30 to 60 minutes before bed. Do not take more than 1 scoop a day. How this compares with research: 3 g is the amount given before bed in the human sleep studies below.
Glycine at a Glance
| Item | Details |
|---|---|
| Names | Glycine; aminoacetic acid; aminoethanoic acid; abbreviated Gly or G. CAS 56-40-6. |
| Formula | C2H5NO2 (NH2CH2COOH), 75.07 g/mol. |
| Classification | Nonessential amino acid, also listed as conditionally essential. |
| Made in the body | About 3 g a day, mostly from serine. |
| Food sources | Protein foods, richest in collagen and gelatin. Typical intake 1.5 to 3 g a day. |
| Amounts in studies | 3 g before bed in sleep studies; 100 mg per kg a day with NAC in a 16 week trial. |
| Main cautions | Clozapine, pregnancy and nursing, under 18, other prescription medicines. |
| US status | Dietary ingredient (amino acid) in supplements; approved food additive for limited uses (21 CFR 172.812). |
Here for sleep? Timing, the body temperature idea and how glycine sits with other evening ingredients are covered in Glycine for Sleep: Does It Work, How Much and When to Take It. This page sticks to reference facts.
Chemistry, Synthesis and Roles
Glycine is the smallest of the amino acids used to build protein. Its side chain is a single hydrogen atom, so its central carbon carries two identical hydrogens; unlike the other protein amino acids, it has no left- and right-handed (L and D) forms.
How the body makes it
Most glycine is made from the amino acid serine by the enzyme serine hydroxymethyltransferase. A 2009 analysis put synthesis at about 3 g a day, with serine supplying more than 85%, and dietary intake at 1.5 to 3 g a day. The authors estimated that total needs, including collagen turnover, could exceed that supply by about 10 g a day in a 70 kg adult, and described glycine as possibly semi-essential. MedlinePlus lists glycine as nonessential and also as conditionally essential, meaning needs can rise during illness and stress.
What the body uses it for
- Protein: collagen has glycine at every third position of its chain, which is why collagen and gelatin are rich sources.
- Glutathione: one of its three building blocks, with glutamate and cysteine.
- Creatine: with arginine and methionine, a raw material for the roughly 1 g of creatine the liver and kidneys produce daily.
- Signaling: a neurotransmitter, and a co-agonist at NMDA receptors in the brain.
Forms and How to Read a Label
| Form | What it is | What to know |
|---|---|---|
| Free-form glycine powder | The amino acid on its own | Amount listed as glycine; this is the form in the sleep studies. |
| Mineral glycinates | Minerals such as magnesium bound to glycine | Labels list the mineral amount, not the glycine; the glycine carried is a small fraction of 3 g. |
| Collagen and gelatin | Whole proteins rich in glycine | Glycine content is usually not stated per serving. |
| GlyNAC products | Glycine paired with N-acetylcysteine | Studied as a pair; check each amount separately. |
What to check on a label
- The word "glycine" as its own line, rather than only inside a mineral name ending in "glycinate".
- The amount in mg or g: 3,000 mg and 3 g are the same.
- Serving size in scoops or capsules; capsules hold far less powder than a scoop.
- Blends: whether glycine is listed with its own amount.
Keep glycine powder closed, cool and dry, and use it by the label date.
Glycine in Human Studies
Human trials and one review. Rat work on the mechanism is noted below the table and is separate from human results.
| Study | Who | Amount a day | Length | Measured | Result |
|---|---|---|---|---|---|
| Inagawa 2006, Sleep Biol Rhythms | Volunteers with sleep quality complaints; randomized, double-blind crossover | 3 g before bed, or placebo | Not given in abstract | Next-morning feelings by sleep and fatigue questionnaires | Better ratings for fatigue, liveliness and clear-headedness on waking |
| Yamadera 2007, Sleep Biol Rhythms | Volunteers with ongoing unsatisfactory sleep | 3 g before bed | Not given in abstract | Polysomnography, sleep quality, daytime sleepiness, memory tasks | Shorter time to sleep onset and slow-wave sleep; sleep architecture unchanged; better memory recognition |
| Bannai 2012, Front Neurol | 7 healthy men aged 30 to 61 (10 enrolled), sleep cut 25% for 3 nights; single-blind crossover | 3 g, 30 minutes before bed, or placebo | 3 nights per condition | Sleepiness and fatigue scales, reaction time tests | Lower fatigue and faster psychomotor vigilance on day 1 |
| Sekhar 2011, Am J Clin Nutr | 16 adults, half older and half younger | Glycine with cysteine | 2 weeks | Red blood cell glutathione, oxidative stress markers | Older adults' glutathione rose by about 95% |
| Kumar 2023, J Gerontol A | 24 adults aged 61 to 80 (randomized), plus 12 young adults | 100 mg/kg glycine plus 100 mg/kg NAC, or alanine placebo | 16 weeks | Glutathione, oxidative stress, gait speed, grip strength | Red cell glutathione up 225%; gait speed and grip strength rose; described as safe and well tolerated |
| Soh 2024, GeroScience review | 18 studies in healthy adults, 34 in people with health conditions | Varied | Up to 14 days (healthy); up to 4 months | Effects across 11 body systems | Most positive effects in the nervous system; healthy-adult sleep studies were small |
Lab and animal research: in rats, oral glycine did not change plasma melatonin (Bannai 2012), and, acting on NMDA receptors in the suprachiasmatic nucleus, raised skin blood flow, lowered core temperature and lengthened non-REM sleep (Kawai 2015). These pathways were not measured in people.
Studied Amounts by Setting
Amounts from research and regulations, not directions. Follow your product's label.
| Setting | Amount |
|---|---|
| Sleep studies | 3 g, taken before bed |
| GlyNAC trial in older adults | 100 mg per kg a day with the same amount of NAC; about 7 g of glycine at 70 kg, by our arithmetic |
| Supervised psychiatric research | 30 g a day for 12 weeks; 60 g a day for 8 weeks |
| Made by the body | About 3 g a day |
| Typical diet | 1.5 to 3 g a day |
| Food additive limit | Up to 0.2% of a finished beverage |
Benefits by goal, with dosing context, are covered in Glycine Benefits: What This Amino Acid Does, Dosage and Food Sources.
Safety, Interactions and Who Should Ask First
Glycine is part of the protein in everyday food. In a 12 week trial in people taking clozapine, 30 g a day was well tolerated, with no adverse changes in blood counts or blood chemistry (Potkin 1999). The 16 week GlyNAC trial described its regimen as safe and well tolerated (Kumar 2023).
| Medicine or situation | What is reported |
|---|---|
| Clozapine | In two placebo-controlled trials in adults with schizophrenia on clozapine, added glycine was given at 30 g and 60 g a day, and the authors suggested glycine may interfere with clozapine's effect (Potkin 1999, Evins 2000). Do not combine without the prescriber. |
| Other prescription medicines | Ask your clinician first. Our sleep powder's label also flags blood thinners. |
| Pregnancy, nursing, under 18 | Our sleep powder is not for these groups. |
| Driving and alcohol | Our sleep powder may cause drowsiness; do not drive or use machinery after it, and do not combine it with alcohol. |
| Plant allergies | Our sleep powder contains chamomile-derived apigenin; avoid it with an allergy to daisies, marigolds, chrysanthemums, ragweed or chamomile. |
Regulatory Status in the US
Under the Dietary Supplement Health and Education Act of 1994 (DSHEA), amino acids are dietary ingredients, so glycine is sold in supplements. FDA does not approve supplements before they are marketed; the maker is responsible for safety and labeling, and structure and function statements carry the disclaimer at the bottom of this page.
In conventional foods, glycine is an approved food additive under 21 CFR 172.812 for two technological uses: masking the bitter aftertaste of saccharin in beverages, at no more than 0.2% of the finished drink, and stabilizing mono- and diglycerides, at no more than 0.02%. It must meet Food Chemicals Codex specifications.
Glycine FAQ
What is the chemical formula of glycine?
C2H5NO2, written out as NH2CH2COOH, with a molecular weight of about 75.07 g/mol. It is also called aminoacetic acid, and its CAS number is 56-40-6.
Why does glycine have no L or D form?
Its side chain is a single hydrogen, so its central carbon holds two identical hydrogens and is not a chiral center. Every other amino acid used in protein has L and D forms.
How much glycine does the body make each day?
A 2009 analysis estimated about 3 g a day, mostly from serine, alongside 1.5 to 3 g a day from food. The authors argued total needs, including collagen, may be higher than that supply.
How is glycine regulated in US foods?
It is an approved food additive under 21 CFR 172.812, limited to masking saccharin's aftertaste in beverages at up to 0.2 percent and stabilizing mono- and diglycerides. In supplements it is a dietary ingredient under DSHEA.
What amounts of glycine have human studies used?
3 g before bed in sleep studies, 100 mg per kg a day together with NAC in a 16 week trial in older adults, and 30 to 60 g a day in supervised psychiatric research. These are study amounts, not directions.
Does glycine interact with any medicines?
Two trials suggested added glycine may interfere with the effect of clozapine. Anyone taking clozapine or other prescription medicine should ask their clinician first.
More on Glycine
Our guides
Related ingredients
Sources
- NIST Chemistry WebBook. Glycine. webbook.nist.gov
- MedlinePlus. Amino acids. Reviewed January 21, 2025. medlineplus.gov
- Meléndez-Hevia E, et al. A weak link in metabolism: the metabolic capacity for glycine biosynthesis does not satisfy the need for collagen synthesis. J Biosci, 2009. DOI 10.1007/s12038-009-0100-9
- NIH Office of Dietary Supplements. Dietary Supplements for Exercise and Athletic Performance: Fact Sheet for Health Professionals. ods.od.nih.gov
- Inagawa K, et al. Subjective effects of glycine ingestion before bedtime on sleep quality. Sleep Biol Rhythms, 2006. link.springer.com
- Yamadera W, et al. Glycine ingestion improves subjective sleep quality in human volunteers, correlating with polysomnographic changes. Sleep Biol Rhythms, 2007. link.springer.com
- Bannai M, et al. The effects of glycine on subjective daytime performance in partially sleep-restricted healthy volunteers. Front Neurol, 2012. PubMed 22529837
- Kawai N, et al. The sleep-promoting and hypothermic effects of glycine are mediated by NMDA receptors in the suprachiasmatic nucleus. Neuropsychopharmacology, 2015. PubMed 25533534
- Sekhar RV, et al. Deficient synthesis of glutathione underlies oxidative stress in aging and can be corrected by dietary cysteine and glycine supplementation. Am J Clin Nutr, 2011. PubMed 21795440
- Kumar P, et al. Supplementing glycine and N-acetylcysteine (GlyNAC) in older adults improves glutathione deficiency, oxidative stress, mitochondrial dysfunction, inflammation, physical function, and aging hallmarks: a randomized clinical trial. J Gerontol A Biol Sci Med Sci, 2023. PubMed 35975308
- Soh J, et al. The effect of glycine administration on the characteristics of physiological systems in human adults: a systematic review. GeroScience, 2024. PubMed 37851316
- Potkin SG, et al. Effect of clozapine and adjunctive high-dose glycine in treatment-resistant schizophrenia. Am J Psychiatry, 1999. DOI 10.1176/ajp.156.1.145
- Evins AE, et al. Placebo-controlled trial of glycine added to clozapine in schizophrenia. Am J Psychiatry, 2000. PubMed 10784481
- Electronic Code of Federal Regulations. 21 CFR 172.812, Glycine. ecfr.gov
- US Food and Drug Administration. Questions and Answers on Dietary Supplements. fda.gov
These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. Ask your clinician before starting glycine if you are pregnant or nursing, are under 18, take clozapine or any prescription medicine, or manage a health condition.