Glycine
Summary
Glycine is a non-essential amino acid. A small study gave 3 g at bedtime during sleep restriction and found less next-day fatigue. In type 2 diabetes, 5 g/day for 3 months lowered A1C and inflammatory markers versus placebo (grade D). Very high doses were studied only as an add-on in schizophrenia under medical supervision.
Key facts
- The simplest amino acid; made in the body and abundant in collagen and gelatin[4]
- 3 g at bedtime reduced next-day fatigue after three nights of restricted sleep in healthy volunteers[1]
- In rats, glycine acted on NMDA receptors in the brain clock area and lowered core body temperature[4]
- 2 graded human outcomes on this page
- October 11, 2026
How it works
ProposedGlycine is an inhibitory neurotransmitter in the spinal cord and a co-agonist at NMDA receptors. Rat studies suggest its sleep effect comes from NMDA receptors in the suprachiasmatic nucleus and a drop in core body temperature.[4]
What the human research says
Human trials only, one row per outcome. The form column shows what each trial actually tested. Grades follow our evidence-grading policy.
At a glance: strongest evidence per outcome
| Outcome | Grade | Effect | Strongest evidence | Rows |
|---|---|---|---|---|
| Blood sugar | Grade D | Improved | RCT · n = 74 · 2008 | 1 row |
| Psychiatric add-on | Grade D | Improved | Crossover RCT · n = 17 · 2004 | 1 row |
Every graded row
| Outcome | Effect | Grade | Best evidence | PMID |
|---|---|---|---|---|
| A1C and inflammatory markers in type 2 diabetes | Improved | Grade D | RCT · n = 74 · 2008 Adults with type 2 diabetes Form: Glycine powder · Dose: 5 g/day (in three doses) · Duration: 3 months A1C and TNF-receptor I fell more than with placebo, and interferon-gamma rose. | 18852529 (opens PubMed)Source [2] |
| Negative symptoms added to antipsychotics | Improved | Grade D | Crossover RCT · n = 17 · 2004 People with schizophrenia on olanzapine or risperidone Form: Glycine · Dose: 0.8 g/kg/day · Duration: 6 weeks per period Negative symptoms fell by about 23% versus placebo; glycine was well tolerated under supervision. | 14732596 (opens PubMed)Source [3] |
Forms
| Form | Elemental % | Absorption (human data) | GI tolerance | Studied for |
|---|---|---|---|---|
| Glycine powder or capsules | Varies | Water-soluble free amino acid; no head-to-head human absorption data between forms. | Well tolerated at 0.8 g/kg/day in a supervised 6-week trial.[3] | Sleep, blood-sugar and psychiatric add-on trials |
Studied doses
Doses studied in human trials ranged from 3 g at bedtime for three nights to 5 g/day for 3 months; psychiatric trials used 0.8 g/kg/day under medical supervision.[1][2][3]
Interactions
Published interactions only: each row cites a source. No row means none was found in our sources, not that a combination is safe.
Medicines
- ClozapineRCTGlycine-site agonists may not add benefit to clozapine, unlike other antipsychotics, according to the trial background.[3]
Who should be careful
- Psychiatric conditions
- High-dose glycine was tested only as a supervised add-on to antipsychotics; changes to psychiatric treatment belong with the prescriber.[3]
- Diabetes medicines
- Glycine lowered A1C in one trial, so blood-sugar effects could add to diabetes medicines.[2]
Talk to your pharmacist or clinician before starting a supplement, especially if you take prescription medicines.
Where to buy Glycine
Products from brands we partner with that contain Glycine. Listing a product is not a claim that it works; check the amount per serving against the doses studied above, and the label for other ingredients.
- SupersmartPaid linkGlycine PowderHalf scoop: 2.5 g pure glycine; 72 servings (180 g)Shop at Supersmart (opens in new tab)Price and label checked 2026-10-11 on the brand’s site.
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- Offer terms from Supersmart’s site and its affiliate program, checked Oct 8, 2026. Offers can change; the brand's checkout is final.
Frequently asked questions
Does glycine help sleep?
One small study found 3 g at bedtime reduced next-day fatigue after three nights of restricted sleep. Larger trials are lacking.[1]
Is glycine the same as GlyNAC?
No. GlyNAC is glycine combined with N-acetylcysteine; it has its own page and trials.
Is glycine safe?
Glycine was well tolerated even at 0.8 g/kg/day in a supervised 6-week trial, but that dose is far above supplement servings.[3]
Does glycine lower blood sugar?
One 3-month trial in type 2 diabetes found lower A1C with 5 g/day. It has not been confirmed in larger trials.[2]
Sources
- [1]The effects of glycine on subjective daytime performance in partially sleep-restricted healthy volunteers.. Front Neurol, 2012. RCT
- [2]Glycine treatment decreases proinflammatory cytokines and increases interferon-gamma in patients with type 2 diabetes.. J Endocrinol Invest, 2008. RCT
- [3]High-dose glycine added to olanzapine and risperidone for the treatment of schizophrenia.. Biol Psychiatry, 2004. crossover-RCT
- [4]The sleep-promoting and hypothermic effects of glycine are mediated by NMDA receptors in the suprachiasmatic nucleus.. Neuropsychopharmacology, 2015. animal-study
What changed
- Corrected the effect arrow (↑ improved, ↓ worsened for participants) on: A1C and inflammatory markers in type 2 diabetes.
- First draft. Every PMID checked against NCBI E-utilities (title, journal and year taken from the PubMed record) and each evidence row written from its PubMed abstract.