Amino Acid
Glycine
Also known as: Gly
Simplest amino acid with diverse roles in collagen synthesis, sleep quality, neurotransmission, and detoxification.
Last reviewed June 2026 · Evidence graded from peer-reviewed research, not editorial opinion. Educational only — not medical advice.
Every Glycine product we have scored
| # | Product | Score | Per serving |
|---|---|---|---|
| 1 | Nutricost Glycine Powder | 92 A | $0.17 |
| 2 | Thorne Glycine | 92 A | $0.25 |
| 3 | Pure Encapsulations Glycine | 92 A | $0.58 |
| 4 | Life Extension Glycine | 92 A | $0.13 |
| 5 | NutraBio Glycine Powder | 92 A | $0.13 |
| 6 | Pure Encapsulations NAC + Glycine powder | 88 A | $1.27 |
| 7 | Pure Encapsulations Pure Tranquility Liquid | 87 A | $1.76 |
| 8 | Life Extension Optimized Carnitine | 87 A | $0.78 |
| 9 | Thorne MediClear-SGS™ - Vanilla | 86 A- | $2.10 |
| 10 | Vital Nutrients Glycine Powder | 85 A- | $0.60 |
| 11 | NOW Foods Double Strength 5-HTP | 84 A- | $0.37 |
| 12 | Swanson GABAplex with L-Tyrosine & L-Theanine | 84 A- | $0.28 |
Scored on dose accuracy, form, label transparency and third-party testing. Per-serving cost is list price divided by servings per container. No brand pays to be listed or ranked.
Common questions
How much Glycine should I take?
The typical range is 3-5 g before bed for sleep; up to 10-15g for other uses. Safe long-term
When should I take Glycine?
Before bed for sleep. Optional.
Which form of Glycine is best?
Powder — Sweet taste, easy to use. Other forms in the catalog: Capsules.
Is Glycine safe?
Commonly reported: Mild sedation, GI upset at high doses. Serious warnings: None. May support liver
Which Glycine supplement scores highest?
Nutricost Glycine Powder, at 92/100. Scored on dose accuracy, form, label transparency and third-party testing — no brand pays to be listed or ranked.
Daily target & upper limit
3 g / dayGlycine has an established daily reference intake. See best forms, label synonyms, upper-limit warnings, and top-scoring supplements:
Glycine dosage reference →Primary uses
- Sleep quality
- Collagen synthesis
- Detoxification
- Neuroprotection
What systematic reviews concluded
Outcomes that systematic reviews of Glycine reached a verdict on: 1 with a benefit, 1 with no effect, 1 unclear. Each is quoted from a review and linked to it on PubMed. How these were read.
Reviews found a benefit (1)
“including improved psychiatric symptoms from longer-term glycine administration in psychiatric populations” PMID 37851316
Reviews found no effect (1)
“The results of the analysis showed that neither stool output nor duration of diarrhoea was reduced by the experimental formulations.” PMID 1835674
Not enough to say: sleep.
1 finding from reviews in specific patient groups (such as cancer, pregnancy or surgery) is not shown here.
How it works
- Inhibitory neurotransmitter
- Precursor to glutathione
- 1/3 of collagen amino acids
- Lowers core body temperature
Dosage
- Typical range
- 3-5 g before bed for sleep; up to 10-15g for other uses
- Timing
- Before bed for sleep
- With food
- Optional
- Duration
- Safe long-term
- Special populations
- Poor sleepers, detox support
Forms
- Powder
- Capsules
Safety
Common side effects
- Mild sedation
- GI upset at high doses
Contraindications
- None
Products containing Glycine
Top-scoring supplements in our catalog that list Glycine on the label. Each product is graded on Formulate's ingredient-level rubric — dose accuracy, form, transparency, and third-party testing.
Known interactions
Evidence notes
Growing evidence for sleep and health
Grade B: Some human trials support key claims; further confirmation needed.
Cited research for Glycine
Clinical studies referenced across Formulate guides that mention glycine. Each links to the full study page with PubMed source + the guides that cite it.
- Kawai N, Sakai N, Okuro M, et al. (2015)Neuropsychopharmacology
The sleep-promoting and hypothermic effects of glycine are mediated by NMDA receptors in the suprachiasmatic nucleus
- Bannai and Kawai (2012)Journal of Pharmacological Sciences
New therapeutic strategy for amino acid medicine: glycine improves the quality of sleep
- Yamadera W, Inagawa K, Chiba S, et al. (2007)Sleep and Biological Rhythms
Glycine ingestion improves subjective sleep quality in human volunteers
Glycine compared head-to-head
Related in Amino Acid
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Medical disclaimer. This page is educational and does not replace advice from a qualified healthcare provider. Individual needs and risks vary — consult a professional before starting, stopping, or combining supplements, especially if you are pregnant or nursing, taking medication, or managing a health condition.