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📰Read the full Glycine evidence review on GMJ News →Complete clinical article, references and updates on news.gmj.ge. This page is the structured safety summary.⚠ GlyNAC protocol: 1.2 g glycine + 600 mg NAC BID — reversed GSH deficiency and aging markers [2]
⚠ Sleep dose: 3 g before bedtime — unique temperature-lowering mechanism, no sedation [3]
⚠ Clozapine patient — glycine may reduce clozapine efficacy [1]
⚠ Not a substitute for collagen supplements (different mechanism) [1]
ℹ️ Not obtained from food. Obtained as part of dietary protein (and made by the body) rather than tracked toward a daily target.
🔬 Lab interpreter
Recommended test
No routine monitoring
No routine monitoring
Reference range / target
N/A
N/A
For GlyNAC protocol: GSH levels in research settings [2].
Full lab monitoring ↓⚕ For professionals — confirm ranges against your local laboratory.
Clinical verdict
Glycine is a triple-play: sleep (3 g before bed — lowers core temp without sedation), anti-aging (GlyNAC reversed aging hallmarks in RCT), and collagen synthesis (33% of collagen is glycine). The GlyNAC combination is one of the most promising aging interventions studied. Sweet taste, dissolves easily, inexpensive. Sleep mechanism is unique — no sedation [1] [2] [3].
1 How much do I need?
👤 Adults: Specific dosage data under clinical review
👴 Elderly: Specific dosage data under clinical review
🤰 Pregnancy: See guidance
Normal body constituent. Safe at dietary levels. No supplementation data [1].
👦 Pediatric: See guidance
Normal body constituent. No specific supplementation studies [1].
🏃 Athletes: Standard dose
⚖️ Obesity: Standard dose
Fat-soluble compounds may require dose adjustment in obesity.
🩺 Renal: Consult specialist
Dose adjustment may be needed in renal impairment.
🌱 Vegan: Standard dose
How to take
💊 With food: Dissolves in any beverage. Mildly sweet [1].
🚫 Avoid: With clozapine (may reduce efficacy) [1].
2 Which form?
| Form | Bioavailability | Vegan | Cost |
|---|---|---|---|
| ['Glycine powder', 'common', 'Pure amino acid. Mildly sweet taste. Dissolves easily. Inexpensive [1].'] | Standard | Check label | |
| ['Glycine capsules', '', '500–1,000 mg per capsule [1].'] | Standard | Check label | |
| ['GlyNAC combination', 'preferred', 'Glycine + NAC together. The form used in the aging RCT [2].'] | Standard | Check label |
3 Common questions
How does glycine improve sleep? ▼
Unlike benzodiazepines or melatonin, glycine improves sleep through peripheral vasodilation → core body temperature reduction — mimicking the natural pre-sleep temperature drop [3]. It does NOT cause sedation or drowsiness. 3 g before bedtime is the studied dose.
What is GlyNAC? ▼
Glycine + N-Acetylcysteine, the combination providing two of three glutathione precursors (cysteine from NAC + glycine). A 2021 RCT by Sekhar et al. showed GlyNAC reversed glutathione deficiency and multiple aging hallmarks in older adults [2]. This is one of the most promising aging interventions.
Is glycine the same as collagen? ▼
No — glycine is one amino acid; collagen is a protein containing ~33% glycine. Taking glycine supplements supports collagen synthesis but does not provide the specific collagen-derived signaling peptides that collagen supplements do [1].
Can glycine help schizophrenia? ▼
High-dose glycine (0.4–0.8 g/kg/day) acts as an NMDA receptor co-agonist and has improved negative symptoms in some schizophrenia trials. However, it may reduce clozapine efficacy. Used only under psychiatric supervision [1].
4 Clinical evidence
Strong
One-third of collagen is glycine — essential for collagen synthesis [1]. Inhibitory neurotransmitter at glycine receptors (brainstem, spinal cord) [1]. Glutathione precursor (glycine is one of three GSH amino acids) [1]. HIGH
Moderate
Sleep quality: 3 g before bedtime improved subjective sleep quality, reduced daytime sleepiness, and improved cognitive performance next day in RCTs — mechanism: peripheral vasodilation → core temperature drop [3]. GlyNAC for aging: RCT in older adults (n=24) showed GlyNAC supplementation corrected glutathione deficiency, reduced oxidative stress, improved mitochondrial function, inflammation, insulin resistance, and endothelial function [2]. Schizophrenia (adjunctive): high-dose glycine (0.4–0.8 g/kg/day) improved negative symptoms as NMDA co-agonist [1]. MODERATE
Insufficient
5 Safety, toxicity & adverse events
Relative
⚠ Concurrent clozapine — glycine can reduce clozapine efficacy (documented)
⚠ Pregnancy and lactation — supplement-level safety not established
🚩 Red flags
● Clozapine patient adding glycine — may reduce drug efficacy [1]
6 Interactions
Drug interactions
Clozapine Moderate
Mechanism: Glycine acts as NMDA co-agonist. May interfere with clozapine's complex receptor pharmacology. [1]
Effect: Potentially reduced clozapine efficacy for schizophrenia. [1]
Action: Avoid glycine supplementation in clozapine-treated patients [1].
Supplement synergies
NAC (GlyNAC protocol) · 600 mg NAC BID + 1.2 g glycine BID
Together they provide 2 of 3 glutathione precursors. The 2021 RCT combination [2].
Together they provide 2 of 3 glutathione precursors. The 2021 RCT combination [2].
Vitamin C · 500 mg vitamin C
Vitamin C is essential for collagen synthesis; glycine is the most abundant collagen amino acid [1].
Vitamin C is essential for collagen synthesis; glycine is the most abundant collagen amino acid [1].
Collagen Peptides · 5–10 g collagen
Glycine supplements + collagen peptides = comprehensive collagen support (amino acids + signaling peptides) [1].
Glycine supplements + collagen peptides = comprehensive collagen support (amino acids + signaling peptides) [1].
7 Regulatory
United States (FDA): GRAS. Dietary supplement [1].
European Union: Food supplement [1].
South Korea: Dietary supplement.
8 US supplement products
518
on-market products containing Glycine (NIH DSLD)
Brands carrying Glycine (170)
Click a brand to see its Glycine products.
9 Frequently paired with
10 Cite this page
Vancouver: Pkhakadze G. Glycine — safety profile [Internet]. Tbilisi: PHIG; 2026 [cited 2026 Aug 31]. Available from: https://supplement.ge/ingredients/glycine/
APA 7th: Pkhakadze, G. (2026). Glycine — Safety profile. Public Health Institute of Georgia. https://supplement.ge/ingredients/glycine/
📋 Editorial information
Author: Prof. G. Pkhakadze, MD, MPH, PhD
Institution: Public Health Institute of Georgia (PHIG)
Affiliation: David Tvildiani Medical University (DTMU)
First published: January 2026
Last reviewed: 2026-05-29
Next review: March 2027
References: 3 cited sources
COI: SupplementIndex receives no funding from supplement manufacturers. All content independently authored by PHIG.
Process: Systematic literature review
📄 License & reuse
Published under Creative Commons Attribution 4.0 International (CC BY 4.0). You may share and adapt for any purpose with attribution.
Pkhakadze G. "Glycine — Safety Profile." SupplementIndex, PHIG, 2026. https://supplement.ge/ingredients/glycine/ CC BY 4.0.
GP
Prof. G. Pkhakadze, MD, MPH, PhD
Professor of Public Health · Head of Department, DTMU
Editor-in-Chief, Georgian Medical Journal (ISSN 3088-4322)
Chair, Public Health Institute of Georgia · UEMS Public Health Section
Educational and public health purposes. CC BY 4.0. Consult your healthcare provider before starting any supplement. Corrections: info@accreditation.ge. Publisher: PHIG