Glycine — Stack & Timing
Educational timing and stacking information based on how Glycine has been studied. Not a prescription. Not medical advice.
This is educational information only, not medical advice. Supplement needs vary by individual, health status, and dietary patterns. Consult a healthcare provider before starting any supplement regimen, particularly if you take prescription medications.
Stack & Timing Guidance
Educational summary based on how Glycine has been studied and commonly used.
Commonly studied timing
For sleep support, glycine is most commonly used 30–60 minutes before bed, consistent with the human trial protocols. For collagen or metabolic support, taking it with meals alongside a collagen-containing protein source is a common approach. Morning or daytime use is not associated with drowsiness at typical doses.
Dose ranges used in studies
Human sleep studies have used 3 g/night. GlyNAC studies in older adults have used higher glycine doses (1.33 mg/kg/day, approximately 8–10 g for average adults) alongside equivalent NAC doses. Glycine powder is widely available, inexpensive, and has a mildly sweet taste. No established UL means there is flexibility in dose experimentation, but 3–5 g is the range with direct human evidence for sleep.
↑ These are ranges from research studies, not personal dosing recommendations. Discuss with a clinician.
Commonly paired with
Both have independent sleep evidence via different mechanisms — glycine via thermoregulation, magnesium via NMDA/GABA modulation. Often combined in evening sleep stacks.
Note: The combination is commonly used but has not been tested head-to-head in an RCT; each component has individual evidence.
Glycine + NAC together provide two of glutathione's three precursors. The GlyNAC combination has RCT evidence for improving glutathione levels and aging biomarkers in older adults.
Note: GlyNAC combination RCT evidence exists (Kumar et al., 2017; Sekhar group). Cannot yet isolate glycine's individual contribution.
Glycine is the most abundant amino acid in collagen. Supplementing glycine alongside collagen peptides may support collagen synthesis pathways; some joint and skin studies use collagen + vitamin C + glycine protocols.
Note: Combination rationale is mechanistic; direct RCT evidence for the combined stack is limited.
Safety & interactions
Glycine is widely considered one of the safest supplements available. No upper intake limit has been established by major health authorities. Mild GI discomfort is the most commonly noted side effect at higher doses. There is no evidence of dependency, tolerance, or rebound insomnia. Glycine is not a sedative and does not act on GABA-A receptors in the same way as benzodiazepines. It is not a substitute for treating underlying sleep disorders, mood conditions, or medical conditions.
- •Clozapine (antipsychotic): Glycine may reduce the efficacy of clozapine — avoid combining without medical supervision
- •Other antipsychotics: Theoretical interaction via glycine receptor modulation; consult prescriber if on antipsychotic medications
Individuals on clozapine or other antipsychotic medications should consult their prescribing physician before using glycine supplements. No other absolute contraindications are established at typical supplemental doses.