Rankings / Sleep & Recovery

Glycine

Sleep & Recovery · Amino acid / NMDA co-agonist

Tier B-

Reviewed by Read Off Label · Last reviewed · How we grade

nmda-modulatorthermoregulationotc
6.2 / 10
Tier B-
Ev 4.5 Bn 3.5 Sf 9

Bottom line

Read Off Label grades Glycine as B- (6.2/10) based on weak-moderate evidence, low-moderate benefit magnitude, and a low-risk safety profile.

Ajinomoto-era Japanese research tradition demonstrated modest but consistent subjective and polysomnographic sleep quality improvements at 3 g (faster sleep onset; improved sleep efficiency; reduced next-day fatigue).

Studied, labeled, or reported-use context: 3 g PO 30-60 min before bed — OTC; not individualized guidance.

If you were testing this on yourself

Two properties decide whether an n-of-1 experiment is readable and recoverable. These describe the experiment — they are not a judgment about whether to run it, and nothing here is a recommendation.

Can you undo it?

Reverses on stopping

An amino acid at food-adjacent doses; fully reversible with no withdrawal.

Can you tell if it worked?

Readable — Same night, if it works at all

Subjective sleep quality and sleep-onset latency.

What would fool you Sleep is the noisiest endpoint people try to self-measure. Several weeks of tracking either side is the minimum, and expectancy effects on subjective sleep quality are large.

What the evidence says

Ajinomoto-era Japanese research tradition demonstrated modest but consistent subjective and polysomnographic sleep quality improvements at 3 g (faster sleep onset; improved sleep efficiency; reduced next-day fatigue). Razak 2023 systematic review (GeroScience) covered 11 physiological systems and found nervous-system endpoints had the strongest evidence overall but flagged small samples and bias risk. Hannan 2024 Nutrients update review (PMID 39453231) re-confirmed sleep/recovery role. Cheap; sweet taste makes it easy to take; no tolerance documented. Distinct use case from the new Longevity entry (higher daily doses to address age-related shortfall) and from GlyNAC (paired with NAC for glutathione).

Mechanism

Simple amino acid; NMDA receptor co-agonist; inhibitory at spinal cord via strychnine-sensitive glycine receptors; reduces core body temperature via peripheral vasodilation aiding sleep onset; modest sleep quality improvement in Japanese RCTs

Studied, labeled, or reported dose & route

3 g PO 30-60 min before bed

This records doses and routes described in studies, approved labeling, clinical practice, or documented use. It is not individualized guidance and does not establish safety; context changes with indication, formulation, health history, monitoring, and other medicines.

Citations

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Common questions

What does the evidence show about Glycine's effects?
Read Off Label rates the evidence for Glycine as Weak-Moderate and the benefit magnitude as low-moderate, producing an overall grade of B- (6.2/10). Ajinomoto-era Japanese research tradition demonstrated modest but consistent subjective and polysomnographic sleep quality improvements at 3 g (faster sleep onset; improved sleep efficiency; reduced next-day fatigue).
What safety findings are reported for Glycine?
Glycine has a low risk profile in the database. Low (very well-tolerated; sweet taste; rare GI upset at high doses) Legal status: OTC.
What doses or routes are reported for Glycine?
3 g PO 30-60 min before bed This is context from studies, approved labeling, clinical practice, or documented use; it is not individualized guidance and does not establish safety.
How does Glycine work?
Simple amino acid; NMDA receptor co-agonist; inhibitory at spinal cord via strychnine-sensitive glycine receptors; reduces core body temperature via peripheral vasodilation aiding sleep onset; modest sleep quality improvement in Japanese RCTs

This is an independent synthesis of published research by a non-clinician. Scores are opinions supported by citations, not prescriptions. See the full disclaimer and methodology for how this score was produced and what it does and doesn't mean.