BulkSupplements Glycine Powder Review

One scoop. BulkSupplements portions glycine at 3 g per serving, which is exactly the dose used across the human sleep studies (Yamadera 2007; Bannai 2012, PMID 22529837). Stir it into a small glass of water or warm — not hot — tea 30 to 60 minutes before bed. Because glycine is naturally sweet, it dissolves clear and tastes faintly sweet with no flavoring needed. There is no evidence that more than 3 g helps sleep, so there is no reason to heap the scoop.

It is 100% plain, unflavored glycine — no fillers, no anti-caking agents, no blend. That matters because the sleep evidence is specifically for glycine by itself; anything labeled 'glycine complex,' NAC+glycine, or magnesium glycinate is a different product with different evidence and was disqualified from this ranking. Plain free-form glycine is exactly what the studies used, and it is what you want for the 3 g pre-bed dose.

BulkSupplements runs per-batch, multi-stage third-party testing and manufactures in a cGMP facility. For a commodity amino acid like glycine, that verification is the main thing separating a trustworthy powder from an anonymous one — the glycine molecule is identical everywhere, so the value is in confirming purity and the absence of contaminants. It is not a boutique certification like NSF Certified for Sport, but the per-batch testing is exactly what you want for a bulk ingredient.

Genuinely cheaper. Glycine is one of the cheapest amino acids that exists, and a 1 kg bag yields roughly 330 servings of 3 g — enough for close to a year at one dose a night — which lands the cost per dose at a few cents, the lowest in the category. Capsules cost several times more per gram for the shell and the convenience. If you are willing to scoop a powder, this is the most cost-efficient way to take glycine for sleep, full stop.

1. [1] Bannai 2012 PMID 22529837 — The effects of glycine on subjective daytime performance in partially sleep-restricted healthy volunteers. In healthy volunteers whose sleep was restricted for three nights, 3 g of glycine before bed significantly reduced subjective daytime fatigue and sleepiness and improved reaction-time performance versus placebo. The best-replicated glycine sleep finding — but a small study, and the authors are affiliated with a glycine manufacturer (noted for transparency).
2. [2] Kawai 2015 PMID 25533534 — The sleep-promoting and hypothermic effects of glycine are mediated by NMDA receptors in the suprachiasmatic nucleus. Mechanistic study in rats: oral glycine promoted sleep and lowered core body temperature by acting on NMDA receptors in the suprachiasmatic nucleus (the master circadian clock), increasing skin blood flow and heat loss. Provides the leading biological explanation for glycine's sleep effect — but it is an animal study, so extrapolation to humans is indirect.
3. [3] Yamadera 2007 — Glycine ingestion improves subjective sleep quality in human volunteers, correlating with polysomnographic changes. In volunteers with unsatisfactory sleep, 3 g of glycine before bed improved subjective sleep quality and, on polysomnography, shortened latency to sleep onset and to slow-wave sleep. The canonical human glycine-sleep study and the source of the 3 g dose — but small (~11 subjects) and published in a journal PubMed does not index, so no PMID exists. Cited honestly without a fabricated identifier.