The cleanest allergen-free glycine label — for sensitive users, at a premium and six caps.
Pure Encapsulations Glycine is the pick for one specific buyer: someone who wants the cleanest, most allergen-free label possible and is willing to pay for it. The hypoallergenic formulation — free of common allergens and needless excipients — and the brand's clinician-grade, 30-plus-year QC reputation are genuinely best-in-class. If you react to fillers or simply want the most transparent, stripped-down glycine label on the shelf, this is built for you.
The catch is purely practical. At 500 mg per capsule, the studied 3 g sleep dose is six capsules a night — the most of any pick — and the cost per gram is among the highest on the list. Neither is a quality knock; the glycine and the label are excellent. They are simply why this sits at #5 rather than higher: for buyers who want plain glycine at a fair price with fewer capsules, a powder or a 1 g-capsule pick is the better tool. Here is the full breakdown.
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Among the cleanest labels in supplements: plain free-form glycine, hypoallergenic, free of common allergens and unnecessary excipients, vegan and gluten-free. Nothing disqualifying and nothing extraneous. This ties Thorne for the top purity score on the list — for chemically-sensitive users, it is the standout.
Clinician-grade QC from a brand with a 30-plus-year reputation, third-party verified. Just a hair below Thorne's certification-and-pro-team pedigree, but comfortably ahead of the powders and budget capsules. For a commodity ingredient, this is exactly the verification worth paying for — the label-purity story and the testing story reinforce each other here.
The practical weak point. At 500 mg per capsule (1,500 mg per 3-cap serving), the studied 3 g dose is six capsules a night — the most of any pick. The glycine amount itself is fine; it is the swallow burden that is penalized. If you want the studied dose in fewer capsules, a 1 g-cap pick (Thorne, Double Wood) halves the count.
Scored neutral, as capsules are throughout this ranking. A capsule avoids taste entirely — good for people who do not want to mix anything — but forfeits glycine's naturally sweet, pleasant-in-water quality, a real upside of the powders. A different trade, not a better or worse one.
The lowest value score on the list, by design. Premium clinician-grade pricing plus a 500 mg cap (six per dose) puts the cost per gram at the top of the category. You are paying for the hypoallergenic label and QC pedigree, not a better molecule. Fair for what it is — a label-purity pick — but decidedly not a value play.
“Hypoallergenic, free of common allergens and unnecessary excipients.”
The listing describes a hypoallergenic, vegan, gluten-free formula free of common allergens and needless excipients, consistent with Pure Encapsulations' clinician-grade positioning. This is the cleanest label on the list — the claim holds as stated.
“Plain free-form glycine, 500 mg per capsule (1,500 mg per 3-cap serving).”
The label lists 1,500 mg per 3-capsule serving, i.e. 500 mg per capsule of plain glycine. Accurate — and the honest reason the review flags that the studied 3 g sleep dose is six capsules a night.
“Clinician-grade, third-party verified quality.”
Pure Encapsulations' clinician-preferred reputation and third-party verification over a 30+ year history are well documented. Appropriate, real verification for a commodity amino acid — just below Thorne's certification tier, and the claim is accurate.
“Supports restful sleep at the glycine dose.”
Directionally supported by the human evidence on glycine — Yamadera 2007 and Bannai 2012 — but that evidence is moderate, drawn from a few small studies mostly from one lab, and describes glycine generally rather than this product. A reasonable category claim, not a proven product-specific outcome.
Pure Encapsulations exists for a specific buyer: someone who reacts to fillers, has allergen sensitivities, or simply wants the most transparent, stripped-down label available. On that axis it is best-in-class — hypoallergenic, free of common allergens and needless excipients, plain free-form glycine and little else. If that describes you, the premium is justified and the peace of mind is real. If it does not, you are paying for a purity feature you may not need.
At 500 mg per capsule, the studied 3 g dose is six capsules — the most of any pick on the list. The glycine amount is fine; it is the nightly swallow burden that is the drawback, and it is why this ranks below the 1 g-capsule picks despite a cleaner label. If you love the hypoallergenic formulation but want fewer capsules, there is no way around it here — Thorne (#4) or Double Wood (#6) at 1 g per cap cut the count to three, though neither matches this label's allergen discipline.
Glycine is chemically identical everywhere, so Pure Encapsulations' premium buys the hypoallergenic formulation and a clinician-grade QC pedigree — not a more potent molecule. That is a fair trade for sensitive users and clinician-directed buyers, but it means the cost per gram sits at the top of the category. For anyone whose priority is plain glycine at a fair price, a powder (#1 to #3) delivers the same active far cheaper.
The cleanest label still delivers just glycine: a gentle aid backed by moderate evidence from a few small studies. About 3 g before bed improved subjective sleep quality and shortened polysomnographic sleep latency (Yamadera 2007), and most reliably reduced next-day fatigue after a short night (Bannai 2012). Take six caps nightly for one to two weeks before judging, and stack it with a cool room and consistent sleep timing. This is the cleanest-label way to take glycine for sleep — it is still a small, well-tolerated edge, not a cure.
Pure Encapsulations Glycine is the right call for a narrow, well-defined buyer: someone with allergen sensitivities or a strong preference for the most transparent, stripped-down label available. On that axis it is best-in-class — hypoallergenic, free of common allergens and needless excipients, from a clinician-preferred brand with a 30-plus-year QC reputation. The catch is purely practical, not a quality issue. At 500 mg per capsule the studied 3 g dose is six capsules a night, and the cost per gram is among the highest on the list. If the hypoallergenic label is worth that to you, it is genuinely worth it; if you just want plain glycine at a fair price with fewer capsules, a powder (#1 to #3) or a 1 g-capsule pick (Thorne #4, Double Wood #6) makes more sense. As with every glycine product, take 3 g, 30 to 60 minutes before bed, give it one to two weeks, and stack it with good sleep timing and a cool room.
The best-tested capsule, at 1 g per cap so the 3 g dose is three caps not six. Choose it over Pure Encapsulations if a low capsule count and top testing pedigree matter more than the hypoallergenic label.
See it on the list →The value capsule — 1,000 mg per cap, 300 per bottle, third-party tested, at the lowest capsule cost per gram. Choose it if you want capsules cheaply and do not need the clean-label premium.
See it on the list →The overall winner — plain glycine at the lowest cost per gram with a 3 g scoop. Buy it if a fair price and one pre-portioned dose matter more than a hypoallergenic capsule label.
See it on the list →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).
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.
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.
