If you have decided on capsules and value is your priority, Double Wood Glycine is the answer. Each two-capsule serving delivers 1,000 mg (500 mg per cap), so the studied 3 g dose is six caps; the 300-count bottle lasts about 50 nights at the full dose, and the per-gram cost is the lowest of any capsule on the list. The glycine is plain, non-GMO and gluten-free, and third-party tested. What you give up is a little of the elite testing pedigree you would get from Thorne or Pure Encapsulations — Double Wood's testing is solid and transparent, but it is not third-party certified or clinician-grade. That is the trade for the lower price, and it is a fair one for most buyers. It is worth being clear that a powder is still cheaper per gram if you are willing to mix it; Double Wood's whole pitch is being the cheapest way to get capsule convenience. Here is the full breakdown.
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Read the complete Glycine guide →Plain free-form glycine, non-GMO and gluten-free, no blend — the glycine the sleep studies used. Nothing disqualifying. It scores a touch below the clinician-grade capsules (Thorne, Pure Encapsulations) on label discipline and excipient transparency, but for a value capsule the purity is genuinely good.
Third-party tested with a non-GMO, gluten-free formula — solid and transparent, and ahead of budget capsules that state only in-house checks. The reason it scores below the top is that it lacks Thorne's third-party certification and Pure Encapsulations' clinician-grade hypoallergenic pedigree. For plain glycine at this price, the verification is trustworthy.
Weaker than the label reads at first glance: the 1,000 mg is per two-capsule serving, so at 500 mg per capsule the studied 3 g dose is six caps a night — twice the count of Thorne's 1 g capsules and the same swallow burden as Pure Encapsulations and Solgar. The dose is still precise and easy to hit, and the 300-count bottle keeps reorders rare, but six capsules versus a single 3 g scoop or a three-cap dose is a real convenience drawback.
Scored neutral, as capsules are throughout this ranking. A capsule avoids taste entirely — good for people who do not want to mix — but forfeits glycine's naturally sweet, pleasant-in-water quality, a genuine upside of the powders. A different trade, not a better or worse one.
The best value among capsules by a clear margin: the cheapest capsule cost per gram on the list, and a 300-count bottle that covers about 50 nights at the full 3 g dose. It cannot beat a bulk powder on cost per gram — nothing capsuled can — but among capsules this is decisively the value pick.
“1,000 mg of plain glycine per two-capsule serving.”
The listing states 1,000 mg of glycine per serving, with a serving being two vegetarian capsules — 500 mg per capsule. This is the plain free-form glycine this ranking requires; the honest consequence is that the studied 3 g dose is six capsules, not three. The per-serving claim holds as stated.
“300 capsules per bottle — about 50 nights at the full dose.”
The listing lists 300 capsules (150 two-capsule servings). At the studied 3 g dose (six caps), that is about 50 nights — still a solid supply, and part of what makes the per-gram cost the lowest of any capsule here. Accurate.
“Third-party tested, non-GMO and gluten-free.”
The listing states third-party testing and a non-GMO, gluten-free formula. Solid, transparent verification for a value capsule — ahead of in-house-only budget brands, though below Thorne's certification tier. The claim is accurate.
“Supports relaxation and 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.
Double Wood wins the budget-capsule slot on price, not capsule count: 500 mg per capsule (1,000 mg per two-capsule serving) and 300 capsules per bottle. The studied 3 g dose is six caps — the same burden as Pure Encapsulations and Solgar, and twice Thorne's three — but the 300-count bottle still covers about 50 nights at that dose and delivers the lowest capsule cost per gram on the list. If you want capsule convenience without paying a premium, this is the math that makes it the pick.
Double Wood states third-party testing and a non-GMO, gluten-free formula, which is genuinely solid and transparent — clearly ahead of budget capsules that claim only in-house checks. What it does not carry is Thorne's third-party certification or Pure Encapsulations' clinician-grade hypoallergenic pedigree. That gap is exactly the trade you make for the lower price, and for plain, tested glycine it is a reasonable one; if maximum verification is your bar, Thorne (#4) is the pick.
It is worth stating plainly: the glycine in this capsule is chemically identical to the bulk powders, and a powder (#1 to #3) is still cheaper per gram and lets you take one 3 g scoop. Double Wood's entire pitch is being the cheapest way to get capsule convenience — no scooping, no mixing, six caps and done. If you have decided you want capsules, it is the value answer; if cost per gram is what you care about, a powder wins outright.
The value capsule 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 the six-cap 3 g dose nightly for one to two weeks before judging, and stack it with a cool room and consistent sleep timing. This is the best-value capsule way to take glycine for sleep — it is still a small, well-tolerated edge, not a cure.
Double Wood Glycine is the pick if you have decided on capsules and value is your priority. The 1,000 mg two-capsule serving means the studied 3 g dose is six caps, the 300-count bottle lasts about 50 nights, and the per-gram cost is the lowest of any capsule on the list. The glycine is plain, non-GMO and gluten-free, and third-party tested. You give up a little of the elite testing pedigree you would get from Thorne (third-party certified) or Pure Encapsulations (clinician-grade hypoallergenic), and you accept six capsules a night where Thorne needs three — that is the trade for the lower price, and a fair one for most buyers. And it is honest to note that a powder is still cheaper per gram if you will mix it; this product is the cheapest way to get capsule convenience, not the cheapest glycine overall. As with every pick, take 3 g (six caps), 30 to 60 minutes before bed, give it one to two weeks, and stack it with good sleep timing and a cool room.
Check Double Wood · plain glycine capsules · 1,000 mg per 2-cap serving (500 mg per capsule) · 300 caps on AmazonThe best-tested capsule, third-party certified, with 1 g caps — so the 3 g dose is three capsules instead of Double Wood's six. Choose it over Double Wood if verification pedigree and fewer capsules matter more than the lowest capsule price.
See it on the list →The overall winner — plain glycine at the lowest cost per gram with a 3 g scoop. Buy it if cost per gram matters more than capsule convenience.
See it on the list →The cleanest allergen-free capsule label for sensitive users — the same 500 mg caps and six-capsule dose as Double Wood. Choose it if hypoallergenic purity outranks price.
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.
