Solgar is a trustworthy, heritage brand and the glycine itself is clean free-form L-glycine — non-GMO, vegan and kosher, with the company's long-standing Gold Standard QC behind it. This is not a quality knock: the purity and quality of the glycine are not in question, and for a buyer who specifically wants Solgar at a smaller daily amount it is perfectly good. It ranks last purely on fit for the sleep use case. At 500 mg per capsule, hitting the studied 3 g dose means six capsules every night, and a 100-count bottle disappears in roughly two weeks at that rate — which makes it both inconvenient and expensive per dose for this specific job. If you want Solgar and use glycine at 500 mg to 1 g, it is a fine choice. For the 3 g sleep dose, a powder (#1 to #3) or a 1 g capsule (#4, #6) is the better tool. Here is the full breakdown.
Check on AmazonAffiliate link — Super Achiever Club earns a small commission at no extra cost to you.
Read the complete Glycine guide →Plain free-form L-glycine — non-GMO, vegan and kosher, no blend. Clean and exactly the glycine the sleep studies used; the ingredient scores level with the better capsules on purity. Nothing about the glycine itself is in question anywhere in this pick's ranking — the drawbacks are all about dose fit.
Solgar's long-standing Gold Standard QC reputation is a genuine strength — a heritage brand with decades of trust behind it. It scores below Thorne's third-party certification and Pure Encapsulations' clinician-grade tier, but comfortably in the trustworthy range for a commodity ingredient.
The worst on the list for the sleep dose. At 500 mg per capsule, the studied 3 g dose is six capsules a night — tied for the most of any pick. The glycine amount is fine; it is the swallow burden that is heavily penalized. A 1 g cap (Thorne, Double Wood) halves the count, and a scooped powder eliminates it.
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.
Among the highest cost per 3 g dose on the list. A 100-count bottle plus six caps per dose means it empties in roughly 16 nights at the full sleep dose, so you reorder constantly and the effective cost per dose is high. Premium-brand pricing on a 500 mg cap is simply the wrong economics for the 3 g sleep target.
“Plain free-form L-glycine, 500 mg per capsule.”
The listing states 500 mg of free-form glycine per capsule. This is the plain glycine this ranking requires, and the 500 mg cap is the honest reason the studied 3 g sleep dose is six capsules a night — the claim holds as stated.
“Non-GMO, vegan and kosher, with Solgar's Gold Standard QC.”
The product overview states a non-GMO, vegan, kosher formula, and Solgar's Gold Standard QC reputation is well documented. Appropriate, credible verification for a commodity amino acid from a heritage brand — the claim is accurate.
“100 vegetable capsules per bottle.”
The listing lists 100 vegetable capsules. At the studied 3 g sleep dose (six caps), that is only about 16 nights — the arithmetic behind the review's value and supply concerns. Accurate.
“Supports glycine's role in sleep and relaxation.”
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; note the label's own suggested use is a smaller daily amount than the 3 g sleep dose.
The most important thing to say up front is that this is not a quality knock. Solgar's free-form L-glycine is clean, non-GMO, vegan and kosher, from a heritage brand with a Gold Standard QC reputation. The problem is purely one of fit: the capsule is 500 mg, so the studied 3 g sleep dose is six capsules a night — tied for the most of any pick. For someone using glycine at the label's smaller daily amount, that is fine; for the 3 g sleep target specifically, it is the wrong tool.
Six capsules per dose against a 100-count bottle means Solgar empties in roughly 16 nights at the full 3 g sleep dose. That is the shortest run of any pick, so you reorder constantly, and the effective cost per dose climbs to among the highest on the list. Premium-brand pricing on a small-dose capsule is simply the wrong economics for a supplement you take nightly at 3 g — which is exactly why it lands at #8 despite clean glycine and a trusted name.
If you want the 3 g sleep dose, almost anything on this list serves it better: a scooped powder (#1 to #3) gives you the dose in one scoop at a fraction of the cost, and a 1 g capsule (Thorne #4, Double Wood #6) halves the count to three caps. Solgar makes sense only if you are a brand loyalist using glycine at a smaller daily amount. For the studied sleep dose, choose a powder or a 1 g cap instead.
The dose-fit issues aside, this 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). If you do take six caps nightly, give it one to two weeks before judging and stack it with a cool room and consistent sleep timing. Glycine is a small, well-tolerated edge, not a cure — and for that edge, a better-fitting product will serve you at the 3 g dose.
Solgar Glycine 500 mg is a trustworthy, heritage-brand product and the glycine itself is clean free-form L-glycine — non-GMO, vegan and kosher, with Gold Standard QC behind it. That is worth stating plainly: this is not a quality knock, and for a buyer using glycine at the label's smaller daily amount it is perfectly good. It ranks last purely on fit for the sleep use case. At 500 mg per capsule, the studied 3 g dose means six capsules every night, and a 100-count bottle disappears in roughly two weeks at that rate — inconvenient and expensive per dose for this specific job. If you specifically want Solgar and take glycine at 500 mg to 1 g, it is a fine choice. For the 3 g sleep dose, a powder (#1 to #3) or a 1 g capsule (Thorne #4, Double Wood #6) is the better tool. If you do use it at 3 g, take 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 Solgar · plain free-form glycine · 500 mg per capsule · 100 veg caps on AmazonThe overall winner — the studied 3 g dose in one scoop at the lowest cost per gram, per-batch tested. The better tool for the sleep dose if you will mix a powder.
See it on the list →The best-tested capsule, at 1 g per cap so the 3 g dose is three caps not six. Choose it if you want capsules but a lower count and top testing.
See it on the list →The value capsule — 1,000 mg per cap, 300 per bottle (about 100 nights), third-party tested. The better-fitting, cheaper capsule than Solgar for the 3 g sleep dose.
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.
