Glycine Supplements: What It Is, If It Works & What to Buy
Educational overview — not medical advice. Glycine is well tolerated, but if you take clozapine, ask your prescriber first (glycine may reduce its effect).
Glycine is the simplest amino acid — a building block for collagen, glutathione, and creatine, and a calming neurotransmitter. People take it mostly for sleep (~3 g before bed), where the evidence is real but modest. Two things to know before buying: it's one identical molecule, yet a 3 g dose costs ~12x more from some brands than others ($0.10 vs $1.17); and if you take magnesium glycinate or collagen, you're already getting glycine.
As an Amazon Associate we earn from qualifying purchases. Ranked by verified cost per gram, never commissions.
Start here
The chart that explains the category
Glycine is one molecule, identical across brands. Yet the cost of the same 3 g dose swings wildly — and powder beats capsules every time:
| Item | Value |
|---|---|
| BulkSupplements | $0.10 |
| NOW powder | $0.12 |
| Nutricost | $0.14 |
| NOW capsule | $0.35 |
| Double Wood | $0.40 |
| NutraBio | $0.40 |
| Thorne | $0.74 |
| Pure Encapsulations | $1.17 |
What glycine is
Glycine is the smallest amino acid and is classed as conditionally essential — your body synthesizes it, but under some conditions may not make enough (Wang 2013). It's a structural building block for collagen (about a third of it), the antioxidant glutathione, creatine, and heme, and it acts as an inhibitory (calming) neurotransmitter. Some researchers argue the body's own glycine production may fall short of the demand for collagen synthesis (Meléndez-Hevia 2009) — a hypothesis, not a proven population-wide deficiency.
Does it work? (the short version)
Its best-supported wellness use is sleep: 3 g before bed modestly reduced next-day fatigue in the best PubMed-indexed trial (Bannai 2012) — real, but not the insomnia cure marketing implies (the classic "better sleep quality" studies aren't PubMed-indexed). Its collagen and glutathione roles are genuine biochemistry but thin on human outcomes, and metabolic/blood-sugar claims are association, not treatment. Full breakdown on does glycine work.
The buying problem: a 12x price trap
Because glycine is identical across brands, the only thing to get right is not overpaying. The cost of a 3 g dose runs from about BulkSupplements's $0.10 to Pure Encapsulations's $1.17 — a ~12x gap for the same molecule, which an independent 2025 ConsumerLab test also found (9¢ to over $1.00 per 3 g). Powder is far cheaper than capsules. See the full cost ranking.
You may already be taking glycine
Before you buy a dedicated supplement: magnesium glycinate is ~86% glycine (about 1.2–1.3 g rides along with a 200 mg magnesium dose), and collagen is ~⅓ glycine (~2–3 g per scoop). Neither lists the glycine, but if you take either, you may not need a separate glycine at all. The full breakdown: glycine vs magnesium glycinate vs collagen.
Frequently asked questions
What is glycine and what does it do?
The simplest amino acid, conditionally essential. A building block for collagen (~⅓), glutathione, creatine, and heme, and a calming neurotransmitter. Taken mostly for sleep at ~3 g before bed.
Is glycine worth taking?
Cheap, very safe, worth a low-risk try for sleep — but modest, not a miracle. Collagen/glutathione roles are real biochemistry, not proven outcomes; metabolic claims are association. If you take magnesium glycinate or collagen, you may already get enough.
Which glycine supplement should I buy?
The cheapest verified one — it's an identical molecule and price isn't a quality signal (a 3 g dose ranges ~12x). Powder beats capsules on cost; buy a certified capsule only if you specifically want that.
Related guides
- Magnesium — magnesium glycinate is a big hidden glycine source; here's the magnesium side
- Collagen — ~⅓ glycine; what the evidence really shows
- Melatonin — the other popular sleep supplement, compared honestly
Sources
- Bannai M, et al. "The effects of glycine on subjective daytime performance in partially sleep-restricted healthy volunteers." Front Neurol. 2012. PMID: 22529837
- Wang W, et al. "Glycine metabolism in animals and humans." Amino Acids. 2013. PMID: 23615880
- Meléndez-Hevia E, et al. "A weak link in metabolism: the metabolic capacity for glycine biosynthesis does not satisfy the need for collagen synthesis." J Biosci. 2009. PMID: 20093739
- ConsumerLab. "Best Glycine Supplements." 2025. consumerlab.com
- Full product dataset: /glycine/cost-by-brand.json (CC BY 4.0).