Life Extension Glycine Review
#7 of 8 · Best premium-brand single cap✓ Label verified · Supplement Facts read Sep 7, 2026Real retailer photo, cut out. Label unedited.
Buy it. A good QC-brand 1 g glycine cap with a COA — but a small 33-night bottle drags the value. Plain, vegetarian, non-GMO glycine at 1,000 mg per capsule (so 3 g is three caps) from a QC-respected brand with a published Certificate of Analysis.
Mid-to-premium capsule pricing per gramHigher per 3 g dose (3 × 1 g caps, small bottle)
Why It Scores 8.0 — And The Label Line Behind Each Number
Purity & form
25% of scorePlain free-form glycine, vegetarian, non-GMO and gluten-free, no blend — the glycine the sleep studies used. Nothing disqualifying, and the brand's straightforward labeling is a plus. It scores level with the better capsules on purity; the ingredient itself is not the issue anywhere in this pick's ranking.
- Form
- Plain glycine capsules (1,000 mg each)
- Diet
- Vegetarian, non-GMO, gluten-free
Third-party testing
25% of scoreLife Extension's QC pedigree is among the most respected in the industry, and the brand makes a Certificate of Analysis available — real, credible verification for a commodity ingredient. It sits below Thorne's third-party certification and Pure Encapsulations' clinician-grade tier, but comfortably in the trustworthy range and ahead of budget capsules.
- Testing
- Life Extension QC, Certificate of Analysis available
Dose accuracy (3 g)
20% of scoreThe 1 g cap is good — three caps make the 3 g dose, the same as Thorne and Double Wood. It scores lower than those two on this axis because the small 100-count bottle means you are constantly managing supply to keep hitting the dose; dose accuracy in practice is partly about having enough capsules on hand, and a 33-night bottle strains that.
- Per serving
- 1,000 mg per capsule (so 3 g = 3 caps)
Taste & mixability
15% of scoreScored 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.
Value (per 3 g dose)
15% of scoreThe weak point. A 100-count bottle is only about 33 nights at the 3 g dose, and the cost per gram lands above the near-identical Double Wood, which ships 300 caps. You are paying a brand-and-COA premium for the same 1 g-cap format. Fair if you value the pedigree; not competitive on pure value.
- Bottle
- 100 capsules (~33 nights at the 3 g dose)
- Value
- Higher cost per gram than Double Wood; small bottle
- More Specs
- Positioning
- Brand explicitly labels glycine for healthy sleep
- Convenience
- Capsule — no scooping or mixing
Label verified. Every figure read from the Supplement Facts photo, Sep 7, 2026.
Marketing Claims Vs. Reality
1,000 mg of plain glycine per capsule.
The listing states 1,000 mg of glycine per capsule. This is the plain free-form glycine this ranking requires, and the 1 g cap is why the 3 g dose is three capsules rather than six — the claim holds as stated.
Certificate of Analysis available from a QC-respected brand.
Life Extension's QC reputation and availability of a Certificate of Analysis are well documented and central to the brand's positioning. Appropriate, credible verification for a commodity amino acid — the claim is accurate.
Vegetarian, non-GMO, gluten-free.
The product overview states a vegetarian, non-GMO, gluten-free formula, consistent with the plain-glycine capsule positioning. Accurate.
Promotes healthy 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. Life Extension's sleep positioning is a reasonable category claim, not a proven product-specific outcome.
What Our Test Actually Found
A good capsule held back by bottle size, not quality
There is nothing wrong with the glycine or the format here: plain 1,000 mg caps, so the studied 3 g dose is three capsules, from a brand with a genuinely strong QC reputation and a published COA. What drags it to #7 is arithmetic — the 100-count bottle covers only about 33 nights at the full dose, so you reorder roughly every month. For a supplement you take nightly and long-term, that reorder cadence and the higher resulting cost per gram matter, even though each individual capsule is excellent.
The COA is the real reason to choose it over Double Wood
Life Extension and Double Wood are the same format — plain glycine, 1,000 mg per cap, three caps to the 3 g dose — so the tiebreaker is what you value. Double Wood ships 300 caps at a lower cost per gram; Life Extension ships 100 caps at a higher one, but brings a stronger QC pedigree and a published Certificate of Analysis. If that verification and brand trust are worth the premium to you, this is the pick; if price is what matters, Double Wood (#6) is the better buy in the identical format.
A powder still wins on value outright
As with every capsule here, it is worth being plain: the glycine is chemically identical to the bulk powders, and a powder (#1 to #3) beats this on value outright — cheaper per gram and one 3 g scoop instead of three caps plus frequent reorders. Life Extension's appeal is the combination of capsule convenience and a trusted QC brand with a COA; it is not, and does not try to be, the cost-efficiency pick.
Same gentle effect, same honest caveat
The QC-brand 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 three caps nightly for one to two weeks before judging, and stack it with a cool room and consistent sleep timing. It is a trustworthy way to take glycine for sleep — it is still a small, well-tolerated edge, not a cure.
Full analysis: all pros & cons (8), buy if / skip if
- 1 g per capsule keeps the 3 g dose to three caps
- Life Extension's QC pedigree is among the most respected, with a published COA
- Plain glycine, vegetarian, non-GMO, gluten-free
- Brand explicitly positions glycine for healthy sleep — straightforward labeling
- Capsule convenience with a strong verification story
- 100-count bottle is small — only ~33 nights at the full 3 g dose, so you reorder often
- Cost per gram is higher than Double Wood for the same 1 g-capsule format
- A powder (#1 to #3) beats it on value outright
- You are a Life Extension loyalist and value the brand's published COA
- You want a single-cap 1 g glycine so the 3 g dose is three caps, not six
- You want a QC-respected brand that explicitly positions glycine for healthy sleep
- You do not mind reordering a smaller bottle more often
- You want the same 1 g-cap format cheaper — Double Wood (#6) ships 300 caps for less
- You want a long-running supply — a 100-count bottle is only ~33 nights
- Cost per gram is your priority — a powder (#1 to #3) beats it outright
Plain, vegetarian, non-GMO glycine at 1,000 mg per capsule (so 3 g is three caps) from a QC-respected brand with a published Certificate of Analysis. The catch is economics: the 100-count bottle covers only about 33 nights at the full dose, and it costs more per gram than the near-identical Double Wood. A fine pick for brand loyalists; for the same format at a better price, Double Wood (#6) wins.
Life Extension makes a perfectly good 1,000 mg glycine capsule, and the brand's QC reputation and published Certificate of Analysis give it real credibility. It is plain, vegetarian and non-GMO, the brand explicitly positions it for healthy sleep with straightforward labeling, and the 1 g cap keeps the studied 3 g dose to three capsules rather than six. The reason it sits at #7 rather than higher is pure economics, not quality. The bottle is only 100 capsules — about 33 nights at the 3 g sleep dose — so you reorder often, and the cost per gram lands above the near-identical Double Wood. If you are already a Life Extension loyalist who values the brand's COA and want a single-cap glycine with a strong QC story, it is a fine choice. For the same capsule format at a better price, Double Wood (#6) wins, and any powder beats it on value outright. Here is the full breakdown.
A good QC-brand 1 g cap — buy it for the COA and brand trust; Double Wood wins the same format on price.
Life Extension Glycine is a solid, trustworthy 1,000 mg single-cap glycine, and the brand's QC reputation and published Certificate of Analysis give it real credibility. It is plain, vegetarian and non-GMO, positioned for healthy sleep with straightforward labeling, and the 1 g cap keeps the studied 3 g dose to three capsules. It sits at #7 purely on economics. The bottle is only 100 capsules — about 33 nights at the 3 g dose — so you reorder often, and the cost per gram lands above the near-identical Double Wood. If you are a Life Extension loyalist who values the brand's COA, it is a fine choice. But for the same capsule format at a better price, Double Wood (#6) wins, and any powder (#1 to #3) beats it on value outright. As with every pick, take 3 g (three caps), 30 to 60 minutes before bed, give it one to two weeks, and stack it with good sleep timing and a cool room.
If This Doesn’t Fit — Try These
06Double Wood Glycine
If you've decided on capsules and value is your priority, Double Wood is the answer.
04Thorne Glycine
If you want capsules instead of powder, Thorne is the one to beat — the testing pedigree is the best here, it's a brand clinicians and pro teams actually rely on, and crucially it's a 1 g capsule, so hitting the 3 g dose takes three caps rather than six.
03BulkSupplements Glycine Powder
For the lowest cost per gram with real per-batch testing, this is the one to buy.
Quick Answers
How many capsules is the dose, and how long does the bottle last?
Three capsules make the dose, but the bottle is small — about 33 nights. Life Extension portions 1,000 mg of glycine per capsule, so the studied 3 g pre-bed dose (Yamadera 2007; Bannai 2012, PMID 22529837) is three caps. But the bottle holds only 100 capsules, which at three a night is roughly 33 nights — so you reorder often. That small bottle is the main reason it sits at #7 despite a good 1 g-cap format.
Does it come with a Certificate of Analysis?
Yes. Life Extension's QC pedigree is among the most respected in the industry, and the brand makes a Certificate of Analysis available for its products — real credibility for a commodity ingredient where verified purity is the whole point. It is a genuine strength and part of why the brand has the reputation it does; the reason it does not rank higher is economics, not quality.
How is it different from Double Wood, which is also a 1 g cap?
Same format, better price on the other side. Both are plain glycine at 1,000 mg per capsule, so both put the 3 g dose at three caps. Double Wood ships 300 capsules (about 100 nights) at a lower cost per gram, while Life Extension ships 100 capsules (about 33 nights) at a higher cost per gram. If you want the same capsule format at a better price, Double Wood (#6) wins; Life Extension is the pick mainly if you are already a brand loyalist who values its COA.
Is it plain glycine or a blend?
Plain glycine — vegetarian, non-GMO, gluten-free, no blend. The sleep evidence is for glycine by itself, so 'glycine complex,' NAC+glycine, and magnesium glycinate were disqualified from this ranking. Life Extension's capsule is the plain free-form glycine you want, and the brand explicitly positions it for healthy sleep with straightforward labeling.
Sources & Further Reading
3 sources — studies link to PubMed, product specs to the manufacturer
- [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] 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] 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.
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