Type the glycine in one serving of your powder or capsules — or the magnesium on a magnesium glycinate label — and how many servings you take before bed. You see it against the 3 g every sleep trial of glycine alone gave, who those trials gave it to, and what they found.
Your glycine before bed is
Less than the 3 g the sleep trials gave 1 g of glycine before bed — 33% of the trials’ 3 g
The trials’ 3 g is 3 of your 1,000 mg servings.
Of the 3 placebo-controlled sleep trials of glycine alone we could find, all 3 reported a benefit on at least one measure — every one gave 3 g before bedtime, every one came from one company’s research group (Ajinomoto, which makes glycine), and each had 7 to 19 people analysed.
| Trial | Who | Gave | Found |
|---|---|---|---|
| Inagawa 2006 | 19 women with poor sleep | 3 g before bed | less fatigue the next morning |
| Yamadera 2007 | 11 adults with poor sleep | 3 g before bed | asleep and in deep sleep sooner in a sleep lab; better-rated sleep |
| Bannai 2012 | 10 men (7 analysed), sleep cut by 25% | 3 g, 30 min before bed, 3 nights | less next-day fatigue; a better vigilance test |
The 2026 scoping review of glycine and sleep: “All 3 glycine sleep trials reported benefits on at least 1 sleep-related outcome.” “Larger mechanistic trials with standardized sleep outcomes are needed.”
This is not medical advice. No official body sets a dose or an upper limit for glycine; this shows what the trials gave, not what you should take. Talk to your doctor or pharmacist before adding a supplement — especially if you take medicines for sleep, mood or blood pressure, or are pregnant or breastfeeding.
Every placebo-controlled sleep trial of glycine alone gave 3 g before bedtime. There are three, all small crossovers (7 to 19 people analysed), all from one company’s research group, and all three reported a benefit on at least one measure. No official body sets a dose or an upper limit for glycine. A 1,000 mg capsule is a third of 3 g; magnesium glycinate carries far less.
How to use it
Type one serving from your label — grams of glycine (powders print grams per scoop), milligrams of glycine (capsules), or, for a magnesium glycinate, the milligrams of magnesium its Supplement Facts panel prints — and how many servings you take before bed. You see the glycine against the trials’ 3 g, how many of your servings make 3 g, and the three trials as they were run. “About the same” means within 10% of 3 g (2.7 to 3.3 g) — a band of ours, not a dose. The tool never suggests an amount.
The three trials
All three come from Ajinomoto’s research group — the company makes glycine — and its 2012 review says so: “We have previously reported three human volunteer studies to subjectively assess the effect of glycine on sleep.” “Individuals with continuous complaints about the quality of their sleep were recruited and given either 3 g of glycine or a placebo before bedtime.”
| Trial | How it was run | Who | Dose |
|---|---|---|---|
| Inagawa 2006 | randomized, double-blind, crossover, against a placebo | 19 women aged 24 to 53 with continuing complaints about their sleep (PSQI 6 or more) | 3 g before bedtime |
| Yamadera 2007 | randomized, single-blind, crossover, against a placebo | 11 adults (8 women, 3 men) aged 30 to 57 with repeated unsatisfactory sleep | 3 g before bedtime |
| Bannai 2012 | randomized, single-blind, crossover, against a placebo | 10 healthy men aged 30 to 61 (7 analysed) whose sleep was cut by 25% for three nights | 3 g, 30 minutes before bedtime, three nights |
Inagawa 2006 has no abstract online; its authors’ 2012 review describes it: “Glycine significantly improved the feeling of fatigue the next morning, indicating that glycine helps improve sleep quality.” Yamadera 2007 measured sleep overnight in a sleep lab: “Glycine improved subjective sleep quality and sleep efficacy (sleep time/in-bed time), and shortened PSG latency both to sleep onset and to slow wave sleep without changes in the sleep architecture.” “Glycine lessened daytime sleepiness and improved performance of memory recognition tasks.” Bannai 2012 measured the day after short sleep, not sleep itself: “This was a randomized single-blinded crossover trial.” “In subjects given glycine, the VAS data showed a significant reduction in fatigue and a tendency toward reduced sleepiness.” “PC performance test revealed significant improvement in psychomotor vigilance test.”
What the reviews say
The 2026 scoping review (Fan, Nelson and Wallace, J Diet Suppl), which searched four databases to July 2026, found that “3 investigated supplemental glycine and sleep-related outcomes” — these three — and: “All 3 glycine sleep trials reported benefits on at least 1 sleep-related outcome.” “Larger mechanistic trials with standardized sleep outcomes are needed.” Schuster 2025, a magnesium trial, put it this way: “While evidence remains inconclusive, some studies suggest that glycine supplementation at a dose of 3 g can enhance sleep quality and reduce daytime fatigue, highlighting its potential as a supportive agent in sleep management.” Left out of the count, and why: blends that hold glycine among other ingredients (Langan-Evans 2023; Jackson 2026, which found trivial effects), collagen, and the makers’ open daytime safety study, which had no placebo and no sleep measure.
Magnesium glycinate: how much glycine is in it
NIH ODS: “The Supplement Facts panel on a dietary supplement label declares the amount of elemental magnesium in the product, not the weight of the entire magnesium-containing compound.” Magnesium bisglycinate is Mg(C2H4NO2)2 — two glycines to each magnesium — so by the IUPAC atomic weights each milligram of magnesium carries at most 6.177 mg of glycine. Schuster 2025’s capsules agree within 1.5%: “Each capsule contained 893 mg of magnesium bisglycinate, corresponding to 125 mg of magnesium and 761.5 mg of glycine, providing a total daily dose of 250 mg of magnesium and 1523 mg of glycine.” A “buffered” product, mixed with another form of magnesium, carries less.
| Magnesium on the label | Glycine in it | Of the trials’ 3 g |
|---|---|---|
| 100 mg | 0.62 g | 21% |
| 200 mg | 1.24 g | 41% |
| 250 mg | 1.54 g | 51% |
| 350 mg | 2.16 g | 72% |
To carry 3 g of glycine a glycinate would need about 486 mg of magnesium — and NIH ODS: “The Tolerable Upper Intake Level for supplemental magnesium is 350 mg for adults, and it ranges from 65 to 350 mg for children and adolescents, depending on age.” So magnesium glycinate taken at or under that limit does not reach the glycine trials’ amount. For the magnesium itself, see Magnesium for Sleep.
Capsules and scoops
| One serving | Servings for 3 g |
|---|---|
| 500 mg capsule | 6 |
| 1,000 mg capsule | 3 |
| 1.5 g scoop | 2 |
| 3 g scoop | 1 |
What is not known
No official body — not NIH ODS, NCCIH or MedlinePlus — publishes a glycine fact sheet, a dose or an upper limit. The trials were short crossovers; Bannai 2012 ran three nights. The makers’ own open safety study gave 9 g in the daytime to 12 people — “This study was an open trial because any safety problems needed to be addressed quickly if they occurred.” — and reported: “Glycine (9 g) administered during the day did not induce sleepiness and had no adverse effects.” That is one small study without a placebo, not a limit. No trial here studied pregnancy, breastfeeding or anyone under 18.
Worked examples
- One 1,000 mg capsule (the page’s example): 1 g — a third of the trials’ 3 g; the trials’ 3 g is 3 of those capsules.
- Two 1.2 g scoops: 2.4 g — 80%, under the 2.7 g band.
- One 3 g scoop: about the 3 g the trials gave.
- Magnesium glycinate, 200 mg of magnesium: at most 1.24 g of glycine — 41%.
Common mistakes
- Counting the compound as glycine. A magnesium glycinate’s milligrams are magnesium, and the glycine with it is about six times that, at most.
- Counting a blend. A sleep blend that lists glycine among five or eight ingredients is not what the glycine trials tested.
- Reading “3 g” as a dose someone set. It is the amount three small trials used; no official body has set one.
Frequently asked questions
Does glycine help you sleep?
Three small placebo-controlled trials of 3 g before bedtime each reported a benefit on at least one measure — less next-morning fatigue, falling asleep and reaching deep sleep sooner in a sleep lab, less fatigue after short sleep. All three came from the company that makes glycine, and the 2026 review says larger trials are needed.
How much glycine for sleep?
Every sleep trial gave 3 g. No official body sets a dose; this page places your amount against the trials’ 3 g and does not suggest one.
When should you take glycine for sleep?
Before bedtime in all three trials; Bannai 2012 gave it 30 minutes before.
How many glycine capsules make 3 grams?
Three 1,000 mg capsules, or six 500 mg capsules. A 3 g scoop of powder is one serving.
Does magnesium glycinate have enough glycine for sleep?
Not the trials’ amount: 200 mg of magnesium as glycinate carries at most 1.24 g of glycine, and reaching 3 g would take about 486 mg of magnesium — above the NIH’s 350 mg upper limit for magnesium from supplements.
Is glycine safe to take every night?
No official body has set a limit or studied it for long. The sleep trials were short; the makers’ open study gave 9 g in one day without problems in 12 people. Ask your doctor or pharmacist, especially if you take other medicines, are pregnant or breastfeeding.
More sleep tools: Magnesium for Sleep, L-Theanine for Sleep, Valerian for Sleep, the Melatonin Dose & Timing calculator and Tart Cherry Juice for Sleep.
Read next
This is not medical advice, and nothing here diagnoses, treats or prevents anything. It shows what the glycine sleep trials gave and found; no official body sets a dose or an upper limit for glycine. Talk to your doctor or pharmacist before adding a supplement — especially with medicines for sleep, mood or blood pressure, or in pregnancy. Some links on this site are affiliate links: I buy what I review at full price, and a commission never changes a verdict.