SupplementsAmino AcidsGlycine

Glycine

listed on the label as L-glycine

The smallest amino acid, in every third spot of your collagen and possibly a quiet help at bedtime.

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A pale glycine capsule
Builds up
Same night
In your body
No clean number
Per 1 capsule
850 mg
30-day supply
$8.40One capsule a day, plus packing and delivery

What is glycine?

Glycine is the simplest amino acid there is. Your body can make it, so it isn't officially essential. But some researchers think we fall short: one analysis estimated that what you make plus what you eat comes to several grams a day, roughly 10 g less than your body would like to use.

Most of that demand comes from collagen, the protein that holds your skin, joints and bones together. Glycine sits in every third position along the collagen chain, helping it hold its triple twist.

It's also the glycine in magnesium glycinate, the amino acid that magnesium is bound to. Ours is plain glycine, 850 mg in each capsule.

What it does

  • CollagenA key building block of collagen for skin, joints and bones.
  • SleepSupports restful sleep.
  • Antioxidant defensesYour body uses it to make glutathione, one of its main antioxidants.
  • Nerve signalsPlays a part in normal signaling in your brain and spinal cord.

These statements have not been evaluated by the FDA. This product is not intended to diagnose, treat, cure or prevent any disease.

The full guide · 13 min readGlycine benefits, side effects and sleep: what the evidence showsWhich form, how much, when to take it, and whether it's worth it, with the studies behind each answer.

What people take it for

How long it takes

Sleep studies looked at the very night people took it and the day after. For glutathione in older adults, trials ran from a couple of weeks to about 6 months.

Glycine in your blood, night by nightTypical pattern
Up, then used again
Night 1Night 7
  1. Before bedWhen sleep studies gave it
  2. The next dayWhen people felt less tired, after short nights
  3. Weeks to monthsHow long glutathione studies with NAC ran

How long it stays in your body

We couldn't find a clean half-life figure. Your body uses glycine for so many jobs that it's in constant demand, so as far as we can tell it doesn't stack up from one night to the next.

What's in a capsule

One capsule holds 850 mg. The sleep studies used 3 g before bed, so one capsule holds less than those studies gave.

How something this simple may help you sleep

It may come down to temperature. Your core temperature drops as you fall asleep. In rats, glycine opened up blood vessels in the skin, so heat escaped and the core cooled. It seems to act on the brain's master clock, a tiny region called the SCN, without changing melatonin levels. That's rat work, so we can't be sure it happens the same way in people.

It's also a raw material for glutathione, your body's main home-grown antioxidant. Older adults tend to run low, and in one small study, a mix of glycine and cysteine brought it up to the levels seen in younger adults. Later trials used glycine with NAC, which supplies the cysteine.

There's a blood sugar link as well. People with insulin resistance often have low glycine, and a large amount taken with sugar cut the rise in blood sugar by more than half in one study. Interesting, but it's early, and nobody should swap their medicine for it.

Read the full guide to glycine

What it interacts with

Goes well with

Side effects

  • Generally well tolerated in studies, including trials lasting up to 24 weeks with NAC.
  • Rarely, allergic reactions such as hives or swelling. Stop and get help if you have trouble breathing.

Check first if

  • Schizophrenia or taking clozapine: talk to your psychiatrist first.
  • Epilepsy or taking seizure medicine: talk to your doctor first.
  • Pregnancy or breastfeeding: it's not known how glycine affects either, so check with your doctor.

The blood tests that go with it

Work it out

A sleeping eye resting against crisp white linenSleep, cycle and pregnancy · CalculatorSleep calculatorWhen to go to bed, or when to wake.A clean fork and an empty plate, composed like jewelleryBlood sugar · CalculatorHOMA-IR calculatorInsulin resistance from fasting glucose and insulin.A single drop of blood on a fingertipBlood sugar · CalculatorA1C calculatorAverage glucose to A1C, and back.

Supplementation

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These statements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure or prevent any disease.

Want it more precise? Get the app.

A page can only tell you about Glycine. The app tells you about you: whether it fits, when to take it, and whether it's working.

  • Checked against your blood work and everything you already take
  • On your daily timeline, around your sleep, training and meals
  • Followed over time, so you can see what moved
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Glycine against your blood work, your sleep and what you already take.

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Questions

What is glycine good for?

People mostly use it for sleep and next-day tiredness. Your body also uses it to make collagen and glutathione.

How long does glycine take to work?

Sleep studies gave it before bed and looked at that same night and the following day. Effects on glutathione took weeks.

What are the side effects of glycine?

It's generally well tolerated. Allergic reactions are rare but possible, so stop and get help if you have swelling or trouble breathing.

Does glycine help you sleep?

It looks promising. Small studies found people slept better and felt less tired the next day, at 3 g before bed. One capsule holds less than that.

Who should not take glycine?

Talk to a doctor first if you take clozapine, seizure medicines, memantine or diabetes medicines, or if you're pregnant or breastfeeding.

Can I take glycine every day?

Studies with NAC gave it daily for up to 24 weeks and it was well tolerated. We know less about longer use on its own.

Does glycine help collagen?

It's a third of collagen by count, so your body needs a lot. That doesn't prove extra glycine builds more collagen, but it's why people take an interest.

Is glycine the same as magnesium glycinate?

No. Magnesium glycinate is magnesium bound to glycine. Ours here is glycine alone, with no magnesium.

Does glycine lower blood sugar?

A large amount cut the rise in blood sugar after glucose in one study. It's early, and if you take diabetes medicine, talk to your doctor before adding it.

Sources
  1. Bannai M et al. The effects of glycine on subjective daytime performance in partially sleep-restricted healthy volunteers. Front Neurol, 2012.
  2. Yamadera W et al. Glycine ingestion improves subjective sleep quality in human volunteers, correlating with polysomnographic changes. Sleep Biol Rhythms, 2007.
  3. Inagawa K et al. Subjective effects of glycine ingestion before bedtime on sleep quality. Sleep Biol Rhythms, 2006.
  4. Kawai N et al. The sleep-promoting and hypothermic effects of glycine are mediated by NMDA receptors in the suprachiasmatic nucleus. Neuropsychopharmacology, 2015.
  5. Melendez-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.
  6. Razak MA et al. Multifarious beneficial effect of nonessential amino acid, glycine: a review. Oxid Med Cell Longev, 2017.
  7. Sekhar RV et al. Deficient synthesis of glutathione underlies oxidative stress in aging. Am J Clin Nutr, 2011.
  8. Kumar P et al. Supplementing glycine and N-acetylcysteine (GlyNAC) in older adults. J Gerontol A, 2023.
  9. Kumar P et al. Glycine and N-acetylcysteine (GlyNAC) supplementation in older adults: results of a pilot clinical trial. Clin Transl Med, 2021.
  10. Gannon MC et al. The metabolic response to ingested glycine. Am J Clin Nutr, 2002.
  11. White PJ et al. Insulin action, type 2 diabetes, and branched-chain amino acids: a two-way street. Mol Metab, 2021.
  12. Potkin SG et al. Effect of clozapine and adjunctive high-dose glycine in treatment-resistant schizophrenia. Am J Psychiatry, 1999.

Written by LifeFrom from these sources, and not yet reviewed by a clinician. Talk to your doctor before starting a supplement.

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