- 01The sleep studies used about 3 grams at bedtime, which is not one capsule in the morning
Glycine's sleep signal comes from small trials giving about 3 grams shortly before bed. A single 850 mg capsule is under a third of that, and a morning pouch delivers it at the wrong end of the day for the sleep research. Glycine may still have other uses, but a morning capsule is not a test of the sleep studies.
- 02Glycine and TMG are different supplements
Trimethylglycine (TMG, also called betaine) is glycine with three extra methyl groups, and it is TMG, at grams a day, that lowers homocysteine in trials. Plain glycine has not been shown to do that, so a search for one does not answer questions about the other.
Glycine is the smallest of the amino acids (the building blocks of protein). The body makes its own, mainly from another amino acid called serine, and uses it in huge amounts to build collagen, the protein in skin, tendons and bone 4. As a supplement, its best-studied use is sleep: three small trials of about 3 grams taken before bed each found improvement on at least one sleep measure, such as how rested people felt 1. Beyond sleep, the evidence is one or two small trials per claim. Glycine is also often confused with trimethylglycine (TMG, or betaine), a different supplement with different evidence 10.
What is glycine?
Glycine is the simplest amino acid, and one analysis estimated that what the body makes plus what diet adds may fall about 10 grams a day short of all its jobs, a calculation rather than a measured shortage 4. What it is and what it does in your body has its own page. This guide covers the evidence, graded, how much studies use, when and how to take it, side effects, interactions, and blood tests worth knowing about.
Glycine has three jobs that drive supplement interest. It sits in every third position along the collagen chain, which lets the chain coil tightly. It is one of the three amino acids that make glutathione, a main antioxidant inside cells, alongside cysteine and glutamate 5. And in the brain and spinal cord, it works as a signaling chemical, both calming nerve signals and acting at NMDA receptors (receptors for the brain chemical glutamate) 3.
Glycine is found in protein-rich foods, and gelatin and collagen are especially rich in it. A 2026 review found that glycine and collagen supplements both raise blood glycine levels, with some sign that more glycine gives higher levels 1.
Glycine vs TMG
Search results mix up glycine and trimethylglycine (TMG), also called betaine. TMG is glycine carrying three methyl groups, and it donates them to convert homocysteine (an amino acid linked with heart and blood vessel risk when high) back into methionine. In a meta-analysis of 5 trials in healthy adults, at least 4 grams of betaine a day for 6 weeks or more lowered blood homocysteine by about 1.23 micromoles per liter 10. Plain glycine does not carry those methyl groups and has not been shown to do this, so the two are not interchangeable.
Glycine or TMG: two different supplements
What glycine is good for: the evidence, graded
Each use below carries a grade. Strong means several good randomized trials or a meta-analysis agree. Moderate means several randomized trials, mostly positive but small or short. Limited means few or small trials, or mixed results. Early means lab, animal or a single pilot study. Not supported means good trials found no benefit. Our guide to how supplements are regulated and studied explains why the grade matters.
| Use | What the research found | Evidence | Source |
|---|---|---|---|
| Sleep quality | 3 small trials of glycine before bed: all improved at least one sleep outcome | Limited | 1 |
| Next-day tiredness after short sleep | 3 g at bedtime during 3 nights of 25% less sleep: less fatigue, better reaction-time test | Limited | 2 |
| HbA1c in type 2 diabetes | 74 adults, 5 g a day for 3 months: HbA1c lower than placebo | Limited | 8 |
| Oxidative stress and blood pressure in metabolic syndrome | 60 adults, 15 g a day for 3 months: lower oxidative stress marker; systolic pressure lower in men only | Early | 9 |
| Glutathione in older adults | With NAC (GlyNAC), 24 older adults, 16 weeks: glutathione and several aging markers improved | Early | 5 |
| Collagen, skin and joints | A metabolic calculation of a possible shortfall; no outcome trials of glycine alone in the sources reviewed | Early | 4 |
| Schizophrenia symptoms, as an add-on | 157 people, 16 weeks: no better than placebo; no benefit added to clozapine | Not supported | 67 |
Is glycine good for sleep?
The evidence is small but points one way. A 2026 scoping review searched every major database and found three trials of glycine and sleep; all three reported benefit on at least one sleep-related outcome 1. The best-described one, from Japan, cut healthy volunteers' sleep by a quarter for three nights. Those given 3 grams of glycine before bed reported less fatigue and a trend toward less sleepiness the next day, and did better on a reaction-time test, compared with placebo 2. Glycine did not change melatonin, the body's sleep hormone 2.
The proposed mechanism comes from rats. Oral glycine increased deep (non-REM) sleep and shortened the time to fall asleep, while widening skin blood vessels and lowering core body temperature, a drop that normally comes before sleep. The effect ran through NMDA receptors in the suprachiasmatic nucleus, the brain's master clock 3.
All 3 glycine sleep trials reported benefits on at least 1 sleep-related outcome.
Three small trials is a thin base, and the outcomes were mostly how people felt rather than long-term sleep health. Our sleep calculator helps plan bedtimes around sleep cycles, which costs nothing to try alongside any change.
Blood sugar
In a Mexican trial, 74 adults with type 2 diabetes (average HbA1c 8%) took 5 grams of glycine a day or placebo for 3 months. HbA1c, the three-month blood sugar average, was significantly lower on glycine, and inflammation markers shifted 8. The abstract does not give the size of the HbA1c drop, and the trial has not been repeated at scale.
Type 2 diabetes and prediabetes are diagnosed and treated by a clinician, and glycine is not a treatment for either. It is never a swap for a prescribed diabetes medicine. Our guide to blood sugar tests explains HbA1c and fasting glucose.
Blood pressure and oxidative stress
In 60 adults with metabolic syndrome (a cluster of high blood pressure, blood sugar, waist size and blood fats), 15 grams of glycine a day for 3 months lowered a marker of oxidative damage (TBARS) by 25% compared with placebo, and systolic blood pressure fell in the men 9. That is a large daily amount, far above a capsule, and the blood pressure result was limited to one subgroup.
Glutathione and aging
Paired with NAC, glycine supplies two of glutathione's three building blocks. In a 16-week randomized trial of 24 older adults, the combination (GlyNAC) corrected low glutathione and improved oxidative stress, inflammation, insulin resistance, gait speed and strength, while placebo did not 5. It is a small study of a combination, so it says little about glycine alone.
Collagen, skin and joints
The case here is mostly theoretical. Collagen needs glycine at every third position, and the 2009 calculation suggests the body may be short of glycine for collagen-building 4. No trial in the sources reviewed tested glycine alone on skin, joints or bone outcomes, so the grade is Early.
Schizophrenia
Because glycine acts at NMDA receptors, psychiatrists tested high doses as an add-on for the negative symptoms of schizophrenia. In CONSIST, a 16-week trial of 157 people, glycine did no better than placebo for negative symptoms or thinking 6. In a trial of 60 grams a day added to clozapine, symptoms did not improve 7. Schizophrenia is treated by a psychiatrist, and glycine is not a treatment for it.
How much glycine do studies use?
These are the amounts trials used, recorded as research history, not a dose for anyone reading. Glycine is not a vitamin or mineral, so it has no recommended daily amount and no official upper limit.
| Use studied | Amount | Form | Duration | Source |
|---|---|---|---|---|
| Sleep, short-sleep recovery | 3 g before bed | By mouth | 3 nights | 2 |
| Type 2 diabetes | 5 g a day, split three times a day | By mouth | 3 months | 8 |
| Metabolic syndrome | 15 g a day | By mouth | 3 months | 9 |
| Schizophrenia with clozapine | 60 g a day | By mouth | 8 weeks | 7 |
One LifeFrom capsule holds 850 mg of glycine, under a third of the 3 grams used in the sleep research and a small fraction of the 5 to 15 grams used in the metabolic trials 289. Trials at 60 grams a day show how much has been given under medical supervision, not a level anyone should approach on their own 7.
When and how to take glycine
How glycine was taken in studies
Timing matters only for sleep, where the research gave glycine near bedtime 2. For other uses no time of day was tested, and no study tested taking it with or without food.
How long does glycine take to work? In the sleep research, effects were measured from the first nights 2. The blood sugar and oxidative stress trials measured at 3 months 89. Cycling glycine on and off has not been studied.
Glycine side effects
Glycine is a normal part of food, and the trials in this guide did not report serious problems. The GlyNAC trial described the combination as safe and well tolerated over 16 weeks 5, and a trial of 60 grams a day in schizophrenia reported no clinically significant worsening 7. No large or long safety studies exist for glycine supplements, so the honest summary is: few problems reported, little long-term data.
| Common and usually mild | Less common, needs prompt care |
|---|---|
| No consistent mild side effect was reported in the trials reviewed 57 | Hives, swelling of the face or throat, or trouble breathing: call 911 |
| Sleepiness, if taken near bedtime as in the sleep trials 2 | New confusion, agitation or worsening psychiatric symptoms in someone on antipsychotic medicine: same-day care |
| Shakiness, sweating or confusion on a diabetes medicine, which can mean low blood sugar: same-day care |
Who should avoid glycine or ask first
- Pregnancy and breastfeeding: glycine from food is normal, but supplement doses have not been studied in pregnancy or breastfeeding in the sources reviewed. Ask your obstetric clinician first.
- Children: no supplement trials in children were found in the sources reviewed; ask the child's clinician.
- Schizophrenia and antipsychotic medicines: glycine was no better than placebo as an add-on, and less effective alongside clozapine 67. Psychiatric medicines should only be changed with the prescriber.
- Diabetes: glycine lowered HbA1c in one trial, which could add to diabetes medicines 8.
- Kidney or liver disease: no glycine supplement data in these conditions were found in the sources reviewed; ask your specialist first.
- Surgery: no specific surgical warning was found in the sources reviewed; tell the surgical team about every supplement.
Glycine interactions
| Medicine | What can happen | Why | What to do |
|---|---|---|---|
| Clozapine | No added benefit; glycine-site agents appear less effective with clozapine | Clozapine already acts on the glutamate system 7 | Talk to the psychiatrist before combining |
| Other antipsychotics | No benefit for negative symptoms or thinking in a large add-on trial | Tested in CONSIST 6 | Talk to the prescriber; never change psychiatric medicine on your own |
| Insulin and other diabetes medicines | Blood sugar could run lower | Glycine lowered HbA1c in one trial 8 | Talk to the prescriber first; they may want closer glucose checks |
| Sleep medicines and sedatives | Not studied together | Glycine is studied for sleepiness at bedtime 2 | Ask a pharmacist before combining |
Supplements to pair with glycine or keep apart
No study has set a gap in hours between glycine and another supplement, so this table flags pairings and overlaps. Everything in a pouch is taken at once.
| Supplement | Together or apart | Why |
|---|---|---|
| NAC | Together in trials | The GlyNAC trial paired them to supply two glutathione building blocks 5 |
| Magnesium | Together is common | Magnesium glycinate already contains a small amount of glycine; both are popular for sleep |
| L-theanine | Overlap | Also used for relaxation and sleep; no interaction reported, but sleep aids can add up |
| Valerian | Overlap, ask first | A sedating herb; stacking sleep aids is best discussed with a pharmacist |
Blood tests worth knowing about
No routine blood test tracks glycine supplements, and blood glycine is not a standard lab test. For sleep, a simple sleep diary (bedtime, time to fall asleep, wake-ups, how rested you feel) is the honest way to see whether anything changes. The markers below matter only for specific situations. Ask your clinician whether any of them make sense for you.
| Marker | Why it matters with glycine | When it is usually checked |
|---|---|---|
| HbA1c | Lower in one 3-month diabetes trial 8 | Every 3 to 6 months in diabetes care |
| Fasting glucose | A low reading on diabetes medicine matters if glycine adds to it | Routine checkups and diabetes care |
| Homocysteine | Lowered by TMG (betaine), not by plain glycine 10 | When a clinician is assessing B-vitamin status or vascular risk |
A high homocysteine result is a reason to see a clinician, who will usually check B12 and folate first, not a reason to start glycine or TMG.
Conditions and goals glycine comes up around
Glycine is searched most alongside sleep, blood sugar and collagen. Insomnia and sleep apnea are diagnosed and treated by clinicians, and long-term poor sleep is worth raising at a visit. Prediabetes and type 2 diabetes are diagnosed from fasting glucose or HbA1c and managed by a clinician. Glycine is not a treatment for any of these, and it is never a swap for a prescribed medicine.
Glycine in the LifeFrom pouch
| In the LifeFrom pouch | |
|---|---|
| Product | Glycine |
| What one serving holds | 1 capsule: L-Glycine, 850 mg |
| Form | Capsule; vegan capsule (hypromellose) |
| How it is packed | One serving in each of your 30 daily pouches, with up to 8 supplements per pouch |
| Price | $8.40 a month, plus the fixed $28.50 a month packing, handling and US delivery line for the whole pouch, not per supplement. Prices as of November 2026; the shop shows the current price |
| Curated packs that include it | None |
One capsule holds 850 mg, under a third of the 3 grams used before bed in the sleep research and far below the 5 to 15 grams a day in the metabolic trials 289. The pouch is a morning pouch, so its glycine is taken at the opposite end of the day from the sleep studies. See the shop and its packs.
This guide is general education, not medical advice, and it cannot diagnose you. Dietary supplements, glycine included, are not approved by the FDA for safety or effectiveness before they are sold. The clinician who knows your history and medicines is the right person to decide whether glycine fits. Read our medical disclaimer for more.
Citations
- Fan Z, Nelson JM, Wallace TC. Glycine bioavailability and sleep-related outcomes following oral glycine and collagen supplementation: a scoping review. J Diet Suppl. 2026;23:602-622.
- Bannai M, Kawai N, Ono K, Nakahara K, Murakami N. The effects of glycine on subjective daytime performance in partially sleep-restricted healthy volunteers. Front Neurol. 2012;3:61.
- Kawai N, Sakai N, Okuro M, et al. The sleep-promoting and hypothermic effects of glycine are mediated by NMDA receptors in the suprachiasmatic nucleus. Neuropsychopharmacology. 2015;40(6):1405-1416.
- Meléndez-Hevia E, De Paz-Lugo P, Cornish-Bowden A, Cárdenas ML. A weak link in metabolism: the metabolic capacity for glycine biosynthesis does not satisfy the need for collagen synthesis. J Biosci. 2009;34(6):853-872.
- Kumar P, Liu C, Suliburk J, et al. Supplementing glycine and N-acetylcysteine (GlyNAC) in older adults improves glutathione deficiency, oxidative stress, mitochondrial dysfunction, inflammation, physical function, and aging hallmarks: a randomized clinical trial. J Gerontol A Biol Sci Med Sci. 2023;78(1):75-89.
- Buchanan RW, Javitt DC, Marder SR, et al. The Cognitive and Negative Symptoms in Schizophrenia Trial (CONSIST): the efficacy of glutamatergic agents for negative symptoms and cognitive impairments. Am J Psychiatry. 2007;164(10):1593-1602.
- Evins AE, Fitzgerald SM, Wine L, Rosselli R, Goff DC. Placebo-controlled trial of glycine added to clozapine in schizophrenia. Am J Psychiatry. 2000;157(5):826-828.
- Cruz M, Maldonado-Bernal C, Mondragón-Gonzalez R, et al. Glycine treatment decreases proinflammatory cytokines and increases interferon-gamma in patients with type 2 diabetes. J Endocrinol Invest. 2008;31(8):694-699.
- Díaz-Flores M, Cruz M, Duran-Reyes G, et al. Oral supplementation with glycine reduces oxidative stress in patients with metabolic syndrome, improving their systolic blood pressure. Can J Physiol Pharmacol. 2013;91(10):855-860.
- McRae MP. Betaine supplementation decreases plasma homocysteine in healthy adult participants: a meta-analysis. J Chiropr Med. 2013;12(1):20-25.
Educational context only, not medical advice or a diagnosis. Always discuss your results with a clinician.
