Experiment guides → Supplements → Glycine
Does glycine help you sleep?
Quick answer: possibly — on the strength of three small trials, all using the same dose. Three grams of glycine before bed improved how people rated their sleep, shortened the time it took them to reach deep sleep on polysomnography, and reduced next-day sleepiness when nights were cut short. The catch: the samples were 11 to 19 people, and all the work came from one amino-acid manufacturer. Glycine is cheap, tastes faintly sweet and has a good safety record, which makes it one of the easier supplement claims to test on yourself for two weeks.
"I will take 3 g of glycine 30 minutes before bed for 14 nights."
What the research says
Sleep quality and time-to-deep-sleep, with polysomnography. Yamadera and colleagues gave 3 g of glycine or placebo before bed to volunteers who complained about their sleep. Glycine improved subjective sleep quality and reduced how long it took to fall asleep and to reach slow-wave sleep, measured with overnight recordings, without altering sleep architecture. The sample was small (11 completed the polysomnography arm) (Yamadera et al., 2007).
Less fatigue the next day. In an earlier crossover study, 19 women with sleep complaints took 3 g of glycine before bed and reported less fatigue and more liveliness the following morning compared with placebo, on validated questionnaires (Inagawa et al., 2006).
It also softened the cost of short nights. Bannai and colleagues restricted healthy volunteers to 5.5 hours in bed for three nights. Those taking 3 g of glycine reported less daytime sleepiness and fatigue than the placebo group, and performed slightly better on a psychomotor vigilance task. In animal work the same group traced the effect to lowered core body temperature via NMDA receptors in the brain's clock — plausible mechanism, small human data (Bannai et al., 2012).
What this evidence doesn't say
Three trials, one dose, tiny samples, all funded by the company that sells glycine, and no independent replication in a general adult population. The polysomnography results are the strongest part; the subjective results could partly be expectation. Nothing here says glycine treats insomnia — the participants were ordinary poor sleepers, not patients.
Run it as an experiment
- Baseline five nights. Morning ratings: sleep quality, restedness, time-to-sleep. Add a note if you woke unrefreshed — that's the outcome the trials found most responsive.
- Use the trial dose. 3 g of glycine powder dissolved in water, about 30 minutes before bed. Don't improvise a higher dose — the evidence only covers this one.
- Make the pact. "I will take 3 g of glycine 30 minutes before bed for 14 nights." Keep caffeine, alcohol and bedtime unchanged.
- Check in each morning. Same three ratings. If you have a wearable, note deep-sleep minutes too, but don't let it overrule how you feel — the trackers are least accurate exactly there.
- Compare and, if it helped, retest. Restedness first, then time-to-sleep. A clear improvement is worth a week off and a second block to confirm; no change means you can cross a cheap one off the list.
What to expect
The trial signals were about waking more refreshed and getting to deep sleep a bit sooner, not about sleeping longer. If glycine works for you, expect mornings that feel less heavy rather than a dramatically different night. Glycine has a mild sweet taste and no known hangover effect; if nothing shifts in 14 nights, the honest reading is that it isn't your lever.
Who should skip this
Glycine can interact with clozapine and may not be appropriate in kidney or liver disease; pregnant or breastfeeding people should ask a doctor first. If you take any psychiatric medication, check with your prescriber before adding an amino acid that acts on brain receptors.
Frequently asked questions
How much glycine should I take for sleep?
All three trials used 3 g before bed. There's no evidence that more helps, and higher doses mostly test your stomach. Three grams is about a level teaspoon of powder.
Is glycine better than magnesium for sleep?
No head-to-head trial exists. Glycine's trials measured deep sleep and next-day alertness in ordinary poor sleepers; magnesium's measured sleep onset in older adults with insomnia. Different outcomes, different people. If you're curious, test them in separate 14-night blocks — not together.
Does glycine make you sleepy?
Not in the sedative sense — the trials found no daytime drowsiness, and the mechanism proposed is a slight drop in core temperature, which is what your body does naturally at sleep onset. Think of it as a nudge rather than a knockout.
Related experiments
Sources
- Yamadera W, Inagawa K, Chiba S, et al. Glycine ingestion improves subjective sleep quality in human volunteers, correlating with polysomnographic changes. Sleep Biol Rhythms. 2007;5:126–131. DOI
- Inagawa K, Hiraoka T, Kohda T, Yamadera W, Takahashi M. Subjective effects of glycine ingestion before bedtime on sleep quality. Sleep Biol Rhythms. 2006;4:75–77. DOI
- 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. PubMed 22529837
- 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. PubMed 25533534
Track this experiment in N of 1
A few baseline nights, then the change — and your own mornings deliver the result. No streaks, no guilt. Your first experiment is free.
Downloadon the App StoreThis page is general information about published research, not medical advice. Glycine may interact with some psychiatric medicines; talk to your doctor or pharmacist before starting it, especially if you're pregnant or take prescription medication.