Glycine for sleep: how 3g before bed lowers body temperature
Glycine for sleep: the amino acid that helps your body cool down
Time to effect
Dose
▪ The challenge at hand
Poor sleep onset — lying awake unable to cross the threshold into sleep despite feeling tired, is one of the more common and understated sleep complaints. Most sleep advice focuses on anxiety reduction or sleep hygiene, but some people find the issue is physical: the body simply doesn't cool down quickly enough to trigger sleep.
Glycine, a naturally occurring amino acid, addresses this through a thermoregulatory mechanism rather than sedation: it accelerates the decline in core body temperature that signals the brain to initiate sleep. It doesn't affect anxiety, doesn't sedate, and works on a side of the sleep equation that most sleep aids ignore entirely.
▪ What it is
Glycine is a naturally occurring amino acid — one of the building blocks of protein — sold cheaply as a standalone powder or capsule. It's used here specifically for its effect on body temperature and sleep onset.
▪ Why this is surprising
Glycine doesn't sedate you the way a sleeping pill does. It works by accelerating the natural drop in core body temperature that signals your brain it's time to sleep — a thermoregulatory mechanism that's almost entirely absent from mainstream sleep medicine. That makes it useful for people who can't tolerate conventional sleep aids or have run out of standard sleep-hygiene options.
▪ How it works
Cooling down, not sedating.
Glycine promotes peripheral vasodilation — widening the blood vessels in your hands and feet — which speeds up heat loss and the decline in core body temperature that initiates sleep. It also acts on NMDA receptors in the suprachiasmatic nucleus, the brain's master clock. The effect is a faster, easier transition into sleep without the grogginess of a sedative.
▪ The research
What the evidence says
A widely-cited review summarizing earlier human trials reports that 3g of glycine taken before bed improved subjective sleep quality in people with insomnia tendencies, reduced the time it took to fall asleep, and improved next-day alertness — without the side effects of sedatives. The mechanism was traced to glycine lowering core body temperature via vasodilation. The evidence is promising but rated moderate: the trials are small.
Bannai M & Kawai N. J Pharmacol Sci. 2012;118(2):145-8. PMID: 22293292.
started
completed
noticed a change
made it routine
▪ What to look for
A practical buying guide
Plain glycine powder is inexpensive and widely available. Look for a product that is simply glycine with no fillers or added sweeteners — it has a naturally mild sweet taste and dissolves easily in water. Capsule forms exist but reaching 3g means several capsules, so powder is usually more practical.
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▪ What to expect over time
Some people notice an easier time falling asleep the first night. Because the effect is thermoregulatory rather than something you build tolerance to, it tends to be consistent night to night rather than needing weeks to accumulate.
Side effects
Very well tolerated at 3g for most people. Mild loose stools or nausea can occur at higher doses. Regardless, always consult a care provider when adding or removing a supplement to your routine.
Who should be cautious
Theoretical interaction with clozapine due to NMDA modulation. At 3g, the dose is well below any toxicity threshold.
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Educational only. This is not medical advice. Always talk with a qualified clinician before changing medications, supplements, or care plans.