Glycine for Sleep: Does It Work, How Much and When to Take It

Glycine for sleep: which option fits your routine?

For the 3g trial dose you need pure glycine. How the options compare (checked October 2026):

Option	Format	How people use it	What to know
Magnesium Glycinate Sleep Complex	Berry drink powder, 4.75g scoop	In a hot or cold drink, 30 minutes before bed	290mg magnesium, which contributes to a reduction of tiredness and fatigue. Contains glycine, amount not stated
Pure glycine powder (we don’t sell it)	Plain powder or capsules	3g in water before bed	Glycine as the only ingredient, grams per scoop stated. “L-glycine” is the same thing
Sleep CBD Oil with Passion Flower	Oil, 500mg (5%) or 1,000mg (10%)	Drops under the tongue as part of a wind-down	Broad spectrum CBD with passion flower. About 4 drops (500mg) or 2 (1,000mg) for 10mg

The FSA’s 10mg a day figure is precautionary advice rather than a legal limit, set while longer-term safety research continues. At Evopure we think it is a very cautious figure, and many adults use more. If you go above it, increase slowly, and check with your GP or pharmacist first if you take any medication.

Value: the 1,000mg Sleep CBD Oil costs less per mg than the 500mg. Subscribe and Save lowers every order; skip, pause or cancel any time.

What you get with Evopure:

• CBD products only: every batch of our CBD oils and capsules is third-party tested at ISO 17025 labs, with reports on request (lab testing).
• Our CBD is broad spectrum and THC free, on each batch report, and on the FSA public list, linked to validated applications.
• All made in the UK, vegan and alcohol-free.
• Tracked Royal Mail delivery, same-day dispatch before 3pm Monday to Thursday (delivery). Unopened, unused items returnable within 14 days (returns).

They’re food supplements, not medicines, and we don’t claim they improve sleep. Choose the Magnesium Glycinate Sleep Complex for an evening drink, or Sleep CBD Oil for drops.

What is glycine?

Glycine is the smallest amino acid. Your body makes it, and you also get it from protein foods, especially collagen and gelatine. In the brain and spinal cord it works as a signalling molecule, which is why researchers became interested in it for sleep.

The leading idea, mostly from rat studies, is that glycine nudges blood flow towards the skin, so core body temperature drops slightly. A small fall in core temperature is part of how the body normally winds down for sleep. In rats, this effect ran through the brain’s body clock (the suprachiasmatic nucleus). Whether the same happens in people at a 3g dose isn’t proven.

Does glycine help you sleep?

Possibly, a little, for some people. The human evidence comes down to three small trials, all using about 3g before bed:

That is a very small evidence base. A 2026 scoping review that searched the main medical databases found only these three glycine sleep trials. All three reported a benefit on at least one sleep-related measure, but the authors called for larger trials.

Things to weigh up:

• Tiny numbers. The 2012 study analysed just seven men.
• Short. Days, not months.
• Industry links. Much of the research was run by scientists at Ajinomoto, a Japanese amino acid company. That doesn’t make it wrong, but independent trials are missing.
• Mostly how people felt. Many results are self-rated, which placebo can sway.

Our honest take: glycine is a reasonable, low-cost thing to try alongside good sleep hygiene, not instead of it. For how it stacks up against other options, see natural sleep aids ranked by evidence.

How much glycine for sleep?

The studies used 3g. There is no evidence that more, such as 5g, works better.

If you try it, start at 3g or below, give it a week or two and judge honestly whether your sleep or mornings feel any different. A simple sleep calculator or diary helps here.

How long before bed should you take glycine?

The 2012 trial gave 3g about 30 minutes before bedtime, the others just say before bed. In practice, 30 to 60 minutes before bed, at the same time each night, fits how it was tested. For more on timing, see how to fall asleep fast.

Glycine side effects and who should avoid it

Glycine was generally well tolerated in the sleep studies, and the 2012 trial reported no side effects. But the trials were tiny and short, so long-term safety at supplement doses isn’t well studied. If you get stomach upset, stop.

• Clozapine: don’t take glycine unless your psychiatrist agrees. In a small 1999 trial, high-dose glycine seemed to blunt clozapine’s effect.
• If you take any other prescribed medicines, or have a kidney, liver or mental health condition, check with your GP or pharmacist first.
• There isn’t enough evidence on glycine supplements in pregnancy or breastfeeding. We don’t recommend our products during pregnancy or breastfeeding.
• Supplements are for adults (18+) only.

The NHS advises seeing a GP if changing your sleep habits hasn’t helped, you’ve had trouble sleeping for months, or it’s making daily life hard to cope with. Loud snoring with pauses in breathing, or waking unrefreshed every day, also needs checking. See insomnia and why you wake up tired.

Glycine vs magnesium glycinate

They are not the same thing. Magnesium glycinate (also called bisglycinate; see glycinate vs bisglycinate) is magnesium bound to two glycine molecules. It is mainly a way of taking magnesium, and the glycine it carries is small next to the 3g used in sleep studies.

The maths: magnesium is about 14% of magnesium bisglycinate by weight (PubChem molecular weight 172.42), so each 100mg of magnesium from bisglycinate comes with roughly 0.6g of glycine. Even 400mg of magnesium, the most the NHS says is unlikely to cause harm from supplements, would supply only about 2.5g. Approximate, assuming fully reacted bisglycinate.

How much glycine is in our Magnesium Glycinate Sleep Complex? The label lists glycine without an amount. Its 290mg of magnesium comes from bisglycinate and citrate, so the bound glycine is under about 0.9g, and the added glycine is listed after both magnesium compounds (UK labels list ingredients by weight). That’s well under 3g: an evening drink, not a trial dose.

Magnesium contributes to normal functioning of the nervous system and normal psychological function. For whether magnesium itself helps sleep, see magnesium for sleep, and for timing, the best time to take magnesium. Comparing forms? Read glycinate vs citrate vs threonate. For the other ingredients, see L-theanine and passionflower for sleep.

Some people take glycine and magnesium together. There is no research on the combination for sleep, so treat it as personal experiment rather than evidence.

Food sources of glycine

Most people already get a few grams of glycine a day from food. The richest sources are collagen-rich foods:

• Gelatine: about 19g of glycine per 100g of dry powder in USDA data, so a 10g spoonful has roughly 1.9g.
• Bone broth and slow-cooked cuts with skin and connective tissue.
• Meat and poultry: roast chicken breast has about 1.5g per 100g.
• Fish: cooked farmed salmon has about 1g per 100g.

Food alone rarely gets you a concentrated 3g at bedtime, which is why the studies used powder. If you’re comparing other bedtime options, see sleep capsules, melatonin in the UK and the best teas for sleep.

Does glycine break a fast?

Strictly, yes. Glycine is an amino acid, which UK labels count as protein at 4kcal per gram, so 3g is about 12 calories. That breaks a water-only or religious fast. For time-restricted eating there’s no research on glycine, so it comes down to your own rules.

Is glycine legal and safe in the UK?

Yes. Glycine is sold as a food supplement and is an approved UK food additive (E640). It isn’t a medicine and has no authorised health claims. 3g was well tolerated in the trials, but follow the cautions above.

Related guides: GABA supplement, deep sleep, tryptophan for sleep, collagen supplements, magnesium for anxiety, powder vs tablets, threonate, best magnesium supplement UK, how long magnesium takes and the best magnesium drinks.