Glycine for sleep and blood sugar

1. Does glycine help you sleep?

There is a signal. It rests on very few people.

Glycine is an amino acid, one of the building blocks of protein. Your body makes it, and you also get it from protein foods such as meat, fish and gelatin. In the brain it acts as a calming messenger.

The best summary is a 2024 systematic review in GeroScience. It found three sleep trials in healthy adults, all using 3 g of glycine taken shortly before bed.

• People rated their sleep better. Each trial reported better sleep quality or less daytime tiredness.
• One trial wired people up. In the 2007 study, sleep recordings showed people fell asleep faster and reached deep sleep sooner.
• The trials were tiny and short. Between 10 and 19 people each, lasting two to four nights.

The reviewers judged these studies to have small samples and a high risk of bias. One more detail matters. The lead author of the 2012 trial worked at Ajinomoto, a Japanese amino acid manufacturer.

So glycine may help a rough night or two. Nobody has tested whether it still works after months of nightly use.

2. Does glycine lower blood sugar?

Two studies point that way. Neither settles it.

The first is a 2002 study in the American Journal of Clinical Nutrition. Nine healthy adults drank 25 g of glucose, with or without glycine. With glycine, the rise in blood sugar was more than 50% smaller.

That is a striking number from one drink in nine people. The dose was matched to lean body mass, which works out at roughly 3.5 to 5 g for most adults.

The second is a 2008 trial in 74 people with type 2 diabetes. After three months, HbA1c was significantly lower in the glycine group than the placebo group. HbA1c is your average blood sugar over roughly three months.

Two cautions apply. That trial used several doses a day, well above the 3 g sleep dose, and it studied people with diabetes. If your blood sugar is already normal, you have much less room to move.

3. How would you know if it works for you?

Test first, give it twelve weeks, then test again.

For blood sugar, the marker is HbA1c. It ignores the daily swings a finger-prick glucose reading picks up. Below 42 mmol/mol is normal, 42 to 47 is pre-diabetes, and 48 or above is in the diabetes range.

Our Advanced Heart Health panel (£159) measures HbA1c alongside hs-CRP, a sensitive marker of inflammation, and the full cholesterol breakdown. Fasting glucose and fasting insulin are not in our home kits. Those need a vein sample, so raise them with your GP.

Sleep is harder to put a number on. Keep a simple diary for two weeks before you start and two weeks after. If you are still exhausted, the cause may sit somewhere glycine cannot reach.

Our General Energy & Wellness panel (£149) checks cortisol, magnesium, thyroid, vitamin D and B12. Cortisol is your main stress hormone, and it is closely tied to sleep. Both panels use a home finger-prick kit, with results usually within 5 working days of the lab receiving your sample.

Poor sleep that drags on deserves more than a supplement. The NHS is clear on when to get help.

4. Is glycine safe to take every night?

At the doses in these studies, it appears to be well tolerated.

The 2024 review called glycine “likely safe” as an oral supplement. Supervised psychiatric trials have gone far higher. One study gave 60 g a day for eight weeks without people getting clinically worse.

• Check your medicines first. Speak to a pharmacist if you take anything for blood sugar or mental health.
• Magnesium glycinate is not a glycine dose. 200 mg of magnesium as glycinate carries about 1.2 g of glycine, well under the 3 g in the trials.
• More is not better. The sleep trials used 3 g, not a scoop.

If you already take magnesium for sleep, our guide to magnesium glycinate that is not working covers what to check next.

Never stop or change a prescribed medicine because of a supplement. That is a conversation for a qualified clinician.

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