Can glycine help you sleep better?

It might, for some people, and it is one of the gentler things you can try. But the research is still small, so I want you to know exactly what it shows before you spend money on it.

What glycine is

Glycine is an amino acid, one of the building blocks of protein. Your body makes it, and you also get it from protein-rich foods. It also works as a messenger in your nervous system, which is why researchers have looked at it for sleep. [1]

What the research found

Researchers in Japan reported that taking glycine before bed improved how well people with poor sleep felt they had slept. [1]

In a follow-up study, healthy volunteers had their sleep cut by a quarter for three nights. Before bed they took either 3 g of glycine or a dummy powder. The next day, the glycine group felt less tired, tended to feel less sleepy and reacted faster on a computer test. [2]

Animal research hints at why: glycine increased blood flow to the skin and lowered core body temperature, which is something that naturally happens as you fall asleep. [3]

Keep it in perspective

These studies were small, and they were run by researchers working for a company that makes glycine. They need confirming by independent teams. Glycine is not a treatment for insomnia, and no glycine product is allowed to claim it improves sleep.

With clients, I always fix the basics first: a regular bedtime, a dark and cool bedroom, less caffeine after lunch and less alcohol. If sleep is still poor after that, glycine is a low-risk thing to test for a couple of weeks.

How to take glycine

  • Research dose: the studies used 3 g taken shortly before bed. [2]
  • Check the label: capsules are often 1,000 mg each, so that would be three capsules. Follow the product instructions.
  • Judge it fairly: keep a simple note of how you sleep and feel for two weeks, so you know whether it is worth continuing.

Who should check with their GP first

Glycine was well tolerated in these studies, but check with your GP or pharmacist first if you take medication that affects the brain or sleep, such as antipsychotics, or if you are pregnant or breastfeeding. Ongoing poor sleep is always worth discussing with your GP.

Frequently asked questions

How much glycine should I take for sleep?

The human studies used 3 g of glycine taken shortly before bedtime. With 1,000 mg capsules, that is three capsules; follow the product label.

When should I take glycine?

In the research it was taken shortly before bed.

Does glycine work for sleep?

Small studies reported better subjective sleep quality and less next-day fatigue after restricted sleep. They were run by researchers working for a glycine producer and need independent confirmation.

Is glycine a sleeping pill?

No. Glycine is an amino acid, not a medicine, and no glycine product is authorised to claim it improves sleep. Persistent poor sleep is worth discussing with your GP.

Related reading: Magnesium for sleep and recovery, L-theanine for stress and sleep, Ashwagandha for stress and sleep.

Make it part of a plan

Better sleep usually comes from training, nutrition and routine working together. If you want training and nutrition built around you, online coaching includes nutrition and supplementation guidance. Apply for coaching and tell me what you are working on.

This article is general information, not medical advice. If you take medication, are pregnant or breastfeeding, or have a medical condition, check with your GP or pharmacist before starting a supplement.

Evidence reviewed: October 2026. This guide covers the human studies on glycine and sleep, their limits and how to try it sensibly.

Research and further reading

  1. Bannai and Kawai (2012). New therapeutic strategy for amino acid medicine: glycine improves the quality of sleep. J Pharmacol Sci.
  2. Bannai et al. (2012). The effects of glycine on subjective daytime performance in partially sleep-restricted healthy volunteers. Front Neurol.
  3. Kawai et al. (2015). The sleep-promoting and hypothermic effects of glycine are mediated by NMDA receptors in the suprachiasmatic nucleus. Neuropsychopharmacology.