Glycine 101: Benefits, Dosage and How to Use It

The Short Answer

Glycine is the simplest amino acid there is, and one of the most useful. Your body uses it to build collagen, make glutathione (one of its main antioxidants) and calm the nervous system.

Its best-studied use is sleep. In several small studies, 3g of glycine taken before bed helped people fall asleep faster, sleep better and feel less tired the next day. Most people take 3–5g a day, it's very well tolerated, and it has a mildly sweet taste that disappears into water or tea.

That's the quick version. Below we'll go through the science, what the research does and doesn't show, how much to take, and the best way to use it.

What Is Glycine?

Glycine is an amino acid, one of the building blocks of protein. It's the smallest of them all, which is exactly what makes it so useful: it fits into tight spots other amino acids can't.

It's "conditionally essential". Your body can make glycine, so it's not classed as essential. But researchers have questioned whether it can make enough. One analysis estimated that an average adult makes about 3g a day and gets another 1.5–3g from food, while collagen production alone needs around 12g. That leaves a theoretical shortfall of about 10g a day (Meléndez-Hevia et al., 2009). It's a calculation rather than a measured deficiency, but it's why glycine is called conditionally essential.

What your body uses it for:

• Collagen. Glycine makes up one third of the amino acids in collagen, the protein that holds your skin, tendons, ligaments and bones together (Meléndez-Hevia et al., 2009).
• Glutathione. Along with cysteine and glutamate, glycine is one of the three amino acids your body uses to make glutathione, a key antioxidant.
• Creatine. Glycine is one of the raw materials your body uses to make its own creatine.
• Calming signals. In the brainstem and spinal cord, glycine works as an inhibitory neurotransmitter, a chemical messenger that quietens nerve activity.

Where it comes from in food: the richest sources are collagen-heavy foods like gelatin, bone broth, and the skin and connective tissue of meat. Lean cuts of meat, eggs and plant foods contain much less. If your diet is mostly lean meat, chicken breast and eggs, you're not getting much glycine from food.

Glycine Benefits, Ranked by Evidence

You'll see glycine linked to a long list of benefits online. Here's what the research actually supports, from strongest to most preliminary.

Sleep

This is where the evidence is strongest. In a Japanese study of people with ongoing sleep complaints, 3g of glycine before bed improved how well people felt they slept, and sleep lab measurements showed they fell asleep faster and reached deep (slow-wave) sleep sooner. They were also less sleepy and did better on memory tasks the next day. Importantly, it didn't change the structure of their sleep the way many sleeping pills do (Yamadera et al., 2007).

In another study, men whose sleep was cut back to about 5.5 hours a night took 3g of glycine before bed. They reported less fatigue and had faster reaction times the next day than when they took a placebo (Bannai et al., 2012).

How it seems to work: animal research suggests glycine acts on the brain's master clock, widening blood vessels in the hands and feet so heat escapes and core body temperature drops. That fall in core temperature is one of the body's natural signals that it's time to sleep (Bannai et al., 2012).

The catch: these studies were small, and several came from the same research group. The results are consistent and encouraging, but glycine is a gentle sleep aid, not a knockout pill.

Glutathione and healthy ageing

Glutathione levels tend to fall with age. Researchers at Baylor College of Medicine gave older adults a combination of glycine and N-acetylcysteine (NAC), known as GlyNAC, for 16 weeks. Compared with placebo, it corrected their glutathione deficiency, lowered oxidative stress and improved muscle strength, walking speed, waist size and blood pressure (Baylor College of Medicine). It's exciting research, but most of it comes from one group, and it was done in older adults.

Blood sugar

In a small 2002 study, nine healthy adults drank glucose with and without glycine. With glycine, their blood sugar response was more than 50% lower (Gannon et al., 2002). That's an interesting single-dose result, not evidence that glycine manages blood sugar day to day.

Collagen, skin and joints

Because glycine is such a big part of collagen, it's often sold for skin and joint health. The logic is sound, but there's very little research testing glycine on its own for skin or joints. If that's your main goal, hydrolysed collagen peptides have far more direct research behind them.

How Much Glycine Should You Take?

There's no official recommended dose for glycine, so these figures come from the doses used in research and common practice.

Start with 3g. That's the dose used in the sleep studies, and it's plenty for most people. If you feel no difference after a week or two, you can move up to 5g.

More isn't necessarily better. Much larger doses have been used in medical research, but there's no evidence that going beyond a few grams adds anything for sleep, and big doses are more likely to upset your stomach.

The Best Way to Use Glycine

For sleep, make it part of your wind-down. Stir 3g into a glass of water or a cup of caffeine-free tea 30–60 minutes before bed. Glycine tastes slightly sweet (its name comes from the Greek word for sweet), so many people use it in place of honey in their evening tea.

Give it a fair trial. The sleep studies measured effects from the first nights, so you'll know fairly quickly whether it helps you. Try it consistently for a week or two before you decide.

Don't skip the basics. Glycine works best on top of good sleep habits, not instead of them. A consistent wake-up time, a caffeine cut-off and a cool, dark room still do most of the heavy lifting. We cover these in Part 4 of our weight loss guide.

Pair it with NAC for glutathione. Glycine and N-acetylcysteine are the two building blocks behind the GlyNAC research. You can take them separately or as a combined GlyNAC powder.

Glycine or collagen? They do different jobs. Collagen gives you glycine plus other amino acids and peptides linked to skin and joint benefits. Glycine on its own gives you a precise, sleep-sized dose without the extra protein. Plenty of people take both: collagen in the morning, glycine at night. See our Collagen Peptides 101 guide for more.

It mixes with almost anything. Glycine dissolves easily, so you can also add it to a protein shake, smoothie or post-workout drink.

Is Glycine Safe? Side Effects and Who Should Check First

Glycine is a normal part of the food you eat, and at a few grams a day it's very well tolerated. The most common complaint is an upset stomach, nausea or vomiting, and even that is rare and goes away when people stop taking it (WebMD).

That said, long-term safety hasn't been studied in depth, and some people should talk to their doctor before taking it (WebMD):

• Anyone taking clozapine. People on this antipsychotic medication should avoid glycine.
• Anyone who has had a stroke. Only take glycine under a doctor's supervision.
• Pregnant or breastfeeding women, and children. There isn't enough safety research, so extra caution is needed.

We'd also suggest checking with your healthcare provider first if you have kidney or liver disease or another existing health condition, or if you take prescription sleep medication.

And one important point: glycine isn't a treatment for insomnia. If you're regularly struggling to sleep, see your GP. Ongoing poor sleep can have causes, like sleep apnoea, that need proper diagnosis.

Focal Nutrition Glycine Powder

We kept our glycine simple: pure glycine powder, third-party tested, with a measuring scoop in every pack.

How to use it: mix 1.5–2 scoops (5g) into 200–300ml of water or your drink of choice, 30–60 minutes before bed. For the 3g sleep dose from the research, use roughly one scoop.

The 300g pack is an easy way to see whether glycine helps your sleep. If it does, the 1kg bag is the better buy for nightly use.

Shop Focal Nutrition Glycine Powder

Want glycine and NAC in one scoop? Try our GlyNAC powder. Glycine is also part of our Health & Longevity Bundle.

Glycine FAQ

Does glycine make you sleepy?

Not in the way a sleeping pill does. Research suggests it helps your core body temperature drop, which is one of your body's natural cues for sleep. In studies, people taking 3g before bed fell asleep faster and felt less sleepy the next day.

When is the best time to take glycine?

For sleep, 30–60 minutes before bed. For other goals, timing doesn't seem to matter much, so take it whenever suits you.

Can I take glycine every night?

The sleep studies used it nightly, and at a few grams a day glycine is very well tolerated. Long-term research is limited, so if you have a health condition or take medication, check with your doctor first.

Is glycine the same as magnesium glycinate?

No. Magnesium glycinate is magnesium bound to glycine, and it's taken for the magnesium. A typical dose provides some glycine, but usually less than the 3g used in the sleep research.

Can I take glycine with creatine or protein powder?

Yes. There are no known problems combining them, and glycine mixes easily into a shake. In fact, glycine is one of the building blocks your body uses to make its own creatine.

Does glycine have side effects?

Side effects are rare. The most common is an upset stomach. People taking clozapine should avoid glycine, and anyone who is pregnant, breastfeeding or managing a health condition should check with their doctor first.

General information only, not medical advice. Supplements are not a substitute for a balanced diet. Check with your GP or pharmacist before taking glycine if you have a health condition, take medication, or are pregnant or breastfeeding.