Magnesium glycinate: benefits, how much to take per day, side effects and the best time to take it

What magnesium glycinate is

A chelate is a mineral bound to amino acids. In magnesium supplements the amino acid is almost always glycine, so “magnesium chelate”, “magnesium glycinate” and “magnesium bisglycinate” on labels refer to the same form. In bisglycinate, one magnesium atom is bound to two glycine molecules.

Magnesium makes up about 14% of bisglycinate’s weight. That gives a simple conversion:

• 1,000 mg of bisglycinate contains about 140 mg of magnesium;
• 200 mg of magnesium needs about 1.4 g of bisglycinate;
• 200 mg of magnesium in this form comes with about 1.2 g of glycine.

So the dose is counted as elemental magnesium, not compound weight. A clear label reads: “Magnesium (as magnesium bisglycinate chelate) 200 mg”. For glycinate against citrate, oxide and malate, see types of magnesium compared.

Magnesium glycinate benefits

Magnesium helps turn food into energy and supports muscles, nerves and bones. The NHS says adults aged 19–64 need 300 mg a day (men) and 270 mg (women), and that most people can get this from a varied diet.

Glycinate is the usual pick when:

• citrate or oxide give you loose stools or stomach discomfort;
• you plan to take magnesium regularly and want predictable tolerability;
• an evening dose suits your routine;
• your diet is low in nuts, beans and wholegrains.

Check your diet before you buy. According to NIH ODS, 28 g of roasted pumpkin seeds provide about 156 mg of magnesium, 28 g of almonds 80 mg and half a cup of cooked spinach 78 mg. If foods like these are on your plate every day, you may not need a supplement.

What not to expect. Glycinate is often sold “for sleep and calm”. But the evidence that magnesium improves sleep in people who aren’t deficient is weak. And a usual glycinate dose contains less glycine than sleep studies used: they gave 3 g, about 2.5 times the glycine in 200 mg of magnesium as bisglycinate. Our article on glycine for sleep covers that evidence.

Buffered vs fully reacted magnesium glycinate

Pure bisglycinate is bulky: 200 mg of magnesium needs about 1.4 g of powder, which usually means several large capsules. So some brands add magnesium oxide. That fits more magnesium into each capsule and lowers the price. These products are called buffered.

That’s not a scam or poor quality, but there are trade-offs:

• oxide is more laxative, so a buffered product may be less gentle than you expect;
• less glycine for the same magnesium dose;
• cheaper per 100 mg of magnesium and fewer capsules a day.

Tap through a sample label to see how to spot it:

If you chose glycinate because of your gut, look for “magnesium bisglycinate chelate” alone in the brackets. If “magnesium oxide” appears there too, it’s buffered.

How much magnesium glycinate per day

• The usual dose is 100–200 mg of elemental magnesium a day.
• EFSA’s upper limit is 250 mg a day from supplements. The NHS says 400 mg or less is unlikely to cause harm, and that more than 400 mg for a short time can cause diarrhoea. Food magnesium doesn’t count.
• In pregnancy the US recommendation is 350–360 mg a day from all sources. Discuss any supplement with your midwife or GP.
• Count magnesium from multivitamins, ZMA, electrolyte drinks and effervescent tablets too.

The chart shows how much powder sits behind each dose, and why a glycinate capsule can’t stand in for glycine at bedtime:

Best time to take magnesium glycinate

There’s no convincing evidence that morning or evening doses are absorbed better. Practical rules:

• take it with food to reduce nausea;
• split doses above 200 mg into two;
• an evening dose with dinner works well if you link magnesium to your sleep routine;
• keep it apart from medicines: antibiotics, bisphosphonates and levothyroxine are taken separately.

If you also take glycine or another sleep aid in the evening, start one supplement at a time so you know what’s working. Melatonin is prescription-only in the UK. Our sleep and stress section covers the better-studied options.

Magnesium glycinate side effects

Side effects are the same as for other magnesium supplements: loose stools, nausea and stomach cramps. NIH ODS links diarrhoea most often with magnesium carbonate, chloride, gluconate and oxide. Glycinate isn’t on that list, but large single doses and buffered products can still loosen stools.

Serious magnesium excess is rare and usually linked to very large doses of laxatives or antacids, or to kidney disease. Signs include nausea and vomiting, weakness, low blood pressure and an irregular heartbeat. If you notice them, stop taking it and get medical advice.

Who should avoid it and interactions

• Kidney disease. Kidneys clear excess magnesium; if they don’t work well, it builds up. Only under medical supervision.
• Tetracycline and quinolone antibiotics. Take the antibiotic at least 2 hours before or 4–6 hours after magnesium.
• Bisphosphonates. Separate by at least 2 hours.
• Pregnancy and breastfeeding. Check with your GP or midwife.
• Children. Doses depend on age and weight; follow a paediatrician.

Magnesium with added B6 is a separate case, because the B6 dose is the main limit: see magnesium and vitamin B6. If price matters more and your gut is fine, consider magnesium citrate.

How to choose magnesium glycinate on iHerb

1. Find elemental magnesium per serving in the Supplement Facts and check how many capsules make that serving.
2. Read the form in brackets. “Magnesium bisglycinate chelate” alone means pure chelate; “magnesium oxide” alongside means buffered.
3. Choose a strength that gives 100–200 mg of magnesium a day.
4. Compare the price per 100 mg of elemental magnesium in £ or €, not per bottle.
5. Prefer products with independent quality testing (USP, NSF or similar seals).

Our Supplement Facts guide covers label reading in detail. Not sure you’re short of magnesium? Start with magnesium deficiency symptoms.