Types of magnesium compared: glycinate vs citrate, how much to take and the best supplement for you

What magnesium does and who needs more

Hundreds of enzymes rely on magnesium. Your muscles and nerves need it, and so do energy metabolism and protein synthesis. The NHS puts the daily need at 300 mg for men and 270 mg for women. Nuts, seeds, beans, wholegrains and leafy greens are the richest sources.

You’re more likely to fall short if:

• Your diet is low in nuts, beans and wholegrains.
• You’ve taken proton pump inhibitors (omeprazole and similar) or diuretics for a long time.
• You have type 2 diabetes or a gut condition, or you drink heavily.
• You’re over 65.

A blood test says little about your stores. Almost all magnesium sits in bone and cells, and the body holds the blood level steady until late. So decisions usually rest on your diet, symptoms and medical advice, not on one number. Signs and food sources are covered in our guide to magnesium deficiency symptoms.

Magnesium for leg cramps. Night cramps send more people to the supplement aisle than almost anything else, but the evidence doesn’t back magnesium for them. A 2020 Cochrane review (11 trials, 735 people) found magnesium unlikely to give older adults meaningful protection from ordinary night cramps. In pregnancy the results conflict. If cramps are frequent or severe, or started after a new medicine, see your GP rather than raising the dose.

Types of magnesium compared

The forms differ mainly in two things: how well your gut tolerates them and how much of their weight is actual magnesium. Human absorption studies are few and small. Tolerability is the more practical guide.

Elemental magnesium is the number that matters. That’s why “magnesium glycinate 1000 mg” in big print doesn’t mean 1,000 mg of magnesium. A serving like that holds about 140 mg, a seventh of the headline figure. Good labels list elemental magnesium and give the form in brackets: “Magnesium (as magnesium bisglycinate chelate) 200 mg”.

Glycinate: the gentle option

This is magnesium bound to the amino acid glycine. It’s the usual pick for evening use and for people whose stomach reacts to other forms. Watch for “buffered” on the label. Buffered glycinate has magnesium oxide added to raise the magnesium per capsule. That’s fine, but it’s more likely to loosen stools. Doses, timing and side effects are covered in our magnesium glycinate guide.

Citrate: affordable and soluble

Citrate dissolves well in water and comes as capsules, tablets and powders. It’s a sensible choice if you don’t need glycinate for tolerability. If it loosens your stools, lower the single dose. More on its use for constipation in our magnesium citrate guide.

Magnesium glycinate vs citrate: which should you take?

Both are well absorbed. There’s no solid evidence that one gets into the body better than the other. The difference is in how they feel:

Choose glycinate if other forms upset your stomach. Choose citrate if price matters or a mild laxative effect would suit you. Oxide vs citrate is a simpler call: oxide is cheaper per milligram but harder on the gut.

Oxide: lots of magnesium, not for everyone

Oxide packs the most magnesium into one tablet and costs the least. But much of it isn’t absorbed and stays in the gut. That’s why it often works as a mild laxative.

Threonate, malate, taurate

These are niche forms. L-threonate drew interest because it raised brain magnesium in animal studies. Convincing human data is scarce, and it costs several times more. Malate and taurate are well tolerated but have no proven advantage over glycinate.

How much magnesium per day

Start with how much you already get from food. If you eat nuts, beans and wholegrains most days, you may not need a supplement at all.

• A typical supplement dose is 100–200 mg of elemental magnesium a day.
• EFSA sets 250 mg a day as the limit for supplements. The NHS says 400 mg or less is unlikely to cause harm, and the US limit is 350 mg. Magnesium from food doesn’t count towards any of them.
• Take it with food, and split doses above 200 mg into two to spare your gut.
• Timing has little effect on absorption. Glycinate is often taken in the evening, citrate earlier in the day.

Count every source. Magnesium also turns up in multivitamins, ZMA, electrolyte mixes and fizzy tablets. Products that pair it with B6 add a second nutrient with its own limit, explained in our magnesium and vitamin B6 guide.

If the tub only gives the compound weight, work it out yourself: pick the form and type in the milligrams from the label.

Is magnesium good for sleep?

Glycinate is the usual pick for sleep. It’s gentle, and glycine itself has been studied for sleep. Overall, though, the evidence for magnesium is modest. A 2021 systematic review in older adults with insomnia found only a small cut in the time it took to fall asleep, and the studies were of low quality. If you’re not low in magnesium, don’t expect much.

If poor sleep has lasted more than three months, the first-line treatment is cognitive behavioural therapy for insomnia (CBT-I). Ask your GP about it. For other options, see our guide to sleep supplements.

Side effects, who should avoid it and interactions

• Kidney disease. Your kidneys clear excess magnesium. When they don’t work well, it can build up. Take it only under medical supervision.
• Tetracycline and quinolone antibiotics (doxycycline, ciprofloxacin and others). Magnesium blocks their absorption. Take the antibiotic at least 2 hours before or 4–6 hours after magnesium.
• Bisphosphonates for osteoporosis. Keep at least 2 hours apart.
• Levothyroxine for the thyroid. Minerals reduce its absorption, so separate by 4 hours.

In practice, start from the medicine: note when you take it, then move magnesium the right number of hours away.

In pregnancy, check with your midwife or GP before you start. Nausea, severe diarrhoea, weakness or an irregular heartbeat mean you should stop and see a doctor. Which supplements clash with each other is shown in our vitamin compatibility chart.

How to choose the best magnesium supplement in the UK

1. Pick the form: glycinate for a sensitive gut, citrate as an all-rounder.
2. Check elemental magnesium per serving and how many capsules make that serving. It’s often 2–4 capsules.
3. Compare the price per 100 mg of elemental magnesium, not per bottle.
4. Prefer products with independent testing (USP, NSF and similar seals).
5. Before you order, check iHerb delivery to the UK and any import charges.

More on reading labels in our Supplement Facts guide.