Compare magnesium supplements on what you actually get: the amount of magnesium per daily dose, the form (glycinate, citrate, malate and others) and the cost per 100mg. The NHS says 400mg or less a day from supplements is unlikely to cause harm, so we show you how to read the label before you buy.
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How much magnesium do you need a day?
The NHS says adults aged 19 to 64 need 300mg of magnesium a day for men and 270mg a day for women, and that having 400mg or less a day of magnesium from supplements is unlikely to cause any harm.
Magnesium is found in a wide variety of foods, including spinach, nuts and wholemeal bread, so a supplement adds to what you already get from your diet rather than replacing it.
What does the mg on a magnesium label mean?
The figure that matters is the amount of magnesium itself (sometimes called elemental magnesium) per daily dose, which is what the nutrition table and %NRV refer to. A headline such as "1,000mg magnesium citrate" is the weight of the whole compound, and only part of that is magnesium.
%NRV (Nutrient Reference Value) compares the amount with a standard reference. The NRV for magnesium is 375mg, so 100% NRV is slightly under the NHS 400mg supplement figure.
| Magnesium per daily dose | %NRV | How it compares with NHS advice |
|---|---|---|
| 100mg | 27% | About a third of the daily amount for men |
| 200mg | 53% | Two thirds of the daily amount for men |
| 270mg | 72% | The daily amount for women aged 19 to 64 |
| 300mg | 80% | The daily amount for men aged 19 to 64 |
| 400mg | 107% | The most the NHS says is unlikely to cause harm from supplements |
"We want customers to understand what they're taking rather than simply choosing the highest numbers on the label," says Andy Arshad, who runs SupplementHQ. Our guide to reading a supplement label explains %NRV in more detail.
Magnesium glycinate, citrate or oxide: what's the difference?
They are different magnesium compounds, and they differ in how well they dissolve, how well they're absorbed and how much they cost. The US National Institutes of Health says the aspartate, citrate, lactate and chloride forms tend to have higher bioavailability than the oxide and sulfate forms (bioavailability means how much of it your body absorbs and uses), based on small studies. It does not assess glycinate.
"Magnesium oxide, citrate and glycinate are often sold under the same general category, but they differ in absorption, tolerability and price," says Andy. In this collection you'll find magnesium bisglycinate (glycinate), citrate, malate and L-threonate, plus liquids, gummies, oil sprays and a body lotion. Compare the magnesium per daily dose first, then the form.
What is magnesium glycinate?
Magnesium glycinate, also sold as bisglycinate, is magnesium bound to the amino acid glycine. It is one of the most searched forms, and it is often more expensive per milligram of magnesium than citrate.
Because glycine makes up much of the weight of the compound, a glycinate capsule can contain less magnesium than its size suggests. Check the nutrition table for the magnesium per daily dose, and don't assume a higher price means more magnesium.
Does magnesium help you sleep?
There is no authorised health claim linking magnesium to sleep, so we don't make one. "Magnesium for sleep" is a very common search, and some products in this collection are named around relaxation or calm, but the name of a product is not evidence.
The claims that are authorised, where a product is at least a source of magnesium, include "Magnesium contributes to a reduction of tiredness and fatigue", "Magnesium contributes to normal functioning of the nervous system", "Magnesium contributes to normal psychological function" and "Magnesium contributes to normal muscle function". If you have ongoing sleep problems, speak to your GP or pharmacist. Browse sleep & relaxation.
What are the side effects of too much magnesium?
The NHS says taking high doses of magnesium (more than 400mg) for a short time can cause diarrhoea. The NIH notes that the forms most commonly reported to cause diarrhoea are magnesium carbonate, chloride, gluconate and oxide.
The easiest way to go over 400mg is to take more than one product. Magnesium also appears in multivitamins, ZMB-style zinc and magnesium products, and some electrolyte drinks, so add up the amount across everything you take. Speak to your GP or pharmacist first if you have kidney problems, another medical condition or take medication.
Magnesium with zinc, B6 or vitamin D?
Combination products are convenient, but check each ingredient against its own limit. The NHS says not to take more than 10mg of vitamin B6 a day in supplements unless advised to by a doctor, and not to take more than 25mg of zinc supplements a day unless advised to by a doctor.
We stock magnesium with B6, with zinc, and with vitamin D3 and K2. See also zinc supplements and vitamin D.
How do you compare value on magnesium supplements?
Work out the cost per 100mg of magnesium, not the cost per tub. Capsule counts, serving sizes and the amount of magnesium per capsule all vary.
How to compare value (example figures, not real products): a £15 tub of 90 glycinate capsules, three a day for 300mg of magnesium, lasts 30 days and costs 50p a day, or about 17p per 100mg. A £9 tub of 60 citrate tablets, one a day for 150mg, lasts 60 days and costs 15p a day, or 10p per 100mg.
"Two products that look almost identical on the shelf can offer different value," says Andy.
Which is the best magnesium supplement?
The best one for you gives the amount of magnesium you're looking for, in a form you tolerate, at a sensible cost per 100mg, without taking you over 400mg a day from supplements.
Start with the magnesium per daily dose, then the form, then the cost. If you're unsure whether you need one at all, our guide to what supplements you actually need is a good place to start, or go back to all vitamins & supplements.
We sell the products on this page. That's our commercial interest, and it's why we show the evidence alongside them. This page is general information for adults, not personalised medical advice. Food supplements should not replace a varied, balanced diet.
Written by Andy Arshad, SupplementHQ. Last reviewed 11 October 2026.