Independent supplement ratingsUS and Canada · Updated weekly
A ratings desk for a category that has spent thirty years grading its own homework.
A ratings desk for a category that has spent thirty years grading its own homework.
The daily target is 310 to 420 mg depending on who you are, most people miss it, and the number on the front of the tub is not the number that counts.
The short answer: adults need roughly 310–420 mg of elemental magnesium a day, from food and supplements together — 400 mg for men under 31 and 420 mg after, 310 mg for women under 31 and 320 mg after. Most people fall short. And the figure printed largest on a magnesium bottle is usually not the figure that matters.
| Who | Daily target (elemental Mg) |
|---|---|
| Men, 19–30 | 400 mg |
| Men, 31 and over | 420 mg |
| Women, 19–30 | 310 mg |
| Women, 31 and over | 320 mg |
That is the total for the day, not the amount to take as a pill. Our magnesium calculator gives you the figure for your age and sex, plus a sensible top-up.
This is the part that makes magnesium worth talking about at all, because plenty of supplements solve a problem nobody has. A 2025 review of global intake data puts it plainly: national nutrition surveys consistently document inadequate intake against these targets, and an estimated 2.4 billion people, roughly three in ten, fall below the recommended level. (Zhang et al., 2025)
Magnesium is concentrated in foods a lot of people eat rarely: pumpkin seeds, almonds, spinach, black beans, whole grains. Refining grain strips most of it out. So a diet built on refined carbohydrate and meat can be adequate in protein and still land well under the number above.
Here is where the category gets slippery. A capsule labelled "Magnesium Citrate 1,000 mg" does not contain 1,000 mg of magnesium. It contains 1,000 mg of magnesium citrate — a compound in which magnesium is a minority partner. The number you need is the elemental magnesium, and it is usually printed smaller, or in the Supplement Facts panel, or not at all.
The share of elemental magnesium differs by form, which is why two products with identical front-of-pack numbers can deliver very different doses. Our forms guide works through that arithmetic, and every product in our magnesium ranking is scored on its elemental figure rather than its compound weight.
Then there is absorption. Magnesium oxide carries a high proportion of elemental magnesium and the body absorbs comparatively little of it; chelated forms such as glycinate carry less on paper and deliver more in practice. This is exactly why the cheapest magnesium per gram in our rankings is not the one we rank first.
If you are topping up rather than treating something, 200–300 mg of elemental magnesium a day is the sensible range, and it is what most clinical trials use.
There is a ceiling worth knowing. The tolerable upper intake level applies to supplemental magnesium and sits at 350 mg a day — not because more is toxic, but because magnesium salts draw water into the bowel. Past that point the usual outcome is loose stools, and it arrives faster with oxide and citrate than with glycinate. Magnesium from food carries no such limit: your kidneys handle the excess.
The exception that matters: if you have reduced kidney function, magnesium clearance is impaired and supplementing is a conversation for your doctor, not a decision for a website.
For sleep, the honest answer has recently got better. A 2025 randomised, double-blind, placebo-controlled trial gave 155 adults with self-reported poor sleep 250 mg of elemental magnesium as bisglycinate or a placebo. By week four the magnesium group's Insomnia Severity Index scores had fallen further than placebo — −3.9 points (95% CI −5.8 to −2.0) against −2.3. (Schuster et al., 2025)
Both groups improved, which is what a placebo-controlled trial of a sleep complaint usually shows. The magnesium group improved more, by a margin that is real and modest. That is a fair description of magnesium generally: a correction rather than a transformation.
For muscle cramps — one of the most common reasons people buy it — the evidence is considerably weaker, and we would rather say so than sell the association.
The ranking compares six products on elemental dose, form and price per serving, so you can skip the arithmetic.
Educational only, not medical advice. Talk to a clinician before starting a supplement, particularly if you have kidney problems or take prescription medication.