Sleep · Ingredient guide
Magnesium
A mineral your body uses for nerve and muscle function. It isn't a sleep signal like melatonin; the idea is that being low in it may disturb sleep. The evidence that topping it up helps is weak, and limited to older adults.
Draft: the figures on this page are being checked against the original studies before final publication.
What it is
Magnesium is a mineral involved in hundreds of chemical reactions in the body, including nerve signalling and muscle relaxation. That's why it's marketed for calm and sleep.
Supplements bind magnesium to different partner molecules, sold as oxide, citrate, glycinate, or L-threonate. Marketing makes much of these differences; the sleep evidence for any specific form is thin.
Who tends to be low
- Older adults. Deficiency is more common with age, which may disrupt sleep. All the main sleep trials were in older adults.
- Low intake. Many adults eat less than the recommended amount, especially with few nuts, seeds, beans, greens, or whole grains in their diet.
- Everyone else. If you already get enough, there's little reason to expect extra magnesium to improve your sleep.
Where it helps, and where it doesn't
The same ingredient can work well for one problem and barely at all for another, so we grade each one separately.
- C
Falling asleep, older adults with insomnia
Moderate benefit, low certainty
Three small trials (151 people) found about 17 minutes faster sleep onset than placebo. All were at risk of bias, so we can't be confident. Not listed.
- –
Sleep in younger adults
Not enough evidence
There's no good trial evidence in younger adults who aren't low in magnesium.
- –
Glycinate or threonate for sleep
Not enough evidence
One small threonate trial showed weak results; a glycinate trial is still being checked. Neither form is proven better for sleep.
How to use it, based on the evidence
- If you think you might be low, ask a doctor; they can check.
- Stay within 350 mg a day from supplements, the US upper limit for adults. Food doesn't count toward it.
- Diarrhea and cramps are the commonest side effects, especially with oxide and citrate.
- Don't take it without medical advice if you have kidney disease, and space it apart from some antibiotics and osteoporosis medicines.
Getting magnesium from food
Nuts, seeds, beans, leafy greens, and whole grains are all good sources. For most people, food covers what they need without supplements.
Listed products
- None listed yet. See what we reviewed on the not listed page.