Does magnesium help you sleep? What the trials show

What have the trials found?

Four sets of evidence are worth knowing about.

A review of older adults. In 2021, Mah and Pitre pooled three placebo-controlled trials in 151 older adults with insomnia. People taking magnesium fell asleep 17 minutes faster on average than those on placebo. Total sleep time rose by about 16 minutes, but that difference could have been chance. The authors rated the evidence as low to very low quality, because the trials were small and at risk of bias.

An Iranian trial in older adults. The best-known of those trials, by Abbasi and colleagues in 2012, gave 46 older adults 500 mg of magnesium or placebo for eight weeks. The magnesium group slept longer, fell asleep sooner and scored better on the Insomnia Severity Index.

A 2025 trial of magnesium bisglycinate. This is the largest and most carefully run trial so far. Researchers in Germany gave 155 adults aged 18 to 65 with self-reported poor sleep either 250 mg of elemental magnesium a day as bisglycinate, or a placebo. After four weeks, insomnia scores had fallen by 3.9 points with magnesium and 2.3 points with placebo. That difference was statistically significant but small. People who ate the least magnesium in their diet seemed to benefit most.

A trial of magnesium L-threonate. In 2024, 80 adults aged 35 to 55 with sleep problems took 1 g a day of magnesium L-threonate or placebo for three weeks. The magnesium group scored better on several sleep questionnaires and on ring-tracker measures of deep and REM sleep. Several authors work for the company that distributes the branded ingredient, and the trial has not been repeated independently.

How big is the effect?

Modest. Placebo groups in sleep trials improve a lot, because believing you are being treated helps you relax. Magnesium did a little better than that. For comparison, cognitive behavioural therapy for insomnia, the treatment the NHS recommends, typically produces much larger and longer-lasting improvements.

Who is most likely to benefit?

The pattern across studies is that people who are short of magnesium gain the most. That includes older adults, who absorb less and often eat less, people with low intakes of seeds, nuts, beans and wholegrains, and people taking medicines that lower magnesium. If your diet is already rich in magnesium, expect little. Foods high in magnesium shows where you stand.

Does magnesium help with anxiety-related sleep problems?

Not proven. The sleep trials recruited people with poor sleep or insomnia, not anxiety, and the evidence for magnesium and anxiety is weak. If worry is what keeps you awake, the NHS’s advice on CBT for insomnia and talking therapies is the better-tested route.

How would you try it?

If you want to try magnesium for sleep:

• Take 200 to 400 mg of elemental magnesium in the evening, with or after food. Check the label for the elemental amount, not the compound weight.
• Choose a form that suits your gut. Glycinate and citrate are both reasonable; oxide is more likely to loosen stools.
• Give it about four weeks, then stop if you notice no difference.

Check the medicines it affects first, and don’t take supplements if you have kidney disease unless your doctor advises it.

What doesn’t the evidence show?

That magnesium fixes insomnia, that it works for everyone, or that any particular form is best. No trial has compared forms directly. Most measured sleep by questionnaire rather than in a sleep laboratory, and none lasted longer than a few months.