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Magnesium (sleep)

Magnesium supplements are widely used to support sleep, but randomised trials in adults give inconsistent results: small trials in older adults found people fell asleep somewhat sooner, while a 2026 systematic review of 12 trials rated the evidence low to very low certainty. Observational studies link better magnesium status with better sleep quality, which does not show cause and effect. The only claim graded moderate concerns safety: high supplemental doses commonly cause loose stools, and authorities set an adult upper level for magnesium from supplements; none of the sleep-benefit claims reach moderate because the trials are few, small, heterogeneous and at risk of bias.

  • Sleep

Evidence retrieved up to

What the research shows

Across randomised trials in adults, oral magnesium taken on its own has shown inconsistent effects on sleep: some subjective sleep measures improved modestly in some trials, while EEG, actigraphy and other measures often showed no clear difference from placebo.

Low certaintyFurther research is likely to change this.
No known concerns at usual amountsUnclear

Who this is about

adults

Practical note

Graded low: 12 trials, narrative synthesis because populations, magnesium forms, doses, durations and outcome measures varied widely; the review authors rated certainty low to very low. An earlier systematic review of observational studies and trials also found the trial results contradictory.

Sources

Among adults, magnesium from supplements at high doses commonly causes loose stools or diarrhoea, and food-safety authorities set an adult upper level of 350 mg a day for magnesium from supplements; magnesium from food is not limited in the same way.

Moderate certaintyFurther research may change the size of the effect.
Take care: see the safety noteRisk

Who this is about

adults using magnesium supplements

Practical note

Graded moderate: consistent findings summarised by regulatory risk assessment (VKM 2016, following the US Institute of Medicine 1997) and reflected in sleep trials (soft stools in one trial); downgraded from high because the underlying data are mainly older dose-response studies. Several sleep trials used doses above the 350 mg supplemental upper level.

Safety note

Osmotic diarrhoea is the most frequently reported adverse effect of magnesium salts. People with reduced kidney function have a higher risk of magnesium build-up from high-dose supplements.

Sources

In small placebo-controlled trials of older adults with poor sleep, oral magnesium was followed by falling asleep about 17 minutes sooner on average, with no statistically clear change in total sleep time; the trials were few and at moderate-to-high risk of bias.

Low certaintyFurther research is likely to change this.
No known concerns at usual amountsBenefit

Who this is about

older adults with poor sleep

Practical note

Graded low: the pooled sleep-onset result comes from 2 trials with 55 participants (downgraded for risk of bias and imprecision), and a later review of 12 trials found results inconsistent across outcomes. Trials in the meta-analysis used 320 to 729 mg of elemental magnesium a day as oxide or citrate for 20 days to 8 weeks.

Vegan note

Magnesium supplements are mineral salts and are generally vegan; capsule shells can be gelatin.

Safety note

One included trial reported soft stools in all participants taking magnesium; the other trials did not report adverse events.

Sources

In a 7-week randomised trial of 100 adults aged 51 to 85 with poor sleep quality, sleep quality scores improved by a similar amount with magnesium citrate and with placebo.

Low certaintyFurther research is likely to change this.
No known concerns at usual amountsNo clear effect

Who this is about

adults aged over 50 with poor sleep quality

Practical note

Graded low: a single randomised trial, downgraded for imprecision and because the result is one trial among a heterogeneous set. The trial used 320 mg of magnesium a day as magnesium citrate.

Sources

In observational studies of adults, better magnesium status or higher magnesium intake is associated with better sleep quality, but these studies cannot show whether low magnesium is a cause or a consequence of poor sleep.

Very low certaintyThis is uncertain; treat it as a lead, not a finding.
No known concerns at usual amountsUnclear

Who this is about

adults

Practical note

Graded very low: observational evidence (cross-sectional and cohort) from a systematic review of 9 studies, with confounding likely and the direction of the association unknown.

Vegan note

Legumes, dark green leafy vegetables, nuts, seeds and whole grains are plant sources of magnesium.

Sources