Magnesium Supplementation for Sleep in Adults: A Systematic Review of Randomized Controlled Trials

Magnesium supplementation is commonly used to support sleep, but evidence remains mixed. This review evaluated randomized controlled trials of oral magnesium administered as a stand-alone intervention for sleep-related outcomes in adults. PubMed/MEDLINE, Scopus, Cochrane CENTRAL, ClinicalTrials.gov, and the WHO International Clinical Trials Registry Platform were searched from inception to 1 June 2026. Eligible studies were randomized controlled trials evaluating magnesium as the only active intervention, or including a magnesium-only arm, and reporting at least one sleep-related outcome in adults. Trials involving nocturnal leg cramps, restless legs syndrome, or periodic limb movements were synthesized separately. Risk of bias was assessed using the Cochrane Risk of Bias 2 tool, certainty of evidence using the Grading of Recommendations Assessment, Development and Evaluation approach, and findings were synthesized narratively because of study heterogeneity. Twelve randomized controlled trials were included in the main synthesis on sleep, insomnia, or poor sleep, and three additional trials involving movement- or cramp-related sleep disturbance were analyzed separately. One separately analyzed restless legs syndrome trial enrolled participants aged 15-50 years because adult-only data were unavailable. Populations, magnesium formulations, elemental doses, treatment durations, outcome roles, and measures varied substantially. Findings were inconsistent across subjective outcomes, EEG, research-grade actigraphy, consumer wearable-derived estimates, and physiological markers. Certainty of evidence was low to very low. Current evidence does not support oral magnesium as a routine treatment for insomnia. It may provide modest benefits for selected subjective outcomes in some adults, but the findings are inconsistent, and the certainty of the evidence is low or very low. Further well-designed, adequately powered trials are required before routine recommendations can be made.