Clinical Question

Is magnesium supplementation an effective treatment for nocturnal leg cramps?

Evidence-Based Answer

Probably not. Magnesium supplementation should not be used for short courses (less than 60 days) to treat idiopathic or pregnancy-related nocturnal leg cramps. (Strength of Recommendation [SOR]: B, systematic reviews of randomized controlled trials [RCTs], highly heterogeneous studies.) There is limited evidence that magnesium oxide may improve nocturnal leg cramps after 60 days of treatment. (SOR: B, single RCT.)

Evidence Summary

A 2020 systematic review of 11 RCTs (open-label, single-blind, or double-blind with nine parallel groups and two crossover studies; n = 735) evaluated the effectiveness of magnesium supplementation in patients of any age to prevent skeletal muscle cramps associated with pregnancy, cirrhosis, or unknown etiology.¹ The review found no reduction in leg cramps. Five trials enrolled women with pregnancy-associated leg cramps (n = 408), five trials enrolled participants with idiopathic cramps (n = 271), and one trial enrolled 29 participants with cirrhosis who reported having cramps. Most trials provided magnesium as an oral supplement in different dosing frequencies: once (three trials), twice (five trials), or three times (two trials) daily. One study provided magnesium as a five-day series of four-hour slow intravenous infusions. Nine trials compared magnesium with placebo; one trial compared magnesium with no treatment, calcium carbonate, or vitamin B; and one trial compared magnesium with vitamin E or calcium.