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Am Fam Physician. 2023;108(6):619-620

Author disclosure: No relevant financial relationships.

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.

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Clinical Inquiries provides answers to questions submitted by practicing family physicians to the Family Physicians Inquiries Network (FPIN). Members of the network select questions based on their relevance to family medicine. Answers are drawn from an approved set of evidence-based resources and undergo peer review. The strength of recommendations and the level of evidence for individual studies are rated using criteria developed by the Evidence-Based Medicine Working Group (

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This series is coordinated by John E. Delzell Jr., MD, MSPH, associate medical editor.

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