Limited evidencePhysical performance

Leg Cramp Formulas

Magnesium and electrolyte blends sold for night cramps. The best available evidence says magnesium probably does not meaningfully help idiopathic cramps in older adults; results in pregnancy and with newer magnesium salts are mixed.

Evidence last reviewed: August 2026

What the science says

Idiopathic cramps in older adults Limited evidence
The 2020 Cochrane review of 11 RCTs (735 participants) concluded that magnesium is unlikely to provide a clinically meaningful reduction in cramp frequency in older adults with idiopathic cramps.
Pregnancy-related leg cramps Limited evidence
A meta-analysis of randomized trials in pregnancy reported reduced cramp frequency with oral magnesium, but the trials were small and heterogeneous, and Cochrane rated the same body of evidence conflicting.
One positive trial with a specific magnesium salt Moderate evidence
A double-blind, placebo-controlled multicentre trial of magnesium oxide monohydrate (226 mg once daily for 60 days, 175 completers) found a greater reduction in nocturnal cramp episodes than placebo. The result has not been replicated.

Dosage & safety

Studied doseTrials used roughly 200–450 mg/day of elemental magnesium at bedtime. Blends often add potassium, calcium or B vitamins, none of which has cramp-specific trial support.

SafetyMagnesium commonly causes loose stools, oxide most of all. It can accumulate dangerously in kidney impairment. Potassium-containing blends interact with ACE inhibitors, ARBs and potassium-sparing diuretics. Cramps that are new, severe or one-sided deserve a medical look.

Scientific references

Magnesium for skeletal muscle cramps
Garrison SR, Korownyk CS, Kolber MR — Cochrane Database Syst Rev, 2020
Effect of oral magnesium supplementation for relieving leg cramps during pregnancy: A meta-analysis of randomized controlled trials
Liu J, Song G, Zhao G — Taiwan J Obstet Gynecol, 2021
A randomized, double-blind, placebo-controlled, multicenter study assessing the efficacy of magnesium oxide monohydrate in the treatment of nocturnal leg cramps
Barna O, Lohoida P, Holovchenko Y — Nutr J, 2021

Where to buy

View on iHerb

Referral link — this site may earn a commission on purchases.

Related in Physical performance

Creatine (monohydrate) Strong evidence
Whey Protein Strong evidence
Caffeine Strong evidence
Beta-Alanine Moderate evidence
BCAA (Branched-Chain Amino Acids) Limited evidence
EAA (Essential Amino Acids) Moderate evidence