Magnesium for Muscle Cramp
Across the best available trials, oral magnesium does not meaningfully reduce muscle cramps for most people, including older adults and pregnant women, and it should not be relied on for cramp prevention or treatment.
Why this grade7-layer evidence engine
This claim earns a D (Counter-Evidence, disputed) because the highest-quality data point against a benefit. A 2020 Cochrane review (PMID 32956536; n=735, 11 trials) found that for idiopathic cramps in older adults the change in cramp frequency was small and not statistically significant (MD -9.59%, 95% CI -23.14% to 3.97%, crossing zero). A 2021 meta-analysis in pregnant women (PMID 34247796; n=332, 4 trials) likewise found no significant effect on cramp frequency (P=0.167) or recovery (P=0.207), overturning the older idea that pregnancy is a responsive subgroup.
More recent direct evidence reinforces this. In a 2026 three-arm Finnish RCT (PMID 41680812; n=121), magnesium was no better than placebo (P=0.929), while compression stockings did help (adjusted MD -1.43, P=0.001) — pointing patients toward a non-drug option that actually worked. The lone positive signal, a 2021 Ukrainian trial of magnesium oxide monohydrate (PMID 34719399; n=175), showed only about 0.8 fewer cramps per week versus placebo and sat against a very large placebo response (~2.6 fewer cramps/week), so it is likely formulation- or population-specific rather than a real, generalizable effect.
Institutional opinion is genuinely split, which is why the engine marks it disputed rather than clearly negative. Harvard Health states that 'most nonpregnant people given oral magnesium supplements do not benefit,' and the NHS notes you 'should be able to get all the magnesium you need by eating,' while Mayo Clinic still suggests magnesium glycinate 'may help' — a stance now out of step with the trial data. Notably, no major regulator (FDA, EFSA, WHO, NHS) lists muscle cramps as an approved use; magnesium's recognized roles are normal muscle function and conditions like pre-eclampsia, not cramp relief.
Scoring transparency
All scores computed by a 7-layer evidence engine — fully auditable▸View the full decision path (audit trail)
- compute_raw_score — 加權公式: L2×0.30 + L3×0.25 + L5×0.25 + L11×0.10 + L1×0.10 = 0.34
- tier_from_score — 依分數區間映射至 tier letter
- apply_hec_rules — 高階證據未達主導 (0 positive vs 1 negative)，由 raw_score 決定
- tier_strict_requirement_check — Tier 條件達標，未降階
- detect_disputes — 偵測到 1 個 hard + 0 個 soft dispute
- decide_status — 依 tier + dispute 結果決定 status