Magnesium

What the evidence says

Magnesium is required for neuromuscular, metabolic, and bone functions. Supplementation is clearly appropriate when deficiency or excessive loss is identified, but serum magnesium can miss some depletion and symptoms such as fatigue or cramps are nonspecific.^[1]

For blood pressure, a 2025 meta-analysis of 38 randomized trials found average reductions of about 2.8 mmHg systolic and 2.0 mmHg diastolic, with larger effects in people with hypomagnesemia or treated hypertension. That is a modest adjunctive effect, not a substitute for antihypertensive care.^[3]

Migraine evidence is promising but heterogeneous: a 2024 supplement meta-analysis reported fewer attacks and migraine days, while NIH notes that preventive doses often exceed the supplement upper limit and should be clinician-supervised. By contrast, a Cochrane review found magnesium unlikely to help ordinary skeletal-muscle cramps in older adults.^[4][1][5]

Unabsorbed magnesium commonly causes diarrhea, nausea, and cramping. Severe toxicity is uncommon with normal kidney function but can cause hypotension, weakness, breathing difficulty, arrhythmia, or cardiac arrest when renal clearance is impaired or doses are extreme. Magnesium also reduces absorption of some antibiotics and bisphosphonates unless separated in time.^[1][2]