Magnesium

• Migraine prevention: Research suggests oral magnesium can modestly reduce migraine attack frequency and severity, particularly in those with low magnesium status (moderate evidence from guidelines and systematic reviews).
• Blood pressure: Meta-analyses of RCTs show small but statistically significant reductions in systolic/diastolic blood pressure (roughly a few mmHg), with greater effects in deficiency or hypertension (moderate evidence).
• Glycemic control/insulin sensitivity: Systematic reviews indicate small improvements in fasting glucose and insulin sensitivity in people with insulin resistance or type 2 diabetes, especially if magnesium-deficient (moderate evidence).
• Constipation (osmotic laxative effect of certain salts): Magnesium hydroxide and citrate reliably increase stool water and bowel movements for short-term relief (strong evidence for laxative effect of these salts; not intended for chronic use without supervision).
• Premenstrual syndrome (PMS)/dysmenorrhea: Some RCTs report reductions in swelling, mood symptoms, and cramps; effects are modest and inconsistent across studies (emerging to moderate evidence).
• Sleep quality and perceived stress: Small trials suggest possible improvements in sleep efficiency and subjective anxiety/stress, mainly in older adults or those with low magnesium; results are mixed (emerging evidence).
• Bone health: Higher dietary magnesium intake is associated with better bone mineral density; interventional data with supplements are limited and mixed (emerging evidence).

Common (dose/form dependent): diarrhea, loose stools, abdominal cramping, nausea; GI effects are more frequent with magnesium oxide and citrate and at higher doses. Mild drowsiness/relaxation may occur. Less common: bloating, hypotension, dizziness, fatigue—more likely at higher intakes or with antihypertensives. Rare but serious (usually with renal impairment or excessive intake, including overuse of magnesium-containing laxatives/antacids): hypermagnesemia with flushing, lethargy, vomiting, muscle weakness, diminished reflexes, hypotension, bradycardia, heart block, respiratory depression, and in extreme cases cardiac arrest. Other considerations: can reduce absorption of several medications (e.g., certain antibiotics, thyroid hormone, bisphosphonates), potentially leading to therapeutic failure if doses are not separated.

Typical supplemental ranges reported in studies: about 100–400 mg/day of elemental magnesium, with higher ends more likely to cause GI effects. In clinical trials for specific outcomes: migraine prevention often 400–600 mg/day elemental; blood pressure and glycemic endpoints commonly 240–600 mg/day; constipation relief uses magnesium hydroxide or citrate in laxative doses for short-term use. Optimal dose varies by individual status and goal. Forms/bioavailability: organic salts (e.g., citrate, glycinate, malate) tend to be better absorbed and sometimes better tolerated than oxide, though individual response varies. Oxide has lower bioavailability and more laxative effect. Timing with medications: to reduce chelation/absorption issues, many sources recommend separating magnesium from interacting drugs (e.g., certain antibiotics, levothyroxine, bisphosphonates, HIV integrase inhibitors) by at least 2–4 hours. Intake context: the adult RDA is ~310–420 mg/day from all sources (age/sex dependent). The tolerable upper intake level (UL) for magnesium from supplements and medications (excluding food) is 350 mg/day for adults, set to minimize diarrhea; higher therapeutic doses have been used in trials under supervision.

• Significant kidney disease (e.g., eGFR <30 mL/min/1.73 m²) or acute kidney injury: risk of hypermagnesemia.
• Myasthenia gravis or known heart block/bradyarrhythmias: magnesium can depress neuromuscular transmission and AV conduction.
• Bowel obstruction or ileus; chronic, unexplained abdominal pain: avoid magnesium laxatives.
• Chronic diarrhea or severe dehydration: may worsen fluid/electrolyte imbalance.
• Low baseline blood pressure or symptomatic orthostatic hypotension: additive BP-lowering possible.
• Pregnancy/breastfeeding: dietary amounts are appropriate; higher-dose supplements or laxative salts should be used only under medical supervision. (Note: IV magnesium sulfate for preeclampsia is prescription-only and outside dietary supplementation.)
• Perioperative: high-dose magnesium can potentiate neuromuscular blockers and sedatives; many clinicians advise stopping nonessential high-dose magnesium/laxative forms ~1 week before elective surgery—discuss timing with surgeon/anesthesiologist.
• Not known to directly increase bleeding risk; no specific anticoagulant interaction, but still disclose use before procedures.