Benefits
High Bioavailability
Magnesium citrate is consistently rated among the most bioavailable forms — citric acid enhances solubility at gastric pH and forms a soluble complex absorbed in the small intestine. Comparable to glycinate; substantially better than oxide.
Constipation Relief
Magnesium citrate's osmotic effect draws water into the bowel, softening stool and promoting bowel movement. Doses of 200–600 mg elemental magnesium typically relieve mild constipation; high-dose (300 mL of 1.745 g/30 mL solution) is used for bowel preparation before colonoscopy.
Magnesium Deficiency Correction
Effective for replenishing magnesium status in deficient populations. Trials show meaningful increases in serum/RBC magnesium with daily supplementation.
Migraine Prevention
Magnesium (citrate or other forms) at 400-600 mg daily is supported by AHS/AAN guidelines (Level B) for episodic migraine prevention.
Kidney Stone Prevention
Magnesium citrate may modestly reduce calcium oxalate kidney stone formation — citrate inhibits calcium oxalate crystallization independently. Better-evidenced for potassium citrate but magnesium citrate is sometimes used.
Mechanism of action
Citric Acid Solubilization
Citric acid's three carboxyl groups complex with magnesium, maintaining solubility across gastric pH changes and improving absorption via standard divalent cation pathways.
Osmotic Bowel Effect
Unabsorbed magnesium and citrate ions in the bowel pull water into the lumen via osmosis, increasing stool volume and softening — laxative effect at higher doses.
NMDA Receptor and Calcium Channel Modulation
Magnesium gates NMDA receptors and modulates voltage-gated calcium channels in vascular smooth muscle and neurons — basis for migraine prevention and vasodilatory effects.
ATP Cofactor
Mg-ATP is the biologically active form of ATP; magnesium is required cofactor for >300 enzymes including all ATPases.
Clinical trials
Crossover trial comparing magnesium citrate, glycinate, and oxide bioavailability in healthy adults. Outcomes: serum magnesium, urinary excretion, RBC magnesium. (Walker et al. 2003, Magnes Res)
Healthy adults.
Magnesium citrate produced significantly higher absorption vs oxide; comparable to glycinate. Higher 24-hour urinary excretion confirmed superior absorption. Established citrate as among the most bioavailable forms.
RCT of magnesium citrate (600 mg/day) vs placebo in 40 migraine patients for 12 weeks. (Köseoglu et al. 2008, Magnes Res)
40 migraine patients.
Magnesium citrate significantly reduced migraine frequency, severity, and duration vs placebo. Supports magnesium's place in AHS/AAN guidelines (Level B). Diarrhea was common side effect.
About this ingredient
Magnesium citrate is magnesium bound to citric acid — among the most clinically-used magnesium forms. Elemental magnesium content: ~16% by weight (1,000 mg magnesium citrate = ~160 mg elemental Mg). DUAL-PURPOSE — both supplemental magnesium AND osmotic laxative depending on dose.
CRITICAL DOSE-EFFECT RELATIONSHIP: low doses (100-200 mg elemental Mg) provide repletion with minimal GI effects; mid doses (300-400 mg) cause some loose stools in many people; high doses (>500 mg or full bowel-prep doses) reliably cause diarrhea. MEDICAL USE: 'Magnesium Citrate Solution' (10 fl oz of 1.745 g/30 mL = 290 mg/15 mL elemental Mg per dose; OTC) is widely used for bowel preparation before colonoscopy and for occasional constipation.
EVIDENCE-BASED USES: (1) Magnesium repletion (high bioavailability); (2) Constipation (FDA-approved laxative use); (3) Bowel prep; (4) Migraine prevention (Köseoglu 2008); (5) Kidney stone prevention (modest); (6) Standard general magnesium supplementation.
CRITICAL CAUTIONS: (1) DIARRHEA at high doses — predictable; (2) DEHYDRATION with bowel-prep doses; (3) RENAL IMPAIRMENT — hypermagnesemia risk; CKD consult; (4) HEART BLOCK — IV high-dose contraindicated; (5) DRUG INTERACTIONS — separate from bisphosphonates, tetracyclines, quinolones, levothyroxine by 2-4 hours; (6) DEHYDRATION/KIDNEY FUNCTION — monitor with chronic high-dose use; (7) Pregnancy/lactation safe at typical doses; (8) When citrate's laxative effect is undesirable, MAGNESIUM GLYCINATE is the preferred alternative.