Indications for Magnesium Supplementation
Magnesium supplementation is indicated for documented hypomagnesemia, symptomatic magnesium deficiency, and specific clinical conditions including life-threatening cardiac arrhythmias (particularly torsades de pointes), severe asthma, eclampsia/preeclampsia, and migraine. 1, 2
Clinical Indications for Magnesium Supplementation
Documented Hypomagnesemia
- Serum magnesium levels below normal range
- Symptoms of magnesium deficiency including:
- Abdominal cramps
- Impaired healing
- Fatigue
- Bone pain
- Neurological symptoms (confusion, irritability, seizures) 1
Cardiovascular Indications
- Life-threatening arrhythmias, particularly polymorphic ventricular tachycardia (torsades de pointes): IV magnesium 1-2g MgSO₄ bolus 1, 3
- Cardiac manifestations of severe hypomagnesemia 1
- Refractory hypokalemia (magnesium repletion should precede potassium replacement) 1
Other Clinical Indications
- Severe asthma exacerbations 2
- Eclampsia and preeclampsia 2
- Migraine headaches 2
- Metabolic syndrome risk reduction 2
- Dysmenorrhea symptom relief 2
- Pregnancy-related leg cramps 2
- Constipation (standard use despite limited evidence) 2
Dosing Recommendations
Oral Supplementation
- Recommended daily allowance: 320-350 mg/day for women and 420 mg/day for men 1
- Tolerable Upper Intake Level from supplements: 350 mg/day 1
- First-line oral option: Magnesium oxide at 12-24 mmol daily, preferably at night 1
- For severely malnourished patients: approximately 0.4 mmol/kg/day orally 1
Intravenous Supplementation
- For life-threatening arrhythmias: 1-2g IV MgSO₄ bolus diluted in 10 mL D5W 1
- For severely malnourished patients requiring IV supplementation: 0.2 mmol/kg/day 1
Administration Considerations
- Liquid or dissolvable magnesium products are better tolerated than pills 1
- Gradual titration is recommended to minimize gastrointestinal side effects 1
- Rehydration to correct secondary hyperaldosteronism before magnesium repletion 1
Monitoring Recommendations
- Regular monitoring of serum magnesium levels, especially in:
- Patients with renal insufficiency
- Patients on medications that affect magnesium levels (diuretics, PPIs, certain antibiotics)
- Children on calcineurin inhibitors 1
- Monitor associated electrolytes (calcium, phosphorus, potassium) 1
Contraindications and Precautions
- Severe renal impairment (creatinine clearance <20 mg/dL) 1, 4
- Existing diarrhea (may worsen with supplementation) 1
- Magnesium-restricted diet 4
- Stomach pain, nausea, or vomiting 4
- Pregnancy or breastfeeding (consult healthcare provider first) 4
- Concurrent use of certain prescription medications (potential interactions) 4
Common Causes of Magnesium Deficiency
- Medications: diuretics, proton pump inhibitors, certain antibiotics, chemotherapeutic agents 1
- Elderly patients with heart failure 1
- Polypharmacy (≥5 medications) 1
- Alcoholism 5
- Malabsorption disorders 5
- Starvation or inadequate intake 5
- Increased requirements (pregnancy, lactation, early childhood) 5
Clinical Pitfalls to Avoid
- Failing to correct hypomagnesemia before addressing hypokalemia 1
- Administering magnesium to patients with severe renal impairment without close monitoring 1, 4
- Overlooking magnesium deficiency due to normal serum levels (serum magnesium represents only 1% of total body magnesium) 6
- Administering magnesium in cardiac arrest with known or suspected hypermagnesemia (use IV calcium instead) 1
- Continuing magnesium supplementation beyond 1 week without medical supervision 4