What is the treatment for hypomagnesemia?

Treatment of Hypomagnesemia

Magnesium replacement is the cornerstone of hypomagnesemia treatment, with intravenous magnesium sulfate recommended for symptomatic or severe cases (serum Mg <0.5 mmol/L), while oral supplementation is appropriate for mild, asymptomatic deficiency. 1

Route Selection Based on Severity

Intravenous Magnesium Sulfate (First-Line for Severe Cases)

For severe hypomagnesemia (serum Mg <0.5 mmol/L) or symptomatic patients, IV magnesium sulfate is indicated. 2, 3

• Mild deficiency: 1 g (8.12 mEq) IM every 6 hours for 4 doses (total 32.5 mEq/24 hours) 2
• Severe hypomagnesemia: Up to 250 mg/kg (approximately 2 mEq/kg) IM over 4 hours, or 5 g (40 mEq) added to 1 liter of IV fluid infused over 3 hours 2
• Rate of administration: Generally should not exceed 150 mg/minute (1.5 mL of 10% solution) except in life-threatening situations 2
• Life-threatening arrhythmias (torsades de pointes): 1-2 g IV bolus push is recommended 1

Oral Magnesium (For Mild Cases)

For patients with serum magnesium 0.5-0.7 mmol/L who are asymptomatic, oral supplementation is appropriate. 1, 3

• Magnesium oxide: 12-24 mmol daily (4 mmol capsules, typically given at night when intestinal transit is slowest) 1
• Oral magnesium salts are poorly absorbed and may worsen diarrhea, making magnesium oxide the preferred formulation as it contains more elemental magnesium 1

Critical First Step: Address Underlying Causes

Rehydration to correct secondary hyperaldosteronism is the most important initial intervention before magnesium replacement. 1

• Water and sodium depletion must be corrected first, as hyperaldosteronism increases renal magnesium wasting 1
• Identify and discontinue offending medications (cisplatin, cetuximab, aminoglycosides, diuretics, proton pump inhibitors) 1, 4

Special Populations and Contexts

Cancer Patients on Chemotherapy

• Chemotherapy agents (cisplatin, cetuximab) commonly cause significant hypomagnesemia 1
• IV magnesium sulfate may reverse neurological symptoms including confusion, hallucinations, irritability, nystagmus, seizures, and severe pain 1
• Regular monitoring of magnesium levels is essential in this population 1

Patients on Kidney Replacement Therapy (KRT)

Dialysis solutions containing magnesium should be used to prevent hypomagnesemia during KRT rather than IV supplementation. 1

• Hypomagnesemia occurs in up to 60-65% of critically ill patients on continuous KRT, especially with citrate anticoagulation 1
• Commercial KRT solutions enriched with magnesium are widely available and safer than exogenous IV supplementation 1
• IV supplementation in patients on CKRT is not recommended 1

Short Bowel Syndrome

• If oral magnesium fails to normalize levels, add oral 1-alpha hydroxycholecalciferol 0.25-9.00 mg daily (titrate every 2-4 weeks) 1
• Monitor serum calcium regularly to avoid hypercalcemia 1
• Reduce excess dietary lipid, which can worsen magnesium absorption 1
• Occasionally, subcutaneous or intramuscular magnesium sulfate infusions with saline may be necessary 1

Monitoring and Safety Considerations

Caution must be observed to prevent exceeding renal excretory capacity during replacement. 2

• In severe renal insufficiency, maximum dosage is 20 g/48 hours with frequent serum magnesium monitoring 2
• Target therapeutic serum magnesium level: 1.5-2.5 mEq/L (normal range) 2
• For seizure control in eclampsia, target level is 6 mg/100 mL 2
• Continuous maternal administration beyond 5-7 days in pregnancy can cause fetal abnormalities 2

Common Pitfalls to Avoid

• Do not attempt rapid oral correction in symptomatic patients—IV route is essential for severe or symptomatic hypomagnesemia 3, 4
• Do not use oral magnesium-containing antacids in hypophosphatemia—this is contraindicated 3
• Reduce magnesium dose in renal insufficiency and constipation to prevent toxicity 3
• Do not overlook concurrent electrolyte abnormalities—hypomagnesemia often coexists with hypocalcemia and hypokalemia, which may not correct until magnesium is repleted 1