What is the treatment for hypomagnesemia (low magnesium levels)?

Treatment of Hypomagnesemia

For hypomagnesemia treatment, intravenous magnesium sulfate 1-2 g should be administered as a bolus for severe cases or those with cardiac manifestations, while oral magnesium oxide 12-24 mmol daily is recommended for mild to moderate cases. 1

Diagnosis and Assessment

• Hypomagnesemia is defined as serum magnesium concentration <1.3 mEq/L (normal range: 1.3-2.2 mEq/L) 1
• Common causes include decreased absorption or increased loss from kidneys or intestines (diarrhea), alterations in thyroid function, certain medications (diuretics, alcohol, pentamidine), and malnourishment 1, 2
• Most patients are asymptomatic until serum magnesium falls below 1.2 mg/dL 2

Treatment Algorithm

Severe Hypomagnesemia (Mg <1.2 mg/dL) or Symptomatic Cases:

1. Intravenous Magnesium Sulfate:

   • For cardiotoxicity and cardiac arrest: 1-2 g MgSO₄ bolus IV push (Class I, LOE C) 1
   • For severe deficiency: 250 mg/kg body weight IM within 4 hours if necessary 3
   • Alternative IV dosing: 5 g (approximately 40 mEq) added to 1 liter of 5% Dextrose or 0.9% Sodium Chloride for slow infusion over 3 hours 3

2. Monitor for signs of magnesium toxicity:

   • Have calcium chloride available to reverse potential magnesium toxicity 1
   • Deep tendon reflexes disappear as plasma magnesium approaches 10 mEq/L 3
   • Respiratory paralysis and heart block may occur at high levels 3

Mild to Moderate Hypomagnesemia:

1. Oral Magnesium Supplementation:

   • Magnesium oxide: 12-24 mmol daily (typically as 4 mmol capsules) 1
   • Best administered at night when intestinal transit is slowest for better absorption 1
   • Caution: Most magnesium salts are poorly absorbed and may worsen diarrhea/stomal output 1

2. Additional Oral Options:

   • If oral supplements don't normalize levels, consider 1-alpha hydroxy-cholecalciferol in gradually increasing doses (0.25-9.00 mg daily) 1
   • Monitor serum calcium regularly to avoid hypercalcemia 1

3. For Patients with Short Bowel Syndrome:

   • First correct water and sodium depletion to address secondary hyperaldosteronism 1
   • Reduce/avoid excess lipid in diet 1
   • Consider subcutaneous magnesium (4 mmol magnesium sulfate) with saline if needed 1-3 times weekly 1

Special Considerations

• Torsades de Pointes: IV magnesium 25-50 mg/kg (maximum: 2 g) is indicated regardless of baseline magnesium levels 1
• Refractory Status Asthmaticus: IV/IO magnesium 25-50 mg/kg (maximum: 2 g) given over 15-30 minutes 1
• Patients with Renal Impairment: Reduce dosage and monitor closely as magnesium is excreted solely by the kidneys 3, 2
• Hypokalaemia: Often coexists with hypomagnesemia and may be resistant to potassium treatment until magnesium is repleted 1, 2

Monitoring and Follow-up

• Monitor serum magnesium levels regularly during treatment 3
• For IV administration, therapeutic anticonvulsant serum levels range from 2.5 to 7.5 mEq/L 3
• Serum magnesium concentrations exceeding 12 mEq/L may be fatal 3
• In patients receiving parenteral magnesium, monitor deep tendon reflexes as an early sign of hypermagnesemia 3

Pitfalls and Caveats

• Hypomagnesemia often coexists with hypocalcemia and hypokalemia, which may not resolve until magnesium is repleted 1, 2
• Serum magnesium may not accurately reflect total body magnesium stores as most magnesium is intracellular 4
• Patients at risk of magnesium deficiency with typical symptoms should be considered for treatment even with serum magnesium within the normal range 4
• Rapid infusion of magnesium may cause hypotension and bradycardia 1
• Continuous use of magnesium sulfate in pregnancy beyond 5-7 days can cause fetal abnormalities 3