Do you give magnesium (Mg) with calcium in cases of hypocalcemia?

Magnesium Supplementation in Hypocalcemia

Yes, magnesium supplementation should be given with calcium in cases of hypocalcemia, especially when hypomagnesemia is present, as magnesium is necessary for proper calcium metabolism and cellular function. 1

Rationale for Combined Supplementation

Magnesium plays several critical roles in calcium homeostasis:

• Magnesium is necessary for the movement of sodium, potassium, and calcium into and out of cells and plays an important role in stabilizing excitable membranes 1
• Hypomagnesemia can worsen or contribute to hypocalcemia, particularly in patients with hypoparathyroidism 1
• Low magnesium levels can impair parathyroid hormone function, further compromising calcium regulation

Clinical Guidelines for Management

When to Check Magnesium Levels

• Always measure magnesium levels when evaluating hypocalcemia
• Regular investigations should include calcium, parathyroid hormone, magnesium, and creatinine concentrations 1

Magnesium Supplementation Protocol

• For patients with documented hypomagnesemia (<1.3 mEq/L) and hypocalcemia:
  • Provide magnesium supplementation alongside calcium and vitamin D
  • For severe cases with cardiac manifestations: IV magnesium 1-2 g MgSO₄ bolus 1

Special Considerations

22q11.2 Deletion Syndrome

In patients with 22q11.2 deletion syndrome:

• Magnesium supplementation is specifically indicated for those with hypomagnesemia 1
• Hypocalcemia in these patients is typically attributable to hypoparathyroidism, and hypomagnesemia may be an associated finding 1

Cardiac Manifestations

• Hypomagnesemia can be associated with polymorphic ventricular tachycardia, including torsades de pointes 1
• For cardiotoxicity and cardiac arrest related to hypomagnesemia, IV magnesium 1-2 g of MgSO₄ bolus is recommended (Class I, LOE C) 1

Potential Pitfalls and Monitoring

Risks of Hypermagnesemia

• Excessive magnesium supplementation can lead to hypermagnesemia, causing:
  • Neurological symptoms: muscular weakness, paralysis, ataxia, drowsiness, confusion 1
  • Cardiovascular effects: vasodilation, hypotension, bradycardia, cardiac arrhythmias 1, 2
  • In severe cases: respiratory depression and cardiorespiratory arrest 1, 2

Monitoring Requirements

• Monitor serum magnesium, calcium, and renal function during supplementation
• For patients receiving IV magnesium, continuous cardiac monitoring is advised
• If hypermagnesemia develops, calcium can be administered as a physiological antagonist (calcium chloride [10%] 5-10 mL or calcium gluconate [10%] 15-30 mL IV over 2-5 minutes) 1, 3

Evidence Considerations

While some older research suggested that magnesium infusion might cause hypocalcemia by suppressing parathyroid hormone secretion 4, 5, more recent evidence indicates that magnesium supplementation does not negatively affect calcium levels in treated hypoparathyroid patients 6. The benefits of correcting hypomagnesemia when present alongside hypocalcemia outweigh potential risks, especially when appropriate monitoring is in place.