hypomagnesemia

Hypomagnesemia is a deficiency of magnesium in the blood, usually defined as a serum level below 1.7 mg/dL (0.7 mmol/L). Magnesium is essential for many enzymatic reactions, neuromuscular function, and cardiovascular health. Total body magnesium is mostly stored in bone and muscle, so serum levels may not reflect total body stores.

Common causes include inadequate intake or absorption (malnutrition, chronic diarrhea, malabsorption, alcoholism), increased urinary losses (diuretic use, renal tubulopathies, certain medications), and shifts of magnesium into cells (refeeding after starvation, insulin therapy). Prolonged vomiting, pancreatitis, and chronic illnesses also contribute.

Symptoms range from none to neuromuscular irritability (tremor, cramps, weakness, seizures) and cardiac effects such as arrhythmias. Hypomagnesemia often worsens hypokalemia and hypocalcemia and may contribute to QT prolongation and torsades de pointes.

Diagnosis relies on measuring serum magnesium, with levels below 1.7 mg/dL supporting the diagnosis. It should be interpreted with the clinical picture and other electrolytes; ECG may show QT prolongation. Evaluation for underlying causes is recommended.

Treatment depends on severity. Mild cases may respond to oral magnesium (e.g., magnesium oxide). Moderate to severe deficiency or symptomatic patients require intravenous magnesium sulfate (for example 1–2 g IV, then a maintenance infusion) with renal function monitoring. Correct coexisting hypokalemia and hypocalcemia.

Prognosis is favorable with treatment. The condition is common in hospitalized patients and in the elderly, especially those with malnutrition or alcoholism. Recurrence warrants investigation of dietary intake, medications, and GI or renal losses.