Hypomagnesemia is defined as a serum magnesium concentration of less than 0.75 mmol/L.
Etiology
The main causes include:
- Prolonged fasting, poor appetite, or long-term parenteral nutrition without magnesium supplementation.
- Significant gastrointestinal magnesium losses due to severe diarrhea, prolonged gastrointestinal suction, intestinal fistulas, or short bowel syndrome.
- Increased renal magnesium losses due to extensive use of diuretics and certain kidney disorders, which reduce magnesium reabsorption.
- Hypercalcemia, which can lower tubular reabsorption of both magnesium and phosphate.
- Conditions such as diabetic ketoacidosis, hyperthyroidism, and severe hypoparathyroidism, all of which decrease tubular reabsorption of magnesium.
Clinical Manifestations
Key symptoms include muscle tremors, carpopedal spasms, and a positive Chvostek's sign. Severe cases may present with generalized tonic-clonic seizures. Hypomagnesemia is also frequently associated with dizziness, ataxia, athetoid movements, muscle weakness, and muscle atrophy. For individuals presenting with such symptoms and underlying risk factors, the possibility of magnesium deficiency should be considered.
Hypomagnesemia can lead to cardiac arrhythmias, with electrocardiographic changes including prolonged PR intervals and QT intervals.
Treatment
Mild asymptomatic hypomagnesemia can be corrected through oral magnesium supplementation. However, oral magnesium, especially in higher doses, can often cause diarrhea. Intravenous magnesium administration is preferred for patients with absorption issues or severe hypomagnesemia. Symptomatic or severe cases are typically treated with the slow infusion of 5–10 ml of 25% magnesium sulfate in 5% glucose solution.
Considering the relatively slow distribution of magnesium from the extracellular fluid to intracellular compartments, careful magnesium supplementation may need to continue for 1–2 days, even if serum magnesium levels normalize. In addition, other electrolyte imbalances, such as hypocalcemia, hypokalemia, hypophosphatemia, and alkalosis, should also be addressed during the management of hypomagnesemia.