Hypomagnesemia

An adult serum magnesium concentration below 0.7 mmol/L (about 0.58 mmol/L) is hypomagnesemia. The value is a starting point, not a complete severity assessment: symptoms, ECG changes, associated potassium or calcium abnormalities, ability to absorb oral therapy, and kidney function determine urgency. [1] Magnesium helps steady excitable tissues and supports ATP-dependent reactions, potassium retention, and parathyroid hormone activity. When it falls, the patient may develop tremor, cramps, tetany, seizures, hypokalemia that does not respond to potassium alone, hypocalcemia, QT prolongation, or ventricular dysrhythmias. A patient with ongoing diarrhea, alcohol use disorder, diuretic exposure, or malabsorption plus a persistently low potassium level should prompt a magnesium check. Replacement requires a second safety question: can the kidneys clear the dose? Reduced renal function increases the risk that magnesium will accumulate during treatment, so the prescribed dose, infusion rate, renal function, and post-dose magnesium level must be checked together.