Symptoms of hypomagnesemia occur when there is depletion of body stores, which usually correlates with serum levels < 0.5 mmol/L (< 1 mEq/L).
A patient with a minor, transient drop in serum magnesium will usually be asymptomatic if the body stores are normal.
A patient may have normal serum magnesium levels yet show symptoms responsive to magnesium repletion.
Clinical findings in clinical hypomagnesemia:
(1) hypocalcemia (magnesium depletion causes impaired secretion of parathyroid hormone and target organ resistance)
(2) hypokalemia
(3) muscle weakness
(4) muscle irritability or tetany
(5) cardiac arrhythmias associated with irritability (atrial tachycardia, atrial fibrillation, ventricular premature complexes, ventricular tachycardia, ventricular fibrillation)
(6) delirium
(7) seizures
where:
• Some of the neuromuscular findings may reflect the hypocalemia and hypokalemia.
Hypomagnesemia can be hard to diagnose and requires a high index of suspicion, especially in a patient with:
(1) unexplained findings who has one or more risk factors for low intake or high wastage or
(2) hypcalcemia or hypokalemia who does not respond as expected to standard replacement therapy
