What are the typical manifestations of hypomagnesemia, and how is it treated?

• A. Hypertension and tachycardia; treat with intravenous calcium.
• B. Neuromuscular irritability (tetany, seizures), arrhythmias; treat with IV magnesium sulfate and correct electrolyte abnormalities.
• C. Only oral magnesium supplements.
• D. Hyperkalemia and arrhythmias; treat with potassium.

Answer: (B)

Low magnesium leads to increased excitability of nerves and muscles and disrupts cardiac ion channel function, so the typical picture is neuromuscular irritability—things like tetany and even seizures—along with potential arrhythmias. Magnesium helps stabilize membranes and modulate calcium and potassium channels, so when it’s deficient, nerves fire more easily and the heart becomes prone to rhythm disturbances, including prolonged QT and torsades de pointes. That’s why treatment focuses on replenishing magnesium quickly with intravenous magnesium sulfate, which can rapidly relieve symptoms and reduce arrhythmic risk. At the same time, it’s important to correct accompanying electrolyte abnormalities such as potassium and calcium, since magnesium deficiency often drives these derangements and, if you only replace potassium or calcium, you may not fully correct the problem. In milder, asymptomatic cases, oral magnesium can be used for maintenance after stabilization, but acute symptomatic hypomagnesemia requires IV therapy.