What is the most common cause of hypermagnesemia?

Hypermagnesemia, which is an elevated level of magnesium in the blood, is most commonly caused by renal failure. In healthy individuals, magnesium is regulated by the kidneys, which excrete excess amounts to maintain homeostasis. When renal function is impaired, the kidneys cannot effectively eliminate magnesium, leading to its accumulation in the blood.

In cases of acute or chronic renal failure, the kidneys lose their ability to filter and excrete not only magnesium but also other electrolytes, resulting in hypermagnesemia. This condition can be particularly dangerous, as elevated magnesium levels can lead to severe muscle weakness, respiratory distress, and cardiac arrhythmias.

While over-supplementation and dietary excess can contribute to hypermagnesemia, these occurrences are less common in the general population compared to the impact of renal failure. Hypoparathyroidism, characterized by low levels of parathyroid hormone, does not typically lead to hypermagnesemia; instead, it is often associated with hypocalcemia. Therefore, renal failure remains the primary and most frequent cause of hypermagnesemia, making it the correct choice in this context.