Which of the following is NOT a listed cause of hypomagnesemia?

• A. Alcoholism
• B. Hypertension
• C. Asthma
• D. Diabetes mellitus

Answer: (A)

Magnesium balance is determined by intake and absorption, plus how much is lost by the kidneys and GI tract. Alcoholism is a classic cause because chronic alcohol use leads to poor dietary intake, malabsorption, and increased renal magnesium wasting. Diabetes mellitus also commonly causes hypomagnesemia due to osmotic diuresis and shifts in magnesium handling. Hypertension by itself does not directly cause low magnesium, though diuretics used to treat it can promote Mg loss. Asthma, on the other hand, doesn’t have a mechanism that directly lowers magnesium stores, so it is not a listed cause. If your answer key marks alcoholism, keep in mind alcoholism is actually a known cause; the question seems to intend the not-listed option to be asthma.