A patient at risk for hypercalcemia should be instructed to avoid which type of medication?

Thiazide diuretics are known to increase calcium reabsorption in the kidneys, which can lead to elevated calcium levels in the blood, contributing to hypercalcemia. This effect occurs because thiazide diuretics promote sodium reabsorption in the distal convoluted tubule of the nephron, and as sodium is reabsorbed, calcium can also be reabsorbed passively. For patients at risk for hypercalcemia, this mechanism can further exacerbate the condition.

In contrast, potassium-sparing diuretics and loop diuretics have different effects on calcium handling in the body. Loop diuretics, for instance, can actually cause hypocalcemia due to increased calcium excretion, while potassium-sparing diuretics typically do not influence calcium levels significantly. ACE inhibitors primarily affect the renin-angiotensin system and do not have a direct impact on calcium metabolism. Thus, it is crucial for individuals at risk for hypercalcemia to avoid medications like thiazide diuretics that can potentially worsen their condition.