From the Research
Allopurinol does not cause hypercalcemia. Allopurinol is a medication primarily used to treat gout and kidney stones by reducing uric acid levels in the body through inhibition of the enzyme xanthine oxidase. It has no direct effect on calcium metabolism or calcium levels in the blood. Hypercalcemia (elevated blood calcium levels) is typically caused by other factors such as hyperparathyroidism, certain cancers, excessive vitamin D intake, or medications like thiazide diuretics and lithium. If a patient taking allopurinol develops hypercalcemia, the cause is likely unrelated to the allopurinol therapy and should prompt investigation for these other common causes. Patients with concerns about calcium levels while taking allopurinol should consult their healthcare provider for appropriate evaluation, but can be reassured that allopurinol itself is not known to elevate calcium levels.
The most relevant study to this question is 1, which investigated the composition of plasma and urine in patients with recurrent calcium calculi treated with allopurinol alone, thiazide alone, and both agents together for more than 18 months. The study found that in patients treated with allopurinol, both plasma and urinary uric acid were decreased, and plasma parathyroid hormone (PTH) and urinary calcium were increased between 1 and 2 years after treatment. However, this increase in urinary calcium does not necessarily imply an increase in blood calcium levels, and the study does not provide evidence that allopurinol causes hypercalcemia.
Other studies, such as 2, 3, 4, and 5, provide information on the effects of allopurinol on uric acid levels, kidney function, and blood pressure, but do not address the question of whether allopurinol causes hypercalcemia. Therefore, based on the available evidence, allopurinol is not known to cause hypercalcemia, and patients taking this medication should be evaluated for other potential causes of elevated calcium levels if they develop hypercalcemia.