The primary cause for high calcium blood levels is hyperparathyroidism, reports the UCLA Health System. Other causes include lung or breast cancer, kidney disease, and commonly prescribed high blood pressure medications.
A single instance of high blood calcium levels can simply be due to dehydration on the day of testing or a laboratory mistake, according to the UCLA Health System. If calcium levels are recorded high on various occasions, however, it is important to determine the cause of this. The most common reason for high blood calcium levels is hyperparathyroism, when a benign tumor of the parathyroid gland causes higher than normal amounts of calcium to leave bone deposits and enter the blood. Breast, lung, oral cavity, ovary and kidney cancers can cause elevated calcium levels. In addition, lymphoma and multiple myeloma are possible causes of high blood calcium levels, but cancers are rarely the cause of hypercalcemia in healthy individuals.
High blood pressure medications, specifically those with a diuretic effect can elevate blood calcium levels because they cause the kidneys to retain calcium, reports the UCLA Health System. In a similar way, kidney failure results in hypercalcemia because calcium fails to be filtered from the blood stream. In addition to these causes, familial hypercalcemia can be inherited, and hypercalcemia can result from an excess of vitamin D.