What Causes High Calcium in Cats?

Excess amounts of calcium in your beloved cat’s system can sometimes be caused by vitamin D toxicosis. Over a 24 to 72 hour period, your cat may experience a wide range of distressing symptoms associated with his hypercalcemia, including vomiting, diarrhea, weakness, depression, anorexia, polyuria (increased urination) and polydipsia (increased thirst). Vitamin D poisoning is most commonly caused by the ingestion of certain plants, rodenticides, supplements or food.

The parathyroids are four small kidney-shaped glands adjacent to the thyroid glands on Kitty's neck. These glands secrete the PTH hormone which works hand-in-hand to regulate blood calcium. When parathyroid glands function abnormally, calcium in the body can rise to dangerous levels. To determine a parathyroid malfunction, your veterinarian will take a measurement of the ionized calcium concentration of your cat’s blood.

Cancers and tumors are a possible cause of high calcium in cats. The most common tumor types that accompany hypercalcemia include lymphoma and squamous cell carcinoma. Lymphoma originates in the lymphocyte cells, a type of white blood cell that is crucial to your pet’s defenses in the immune system. While squamous cell carcinoma tumors are generally fast-growing, an early diagnosis may improve your cat’s prognosis.

In cats, one of the most common causes of hypercalcemia is chronic renal failure. More common in older cats, this form of kidney disease is normally caused by kidney tumors, infections, damage to the kidneys or polycystic kidney disease. Bone deteriorating diseases may also be to blame for your cat’s diagnosis of hypercalcemia. In rare cases, high calcium levels may be due to aluminum toxicity or under-functioning adrenal glands.