High Calcium in Cats: Causes, Symptoms & What to Do About It

Hypercalcemia refers to an abnormally high blood concentration of calcium. Blood calcium concentrations are measured in milligrams (mg) per deciliter (dl). One hundred milliliters equals one deciliter.

Normal values for blood calcium concentration vary slightly from one laboratory to another, but approximately 9.0 to 11.6 mg/dl is considered normal in adult cats. Blood calcium concentrations above 13.0 mg/dl are abnormal and warrant diagnostic evaluation and treatment.

Below is an overview of high level of calcium in the blood, followed by detailed information on the diagnosis and treatment of this condition.

Some relatively common (and benign) situations can cause erroneously high blood calcium concentrations to be reported by the laboratory depending on the analyzer used. Examples include blood samples with high fat content (lipemia) due, for example, to collection of blood soon after a meal or release of hemoglobin from the red blood cells during processing of the blood (hemolysis).

Certain anticoagulants and detergents used to clean laboratory glassware also may cause erroneously high blood calcium concentrations to be reported. In these situations, the blood calcium concentration should be determined again using a properly collected blood sample that is free of lipemia and hemolysis.

Dehydration is a common clinical situation that can result in mildly increased blood calcium concentration. Blood calcium concentration should be re-evaluated after the patient has been rehydrated by intravenous or subcutaneous (under the skin) administration of fluids.

Symptoms of High Calcium in Cats

• Loss of appetite
• Increased urine production
• Increased water consumption
• Vomiting
• Weakness
• Lethargy
• Dehydration

Diagnosis of High Calcium Level in Cats

A thorough diagnostic evaluation of the cat is necessary if hypercalcemia persists after correction of lipemia, hemolysis, and dehydration, because high blood calcium concentration can be a marker of some serious underlying disease processes including several different types of cancer.

Routine laboratory testing provides information about the total concentration of calcium in the blood. It also may be necessary, however, for your veterinarian to have the laboratory measure the active component of blood calcium (ionized calcium). This component contributes to many of the clinical symptoms and physiologic consequences of hypercalcemia.

The symptoms of hypercalcemia are nonspecific. A diagnosis of exclusion may be required to eliminate other diseases causing similar symptoms. Tests may include:

• A complete medical history. The medical history will include questions about changes in water consumption and urination, change in appetite, weight loss, previous illnesses, medications being given, and exposure to toxins such as vitamin D-containing rat poison, vitamin D-containing topical ointments, or toxic plants.
• Physical examination may include palpation of the abdomen to evaluate for enlargement of the liver or spleen, palpation of lymph nodes located under the skin to detect enlargement, palpation of the anal sacs to detect masses, and listening to the chest with a stethoscope.
• A complete blood count (CBC) to evaluate red blood cell count and rule out anemia and blood protein concentration.
• Serum biochemistry tests to evaluate your cat’s general health and determine the effects of hypercalcemia on other body systems, especially the kidneys.
• Urinalysis to evaluate the effects of hypercalcemia on the ability of the kidneys to concentrate urine.
• Blood ionized calcium concentration to evaluate the biologically active form of calcium.

Management of Hypercalcemia in Cats

Treatment for hypercalcemia is determined by the underlying cause and the severity of your cat’s hypercalcemia and its effects on kidney function. Emergency treatment may be necessary when blood calcium concentrations are very high. This may include hospitalization for intravenous fluid therapy and drug treatment.

Serious damage to the kidneys and mineralization of soft tissues can occur if a very high blood calcium concentration is allowed to persist.

Emergency Treatment of Hypercalcemia in Cats

• Intravenous administration of fluids, usually a physiologic salt solution, facilitates the excretion of calcium in the urine.
• Administration of the diuretic drug (furosemide (Lasix®)) also facilitates excretion of sodium and calcium in the urine.
• Cortisone-like drugs (prednisone) can limit bone release of calcium, decrease intestinal absorption of calcium, and increase excretion of calcium in the urine. These drugs can have a direct toxic effect on some cancer cells, specifically, malignant lymphocytes, and, if possible, they should not be given until a definitive diagnosis has been made.
• A new class of drugs called diphosphonates can be given to decrease bone release of calcium.
• Many other drugs (some with potentially serious adverse effects) may be required to treat cats with refractory hypercalcemia. Examples include mithramycin, calcitonin, and ethylenediaminetetraacetic acid (EDTA).
• Above all, it is crucial to treat the underlying disease process that is causing hypercalcemia.

Optimal treatment for your cat requires a definitive diagnosis and a combination of home and professional veterinary care. Follow-up is crucial and includes:

• Administering any veterinary prescribed medications.
• Allowing your cat unlimited access to fresh clean water.
• Follow-up with your veterinarian for examinations and repeated measurements of blood calcium concentration.
• Other recommendations will be determined by the underlying cause of hypercalcemia.
• Contact your veterinarian immediately if you have trouble treating your cat.

Home Care and Prevention

Make sure your cat has free access to ample amounts of fresh drinking water. Avoid exposure of your cat to toxins known to cause hypercalcemia such as vitamin D-containing rat poisons, topical ointments containing vitamin D-like compounds like calcipotriene, and plants such as day-blooming Jessamine (Cestrum diurnum), Solanum melanoxylon, and Trisetum flavescens.