Hypercalcemia (High Blood Calcium) in Cats

Overview of Feline Hypercalcemia

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 on hypercalcemia in cats 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.

What to Watch For

Diagnosis of Hypercalcemia 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. Diagnostic tests are needed to recognize hypercalcemia and exclude other diseases causing similar symptoms. Tests may include:

Treatment 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 concentration is 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 very high blood calcium concentration is allowed to persist.

Home Care and Prevention

Administer any medications prescribed by your veterinarian. Follow-up with your veterinarian for physical examinations and repeated testing of blood calcium concentration.

If the underlying cause of hypercalcemia is not identified on initial evaluation, or if your cat responds inadequately to treatment, further diagnostic evaluation and treatment will be necessary.

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 malacoxylon and Trisetum flavescens.

In-depth Information on Hypercalcemia in Cats

Several serious medical conditions can result in hypercalcemia. It is important to identify the underlying cause of hypercalcemia in your cat so that effective treatment can be instituted. Disorders that can cause hypercalcemia include:

Diagnosis In-depth

Veterinary care should include diagnostic tests and subsequent treatment recommendations. Diagnostic tests must be performed to confirm the cause of hypercalcemia and exclude other diseases. The following diagnostic tests may be recommended:

Your veterinarian may recommend additional diagnostic tests to exclude or diagnose other conditions or to better understand the impact of hypercalcemia. These tests insure optimal medical care and are selected on a case-by-case basis. Examples include:

The decision to perform some diagnostic tests will be made based on the likelihood of specific disease processes. Your veterinarian will make these decisions on the basis of your cat’s medical history and physical examination results. Some underlying disorders that may cause hypercalcemia and prompt your veterinarian to run specific tests include:

Treatment In-depth

Initial therapy should be aimed at the diagnosis and treatment of the underlying cause of the hypercalcemia. Treatment of hypercalcemia must be individualized based on the severity of the condition and its underlying cause.

Moderate to severe hypercalcemia is a medical emergency because hypercalcemia has adverse effects on several organ systems, notably the kidneys, heart, nervous system, and intestinal tract. The decision to begin aggressive medical therapy is based on clinical symptoms, abnormalities of kidney function, abnormalities on the electrocardiogram (ECG), and nervous system abnormalities.

Symptomatic cats – those with increased water consumption and urination, loss of appetite, and lethargy – that have calcium concentrations greater than 15 milligrams per deciliter (mg/dl) of blood require immediate treatment. Such cats are at risk for mineralization of their soft tissues, including their kidneys.

Emergency Treatment of Hypercalcemia in Cats

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