Excess Calcium in the Blood in Cats

Hypercalcemia is a serious condition on its own, but it may also be a sign of other serious underlying conditions and should be treated as soon as possible because of the toxic effects of high levels of calcium. Symptoms may or may not appear in calcium concentrations less than or equal to 15 mg/dL. Concentrations of more than 18 mg/dL can cause life-threatening symptoms.

Calcium is an essential mineral for maintaining good health for both pets and humans. This vital mineral keeps bones and teeth strong. However, too much calcium in the blood has the potential for being life threatening in pets, including cats. The most serious effects of a cat having excess calcium in their blood is that is can cause problems with their kidneys, cardiovascular system, and nervous system. The medical term for excess calcium in the blood is hypercalcemia.

Excess calcium in the blood may lead to a variety of symptoms ranging from mild issues that may not cause initial alarm to severe life-threatening episodes.

• Increased thirst and urination
• Difficulty urinating or blood in the urine
• Lethargy
• Weakness
• Reduced appetite or refusal to eat
• Vomiting
• Constipation
• Unexplained weight loss
• Gastrointestinal function problems
• Depression
• Confusion
• High blood pressure (hypertension)
• Swollen lymph nodes
• Presence of mass on neck near voice box
• Bladder stones
• Seizures
• Muscle twitching
• Stupor and coma in extreme instances

Excess levels of calcium in a cat's blood could be caused by numerous health conditions, including:

• Poor diet or improper nutrition, including unbalanced all-meat diets
• Sudden or long-term renal failure
• Cancer or tumors, including carcinomas in the lungs, mammary glands, thyroid, pancreas, sinuses, testes or vagina
• Overactive parathyroid gland (hyperparathyroidism)
• Underactive adrenal glands (hypoadrenocorticism)
• Bone diseases, including fungal infections or cancer
• Poisoning from rat or mouse poisons
• Ingestion of calcium or vitamin supplements
• Aluminum toxicity
• Idiopathic hypercalcemia where a conclusive cause has not been determined

The diagnosis of excess calcium in a cat's bloodstream may be found during the course of a normal yearly examination performed by your veterinarian. Excess calcium can be detected through a blood chemistry profile, complete blood count, including red and white blood cells and platelets and a urinalysis. A blood test alone can lead to the diagnosis of hypercalcemia, but when used in conjunction with the other tests; it may be possible to pinpoint the cause of the disorder.

Keeping track of your cat's various symptoms can help direct your veterinarian towards finding the cause of the hypercalcemia. You may be asked various questions by your vet that can help with your pet's diagnosis. It helps to tell your veterinarian of any changes in your cat's behavior or any other symptoms that may be occurring, even if they do not seem related to excess blood calcium. Your veterinarian may also order additional diagnostic tests, including ultrasounds, X-rays or radiographs to help diagnose conditions that may be causing the excess calcium, such as cancer, bladder stones or renal disease. 

Additional tests your veterinarian may order include:

• Electrolyte panel to determine calcium, phosphorus, and salt levels
• Urine culture to rule out infections of the urinary tract
• Feline leukemia (FELV)
• Feline immunodeficiency virus (FIV)
• Parathyroid hormone (PTH) or PTH-rP concentrations

Stabilizing with Initial Treatment

Once a diagnosis of excess calcium in your cat's blood has been made, your veterinarian may request that your cat be admitted to receive intravenous fluid therapy. Upon identifying the primary cause of the hypercalcemia, the veterinarian may begin giving your cat medications to treat the now known medical condition. During your cat's hospitalization, it is likely the veterinarian will monitor its calcium levels twice a day until a normal level is reached.

Conservative Treatment Approach

Modifying your cat's diet to a low-calcium diet is normally recommended for cats with excess calcium in their blood. Alternatively, you might be advised to switch to a wet-only diet that will allow for urinary dilution and reduce the possibility of calcium oxalate that can form stones. If the cat is being fed an acidifying diet, the veterinarian will recommend switching to a high-fiber diet or other diet that will help reduce and maintain your cat's calcium blood level. If dietary changes are not enough to reduce your cat's calcium levels, the veterinarian may prescribe medications, such as glucocorticosteroids, Prednisone or other drugs to reduce calcium absorption.

Advanced Treatment Approaches

Surgery may be needed to address the conditions that have increased your cat's calcium level in their blood. This may include removing an overactive parathyroid gland. Chemotherapy may be prescribed if your cat has cancer that has caused the excess calcium in its blood.

The prognosis for cats suffering from excess calcium is generally favorable. When signs of hypercalcemia are found and treated at an early stage, the likelihood of recovery are increased. You will need to take your cat for follow-up appointments to continue monitoring any conditions that have been identified as the cause of their hypercalcemia.