When examining a blood panel, a veterinarian may report to the owner that a pet has hypercalcemia, which is an elevated level of calcium in the blood. The owner often then wonders if there is too much calcium in the pet's food or in the vitamins or supplements the pet is taking.
Ingesting calcium in food or canine nutritional supplements will not cause an excessive blood level. There are some diseases, though, that can cause hypercalcemia. The first thing your veterinarian will do though is to repeat the calcium test as sometimes there are false positive tests. If the second test is normal, the pet does not have a problem.
The most common cause of a high calcium level is cancer. In about half of the cases of hypercalcemia in dogs the cause is lymphoma, a cancer of the lymphatic system. Lymphoma most often causes lymph nodes to swell, but it may localize in the liver, intestine, spleen, heart, brain, spinal cord, or kidneys. Tumors of the anal glands, and less frequently, other tumors, can also cause high calcium levels. Blood tests can determine if the calcium problem is due to cancer.
Disease of one or more of the small parathyroid glands in the neck can cause hypercalcemia. A small benign tumor on a parathyroid gland can cause too much hormone to be produced, which then causes the calcium level to be too high. It is possible for a skilled professional to find these small masses on an ultrasound.
About one-third of Addison's Disease cases have high calcium levels. Addison's is a disease where too little cortisol is produced. These dogs usually act sick, with weakness, vomiting, and diarrhea often seen.
Excessive Vitamin D or similar compounds can cause a high level of calcium. These can be found in human vitamin supplements, some rat baits, and psoriasis medication made for people. Dovonex and Taclonex are brand names for prescription psoriasis creams that are especially dangerous to pets as even a small amount can cause death in pets when ingested.
Why Do We Care if the Calcium is High?
It can be very dangerous as it can cause mineralization of blood vessels, the stomach lining, and the kidneys. The kidney disease can be so severe it leads to failure.
Your veterinarian will do blood tests, and possibly chest x-rays and an abdominal ultrasound to determine the cause of the high calcium. Treatment will be directed at the underlying cause. If lymphoma is the cause, chemotherapy may be started which should lower the calcium level. If there is an anal gland tumor, surgery is indicated. Addison's Disease is treated by supplementing the hormone that is low; this may be by a daily pill or by an injection that is given every 25 days.
If the high calcium persists, or an underlying cause cannot be found, the general treatment for hypercalcemia is hospitalization with intravenous saline fluid, Lasix, and sometimes steroids.
The prognosis for hypercalcemia depends on the severity of the underlying cause. Addison's Disease can usually be well controlled. Lymphoma dogs respond to aggressive chemotherapy for an average of one to two years. If an anal gland tumor can be caught very early, surgery may be curative. Your veterinarian will investigate and determine the cause of the high calcium and discuss the prognosis and treatment plan with you.
Sources:
"Hypercalcemia Diagnosis in Dogs". Pacific Tide Newsletter, Vol 10, Issue1, Oct 2012
Pet Poison Helpline, http://www.petpoisonhelpline.com