Hypercalcemia in Cats
The term “calcemia” refers to the level of calcium in the blood. Calcium is a natural element found in the body and on the earth and is abbreviated on the periodic table as “Ca.” Hypercalcemia means high calcium, while hypocalcemia means low calcium. Both conditions can potentially be life threatening and should be treated as soon as possible.
The diagnosis of hypercalcemia is based on two blood tests: a total serum calcium level, and an ionized calcium level (often abbreviated iCa). A total serum calcium level is very easy to measure, and most veterinarians can routinely test for this. Normal total serum calcium is approximately 8-11 mg/dL, with significant hypercalcemia being defined as more than 10.5 mg/dL in cats. An ionized calcium level is slightly more difficult to measure, and is only readily available as a send out test or at most specialty clinics or emergency clinics. Ideally, an ionized calcium level should be performed as it is more specific and more accurate. Normal ionized calcium levels are either 1.12-1.32 mmol/L or 4.5-5.3 mg/dL, with significant hypercalcemia being defined as more than 1.4 mmol/L or >5.5 mg/dL.
What causes hypercalcemia in cats?
In cats, hypercalcemia can be caused by:
- Idiopathic hypercalcemia in cats (no known medical cause)
- Inappropriate diet or nutrition
- Kidney failure – both acute and chronic
- Primary hyperparathyroidism (i.e., an overactive parathyroid gland)
- Diseases affecting the bone (e.g., cancer or fungal infections in the bone)
- Hypoadrenocorticism (due to underactive adrenal glands)
- Poisonings (e.g., cholecalciferol mouse and rat poison, Dovonex psoriasis cream, calcium supplements, vitamin D, etc.)
- Aluminum toxicity (e.g., from oral phosphate binders to lower the phosphorous levels in the body)
Symptoms of hypercalcemia in cats:
- Not eating or decreased appetite
- Lethargy and weakness
- Excessive thirst and urination (although this is subtle in cats)
- Weight loss
- Enlarged lymph nodes (if associated with lymphosarcoma [cancer])
- A mass near the voice box on the neck (which may be a parathyroid gland tumor)
- Straining to urinate, difficulty urinating, or even bloody urine secondary to calcium-containing crystals or stones in the bladder
The work up for hypercalcemia in cats can be initially expensive because it’s important to rule out serious causes of hypercalcemia such as hypercalcemia of malignancy – a high calcium level secondary to cancer. While this is more common in dogs, it can rarely be seen in cats. Once all these tests
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Justine has more than 18 years of experience in the veterinary industry and is a board-certified emergency critical care veterinary specialist and toxicologist as well as the CEO and founder of Vetgirl. She is also a founding member of IDEXX’s Pet Health Network team.