Hypercalcemia

What Is Hypercalcemia?

Hypercalcemia is a higher-than-normal level of calcium in the blood. Calcium is essential for muscles, nerves, and bones, and the body normally keeps it in a tight range using parathyroid hormone and vitamin D. When that balance breaks down, high calcium can damage the kidneys, form bladder stones, and make a pet feel unwell. Hypercalcemia is not a disease on its own but a sign that something else needs to be found.

Common Causes

In dogs:

• Cancer, most often lymphoma and anal sac adenocarcinoma (a tumor of the anal glands), which release a hormone-like protein that raises calcium
• Primary hyperparathyroidism, usually from a small benign parathyroid tumor; Keeshonds have an inherited form
• Kidney disease
• Addison’s disease (low adrenal hormones)
• Vitamin D poisoning from cholecalciferol rodent baits, some psoriasis creams, or over-supplementing; ask before giving vitamins
• Some fungal infections and inflammatory diseases

In cats: idiopathic hypercalcemia (no cause found) is the most common type, followed by kidney disease, cancer, and vitamin D toxicity. It is linked to calcium oxalate bladder and kidney stones.

Signs Owners Notice

• Drinking a lot of water and urinating more
• Reduced appetite, vomiting, or constipation
• Weakness, tiredness, or muscle twitching
• Straining to urinate or blood in the urine if stones form
• Many pets, especially cats, show few or no signs at first

Diagnosis and Treatment

A routine blood panel may show high total calcium; an ionized calcium test confirms whether the active form is truly raised. To find the cause, vets often check parathyroid hormone, a cancer-associated protein (PTHrP), and vitamin D levels, along with a urine test, chest and belly imaging, a rectal exam for anal gland masses, and lymph node checks.

• Treating the underlying cause, such as cancer therapy, removing a parathyroid tumor, or managing Addison’s or kidney disease
• Intravenous fluids and medications that help the kidneys flush calcium out when levels are high
• Bisphosphonates or other calcium-lowering drugs in some cases
• Diet changes for cats with idiopathic hypercalcemia, such as higher-fiber or kidney-support foods, sometimes with medication

Steroids can lower calcium but may hide lymphoma and make it harder to diagnose, so vets usually avoid them until cancer has been ruled out.

Prognosis and Cost Guidance

The outlook depends entirely on the cause. Dogs with a benign parathyroid tumor often do very well after surgery, while cancer-related hypercalcemia carries a more guarded outlook. In the US, the diagnostic workup with specialized blood tests and imaging often costs several hundred to over a thousand dollars before treatment begins.

Practical Tips for US Pet Owners

• Keep rodent baits, vitamin D supplements, and prescription skin creams well out of reach.
• Mention any change in thirst or urination to your vet, even if your pet seems fine otherwise.
• Ask for routine senior blood work, which often catches high calcium early.
• Find general and internal-medicine-capable practices through veterinary clinic listings.

Key Takeaways

• Hypercalcemia means too much calcium in the blood and is a clue to another problem.
• In dogs, cancer is a leading cause; in cats, idiopathic hypercalcemia is most common.
• Treatment targets the underlying cause, and fast action protects the kidneys.

FAQ

Can diet cause high calcium?
Rarely on its own, but over-supplementing calcium or vitamin D can. Complete and balanced commercial diets do not normally cause it.

Is mild hypercalcemia an emergency?
Not usually, but it should be rechecked and investigated soon. Very high levels or known poisoning need urgent care.

What is a normal calcium level?
Reference ranges differ by lab and species, so your vet will interpret results against the lab’s own normal range.