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 dogs – 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 dogs are at risk for mineralization of their soft tissues, including their kidneys.
Emergency Treatment

Intravenous administration of fluids, usually physiologic salt solution, facilitates the excretion of calcium in the urine.

Administration of the diuretic drug [furosemide (Lasix®) also facilitates excretion of sodium and calcium in the urine.

Cortisone-like drugs (prednisone) can limit bone release of calcium, decrease intestinal absorption of calcium, and increase excretion of calcium in the urine. These drugs can have a direct toxic effect on some cancer cells, specifically, malignant lymphocytes, and, if at all possible, they should not be given until a definitive diagnosis has been made.

A new class of drugs called diphosphonates can be given to decrease bone release of calcium.

Many other drugs (some with potentially serious adverse effects) may be required to treat dogs with refractory hypercalcemia. Examples include mithramycin, calcitonin, and ethylenediametetraacetic acid (EDTA).

Above all it is crucial to treat the underlying disease process that is causing the hypercalcemia.