Paraneoplastic hypercalcemia of malignancy

Apocrine anal sac adenocarcinoma, lymphoma, thymoma, carcinoma, others

Primary hyperparathyroidism

Adenoma, hyperplasia, carcinoma

Renal failure

Acute or chronic

Medications

Thiazide diuretics, vitamin D toxicosis, calcium supplementation, vitamin A toxicosis

Granulomatous disease

Fungal disease, panniculitis, injection reaction

Nonparathyroid endocrine

Hypoadrenocorticism, thyrotoxicosis

Skeletal disease

Osteomyelitis, osteoporosis, hypertrophic osteodystrophy

Toxic

House plants, rodenticides, raisin/grape 

Transient

Associated with hemoconcentration, hyperproteinemia

Idiopathic

Cats only

Spurious

Lab error, tube or sample error

Nonpathologic

Postprandial, young age, lipemia