A high level of calcium (hypercalcemia) in a dog may indicate a serious underlying condition. On the other hand it may be fairly minor. For this reason it must be investigated by a qualified veterinarian.
Amazingly a high calcium level may be measure if a blood sample is taken soon after the dog has eaten owing to a high blood lipid level. If during processing the blood sample undergoes hemolysis the release of hemoglobin also causes a high calcium level.
A dog with hypercalcemia typically suffers from loss of appetite, thirst, increased frequency of urination, vomiting, constipation, lethargy and weakness. Severe cases may cause seizures. All these signs are non-specific and a veterinarian will require further tests and a full medical history to obtain a diagnosis
Possibly the most common cause of hypercalcemia in dogs is dehydration. A dehydrated dog normally recovers after the administration of intravenous or subcutaneous fluids and its blood calcium resumes its normal level.
Another cause of hypercalcemia is Vitamin D toxicosis. There are a number of everyday sources of Vitamin D that can poison a dog. Some rat poisons contain the vitamin as do some topical ointments such as psoriasis ointments which contain calcipotriene. Some plants are rich in the vitamin and dogs occasionally ingest plant material. These plants include day-blooming Jessamine (Cestrum diurnum), the South American egg-plant (Solanum malacoxylon) and Yellow Oat-grass (Trisetum flavescens).
Some cancers also lead to hypercalcemia in dogs. Amongst others, thyroid, nasal or mammary gland adenocarcinomas, squamous cell carcinoma, anal gland cancer, and lymphosarcomas can all lead to high calcium levels.
A benign tumor, known as an adenoma, of the parathyroid gland can cause primary hyperparathyroidism (over-activity of that gland) and a rise in blood calcium. Faulty nutrition may also cause over-activity of the parathyroid gland.
Other causes of the condition include chronic or acute kidney failure, hypoadrenocorticism, (Addison's disease), osteomyelitis (bone infection) and granulomatous diseases such as the fungal disease blastomycosis. In addition some healthy young dogs develop the condition naturally.
While treatment of the underlying condition is essential, hypercalcemia is of itself a dangerous condition. High calcium levels in excess of 15 milligrams per deciliter have an adverse effect on many organs including kidneys, heart, nervous system and the gastrointestinal tract. Damage to the soft tissues occurs when the calcium is deposited within in them.
Emergency treatment of hypercalcemia requires intravenous fluids to encourage excretion of calcium in the urine. A diuretic such as furosemide (Lasix) helps this excretion. Intravenous sodium bicarbonate decreases blood calcium levels Cortisones such as Prednisone prevent release of calcium from bones and increase its excretion. However, cortisones may exacerbate certain cancers and their use in dogs with such conditions may be contraindicated. Other drugs that may be of use in the treatment of hypercalcemia include mithramycin, calcitonin, and ethylene-diame-tetra-acetic acid (EDTA). A recently released class of drugs, the diphosphonates, decreases the bone release of calcium.