If Your Dog Is Drinking Excessive Water and Showing Lethargy — Causes of Hypercalcemia and When to Visit the Vet

EndocrineDiseasesMeongsiljang Veterinary Advisory Board

Canine hypercalcemia is an endocrine disorder characterized by abnormally elevated blood calcium levels, which can lead to symptoms such as excessive thirst, constipation, and lethargy. Early diagnosis and identification of the underlying cause are essential.

Canine Hypercalcemia Is an Endocrine Disorder Characterized by Elevated Blood Calcium Levels

A veterinarian and a puppy reviewing blood test results that indicate hypercalcemia

Hypercalcemia in dogs is an endocrine disorder characterized by abnormally high blood calcium levels, and it is more commonly reported in middle-aged to senior dogs. Calcium is an essential mineral for normal nerve and muscle cell excitability and conduction, but excessive levels can strain multiple organs, including the kidneys, heart, and gastrointestinal tract. If left chronic, calcium can deposit in the renal tubules and other tissues, leading to gradual mineralization and damage, making early detection crucial. Identifying the underlying cause and initiating treatment early significantly supports long-term health management. Regular blood tests to monitor calcium levels are the ideal approach for ongoing care.

Major Causes Include Cancer, Hyperparathyroidism, and Vitamin D Toxicity

- Malignant hypercalcemia: Malignant tumors such as lymphoma, anal sac adenocarcinoma, and multiple myeloma can elevate blood calcium levels. - Hyperparathyroidism: Excessive secretion of parathyroid hormone (PTH) disrupts calcium metabolism. - Vitamin D toxicity: Excessive vitamin D activity from diet or cholecalciferol-containing rodenticides increases intestinal calcium absorption, leading to hypercalcemia. - Kidney disease: Impaired calcium excretion and metabolism can disrupt calcium balance. - Hormonal imbalances, such as hypoadrenocorticism (Addison’s disease): These conditions can also be underlying causes, making accurate differential diagnosis the first step toward effective treatment.

A diagram explaining calcium regulation disorders in a dog's endocrine system

Major Symptoms Include Excessive Thirst, Constipation, and Lethargy

The most common signs of hypercalcemia in dogs are excessive thirst (polydipsia) and frequent urination (polyuria). This happens because high calcium levels interfere with the action of antidiuretic hormone (ADH) in the renal tubules, making it difficult for the body to regulate fluid balance. Other frequent symptoms include constipation, loss of appetite, lethargy, vomiting, and weight loss. In severe cases, muscle weakness, irregular heart rhythms (arrhythmias), and kidney damage can occur. Since these symptoms often develop gradually and can be easily overlooked by pet owners, close monitoring is essential.

Excessive thirst: Your dog will drink noticeably more water than usual.

Frequent or increased urination: Your dog will need to go to the bathroom more often or produce larger volumes of urine.

Constipation: Reduced motility of the smooth muscles in the gastrointestinal tract makes bowel movements difficult.

Lethargy: Your dog will show little energy, remaining sluggish and inactive throughout the day.

Decreased appetite: Your dog may refuse treats or eat significantly less than normal.

A lethargic puppy with hypercalcemia and its water bowl

Seek Immediate Veterinary Care for Severe Symptoms or Suspected Kidney Dysfunction

If your dog experiences severe vomiting, persistent lethargy and weakness, or dehydration due to excessive urination, seek veterinary care immediately. Severe hypercalcemia can cause calcium deposits in the renal tubules, leading to a rapid decline in kidney function or cardiac arrhythmias. Dogs with pre-existing kidney disease are at particularly high risk. In emergency situations, treatment involves intravenous fluid therapy alongside interventions to lower calcium levels.

Diagnosis Is Confirmed Through Blood Tests and Imaging Studies

Canine hypercalcemia is diagnosed when total blood calcium levels exceed 12.0 mg/dL. To improve diagnostic accuracy, ionized calcium levels are also measured. Additional tests, including kidney and liver function panels, hormone assays, and imaging studies such as ultrasound or X-rays, are performed to identify the underlying cause. If lymphoma or parathyroid tumors are suspected, a biopsy may be necessary. Thorough diagnostic testing is essential, as treating without an accurate diagnosis can easily lead to missing the root cause.

A veterinarian performing a blood test on a puppy

Treatment Focuses on Addressing the Underlying Cause and Regulating Calcium Levels

Treatment for hypercalcemia depends on the underlying cause. If cancer is responsible, chemotherapy or surgery may be necessary. For hyperparathyroidism, surgical removal of the parathyroid glands is the primary treatment. In acute cases, intravenous fluids are administered, along with diuretics or steroids to lower calcium levels. In severe cases, bisphosphonate medications may also be used. Throughout treatment, it’s essential to carefully manage hydration and electrolyte balance. The duration of treatment varies depending on the cause and the patient’s condition.

A puppy receiving an intravenous injection

Home Care Emphasizes Hydration and Dietary Management

- Maintain hydration: Dogs with hypercalcemia are at high risk of dehydration, so encourage them to drink water consistently. - Provide a low-calcium diet: Follow your veterinarian’s dietary recommendations to reduce calcium intake. - Limit vitamin D: Strictly avoid supplements and foods high in vitamin D. - Moderate exercise: Excessive activity can be burdensome, so keep exercise at an appropriate level. - Regular check-ups: Blood tests are recommended every 1 to 3 months to monitor calcium levels. - Medication precautions: Always administer medications related to hypercalcemia strictly under your veterinarian’s guidance.

Low-calcium food and water bowl for managing hypercalcemia

Breeds Predisposed to Hyperparathyroidism Require Special Attention

Hyperparathyroidism has a known predisposition in certain breeds, with the Keeshond being particularly prone to primary hyperparathyroidism. Because predisposed breeds are at a relatively higher risk of hypercalcemia, early detection through regular blood tests is essential. Additionally, senior dogs may struggle to regulate calcium due to declining kidney function, requiring extra vigilance. Early diagnosis and consistent management can help prevent complications.

Reviewed by a veterinarian

Dr. Tony — Punnawat Phongkittirak

Veterinarian

A veterinarian who majored in veterinary medicine at Khon Kaen University, Thailand, and completed the IVSA program at North Carolina State University in the United States. Drawing on clinical experience at animal hospitals, he works in the pet healthcare field and is dedicated to building a digital care environment that connects pet parents with veterinarians.

Frequently Asked Questions

Can hypercalcemia in dogs be treated?

With accurate diagnosis and appropriate treatment, most cases improve significantly. If cancer is the underlying cause, the prognosis may differ, but primary hyperparathyroidism can be resolved through parathyroidectomy.

Can hypercalcemia be genetic?

Primary hyperparathyroidism has been reported to have a breed predisposition in certain dogs. The Keeshond is notably known to be predisposed to this condition. If you’re concerned, discuss regular blood tests and calcium level monitoring with your veterinarian.

Can hypercalcemia be resolved through dietary management alone?

Dietary management can help, but if the underlying cause is cancer or a hormonal imbalance, it won’t be enough on its own. A veterinary diagnosis and treatment are essential.

What tests are needed if hypercalcemia develops?

We’ll need blood tests (total calcium, ionized calcium), kidney and liver function tests, hormone levels like PTH, and imaging such as ultrasound or X-rays. These will help us identify the underlying cause.

Can hypercalcemia recur?

Even after treatment, the underlying cause may persist or the condition may recur. This is especially true for cancer or parathyroid issues, where regular check-ups and ongoing management are essential. It’s best to work with your veterinarian to develop a long-term care plan.

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References

[1] Joao Felipe de Brito Galvao et al. (2023) Calcium Disorders in Small Animals. In: Small Animal Critical Care Medicine, 3rd Edition. Elsevier.

[2] Blackwell's Five-Minute Veterinary Consult Clinical Companion, Small Animal Toxicology, 3rd Edition. (2022). Calcium disorders and toxicities.

[3] Messinger JS, Windham WR, Ward CR. (2005). Ionized hypercalcemia in dogs: a retrospective study of 109 cases (1998–2003). Journal of Veterinary Internal Medicine, 19(2), 234–240.