Hypercalcemia
Hypercalcemia
Also known as: Elevated blood calcium, High calcium
Hypercalcemia
Also known as: Elevated blood calcium, High calcium
In short
Hypercalcemia is an abnormally high level of calcium in a dog or cat's blood. This metabolic condition can cause severe damage to the kidneys, heart, and nervous system. Learn about the symptoms, underlying causes, diagnostic tests, and treatment options.

TL;DR. Hypercalcemia is a serious medical condition where blood calcium levels rise too high, potentially damaging your pet's kidneys, heart, and nervous system if left untreated.

Hypercalcemia can affect both dogs and cats, requiring prompt veterinary diagnosis.
Calcium is a vital mineral that plays a crucial role in almost every major function in your pet's body. It is responsible for transmitting nerve impulses, contracting muscles (including the heart), clotting blood, and maintaining strong bones. Because calcium is so important, the body tightly regulates its levels using a complex network of hormones, primarily involving the parathyroid glands, the kidneys, the intestines, and the bones.
When this regulatory system fails and calcium levels in the bloodstream rise abnormally high, the condition is known as hypercalcemia. Rather than being a primary disease on its own, hypercalcemia is typically a warning sign of a serious underlying medical issue. When calcium levels remain elevated, the mineral acts as a toxin to various organ systems, leading to widespread dysfunction.
One of the most significant concerns with hypercalcemia is its impact on the kidneys and the central nervous system. As noted in a prominent small animal critical care manual:
"The consequences of hypercalcemia can be severe and affect multiple body systems including the central nervous syst" — Small Animal Critical Care Medicine
When calcium levels are excessively high, the kidneys lose their ability to conserve water, leading to dehydration and potential kidney failure. If both calcium and phosphorus levels are elevated, they can bind together and form hard mineral deposits within the kidney tissues, a process called nephrocalcinosis. This can cause irreversible damage to the kidneys, making prompt veterinary intervention essential.
Hypercalcemia can be triggered by a wide variety of underlying conditions. In dogs and cats, the most common causes include:
Certain breeds carry genetic risks for developing diseases that cause hypercalcemia. For instance, the Keeshond has a well-documented genetic predisposition to primary hyperparathyroidism, while Siamese cats also show an increased risk for developing elevated blood calcium levels.
The clinical signs of hypercalcemia can vary widely depending on how high the calcium levels are and how quickly they rose. Because calcium affects multiple body systems, the symptoms can appear diverse and non-specific.

Increased thirst and urination are classic early warning signs of elevated blood calcium.
If your pet is showing signs of severe lethargy, persistent vomiting, or irregular breathing, these are red-flag emergencies that require immediate veterinary care. High calcium levels can also cause dangerous changes to the heart's rhythm, as detailed in a leading critical care reference:
"Bradycardia may be detected on physical examination, and electrocardiographic (ECG) monitoring may reveal a prolonged PR interval, widened QRS complex, shortened QT interval, shortened or absent ST segment, and a widened T wave. Bradyarrhythmias may progress to complete heart block, asystole, and cardiac arrest in severely affected animals." — Small Animal Critical Care Medicine
Diagnosing hypercalcemia begins with a thorough physical examination and routine blood work. A standard chemistry panel measures "total serum calcium," which includes calcium bound to proteins in the blood. However, this does not always reflect the amount of active calcium available to the tissues.
To get an accurate diagnosis, your vet will perform the gold-standard test:
Once hypercalcemia is confirmed, the vet must determine the underlying cause. This typically involves several specialized tests:

Ionized calcium testing is the gold standard for diagnosing hypercalcemia.
Determining whether kidney damage is the cause or the result of high calcium is one of the greatest diagnostic challenges in veterinary medicine. As noted in a leading veterinary internal medicine reference:
"Prolonged hypercalcemia, especially in conjunction with concurrent high-normal to increased serum phosphorus concentration, can also cause nephrocalcinosis and exacerbate renal insufficiency and azotemia. Determining whether the renal failure is primary or secondary in a dog with hypercalcemia, hyperphosphatemia, and azotemia poses an interesting diagnostic challenge..." — Internal Medicine
Your vet will carefully evaluate all of these parameters to map out the correct treatment plan.
Treatment for hypercalcemia is two-fold: it must address the immediate danger of high calcium levels (supportive therapy) while simultaneously targeting the underlying cause. According to a leading internal medicine textbook:
"Medical therapy should be directed at eradicating the underlying cause of the hypercalcemia. Supportive therapy to decrease the serum calcium concentration to less toxic levels is indicated if clinical signs are severe, if serum calcium concentration is greater than 17 mg/dL (dog) or 16 mg/dL (cat), if serum ionized calcium is greater than 1. 8 mmol/L (dog) or 1. 7 mmol/L (cat)..." — Internal Medicine
Because hypercalcemia is a metabolic state rather than a primary disease, long-term prognosis data for the condition itself is limited. The overall outlook for your pet depends almost entirely on the underlying cause.
If the high calcium is caused by a benign parathyroid tumor (common in Keeshonds), surgical removal of the affected gland carries an excellent prognosis, and most pets return to a normal life. If the cause is an aggressive cancer, the prognosis is much more guarded. If the hypercalcemia was prolonged and caused severe kidney damage (nephrocalcinosis), your pet may require lifelong management for chronic kidney disease.
Most cases of hypercalcemia cannot be prevented because they are caused by internal diseases like cancer or autoimmune conditions. However, you can prevent toxicity-induced hypercalcemia by keeping potential toxins out of your pet's reach. This includes rodenticides containing cholecalciferol, human psoriasis creams, and vitamin D supplements.
For breeds at risk, regular senior wellness blood screens—including ionized calcium measurements—can help catch elevated calcium levels early, before they cause irreversible damage to the kidneys or heart.
If you notice your pet is drinking and urinating significantly more than usual, schedule an appointment with your vet.
You must seek emergency veterinary care immediately if your pet exhibits any of the following red flags:
If you own a Keeshond, be aware that this breed has an autosomal dominant genetic predisposition to primary hyperparathyroidism. This means if a parent carries the gene, there is a high likelihood their offspring will develop the condition. Genetic testing and routine blood screening are highly recommended for this breed.
If you own a Siamese cat, your pet has an increased risk of developing hypercalcemia. While the exact genetic mechanism is still unknown, regular wellness blood work is an important tool to monitor their calcium levels as they age.
Treatment must be prescribed by a licensed veterinarian based on your pet. Specific drug doses are intentionally not shown here.
Hypercalcemia is an abnormally high level of calcium in a dog or cat's blood. This metabolic condition can cause severe damage to the kidneys, heart, and nervous system. Learn about the symptoms, underlying causes, diagnostic tests, and treatment options.
Anorexia、Dehydration、Lethargy、Muscle weakness、Polydipsia、Polyuria、Vomiting、Constipation
Ionized calcium measurement、Serum PTH concentration、Serum PTHrP concentration、Total serum calcium measurement
Treatment must be prescribed by a licensed veterinarian based on your pet. Specific drug doses are intentionally not shown here.
This article is for general education and is not a substitute for professional veterinary advice. If your pet is unwell, please consult a veterinarian.
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