Hypercalcemia in Dogs: Causes, Signs, Diagnosis, and Treatment

Updated September 21, 2026. Fact-checked against veterinary sources; review by a licensed veterinarian is in progress. See our editorial policy.

Quick answer: Hypercalcemia means a dog has too much calcium in the blood. It’s often found on routine bloodwork before any signs appear, but it can also cause increased thirst and urination, a poor appetite, vomiting, and weakness. In dogs, the most common causes are certain cancers (especially lymphoma and anal sac tumors), overactive parathyroid glands, kidney disease, and Addison’s disease. Vitamin D poisoning is a less common but urgent cause. Because the causes range from mild to serious, any high calcium result should be worked up by your veterinarian rather than ignored.

What is hypercalcemia?

Calcium does far more than build bones. It helps muscles contract, nerves send signals, and blood clot. The body keeps blood calcium in a tight range using parathyroid hormone, vitamin D, and the kidneys. Hypercalcemia happens when something pushes calcium above that range and keeps it there.

Vets look at two numbers: total calcium, which is on most routine blood panels, and ionized calcium, the active form. Ionized calcium gives the clearest picture of whether a dog truly has hypercalcemia, so a high total calcium is usually followed by an ionized calcium test.

Signs of high calcium in dogs

Many dogs have no obvious signs, and hypercalcemia is increasingly discovered on pre-anesthetic or annual bloodwork. When signs do appear, they can include:

Drinking and urinating more than usual
Reduced appetite
Vomiting
Constipation
Weakness, tiredness, or seeming depressed
In some dogs, bladder stones, or signs of the underlying disease such as enlarged lymph nodes or a lump near the anus

Very high calcium, or calcium that rises quickly, tends to cause more severe signs. Over time, high calcium can also damage the kidneys, which is one reason vets don’t leave it untreated.

What causes hypercalcemia in dogs?

Cancer (hypercalcemia of malignancy). This is the most common cause in dogs. Lymphoma, especially T-cell lymphoma, and apocrine gland anal sac adenocarcinoma are the classic culprits, though many other cancers can do it. The tumor releases substances, most often parathyroid hormone-related protein (PTHrP), that raise blood calcium.
Primary hyperparathyroidism. A usually benign tumor of a parathyroid gland overproduces parathyroid hormone. Up to a third of dogs with this condition have no signs when it’s diagnosed.
Kidney disease. Kidney problems can raise calcium, and high calcium can also harm the kidneys, so the two can feed each other.
Addison’s disease (hypoadrenocorticism). Calcium is elevated in a significant share of dogs with Addison’s, but it usually resolves once the Addison’s is treated.
Vitamin D toxicity. Less common but an emergency. Sources include some rat and mouse poisons (cholecalciferol), human psoriasis creams containing calcipotriene or calcipotriol, and vitamin D supplements.
Other causes include certain fungal infections and other granulomatous diseases, and bone disease. Young, growing dogs can have mildly higher calcium that’s normal for their age.

When it’s an emergency

Call your veterinarian or an emergency clinic immediately if you think your dog may have eaten rat or mouse poison, chewed a tube of psoriasis cream, or gotten into vitamin D supplements, even if they seem fine. Signs of vitamin D poisoning can take a day or more to appear, and early treatment matters. You can also call the ASPCA Animal Poison Control Center at 888-426-4435 (a consultation fee may apply). Also seek urgent care if a dog with known high calcium stops eating, vomits repeatedly, becomes very weak, or stops urinating.

How vets find the cause

Finding the cause is the key step, because treatment depends on it. Your veterinarian may:

Repeat the calcium test and measure ionized calcium
Do a careful physical exam, including feeling the lymph nodes and a rectal exam to check the anal sacs
Run a hypercalcemia panel measuring parathyroid hormone, PTHrP, and vitamin D levels
Take chest X-rays and an abdominal ultrasound to look for tumors
Use a neck ultrasound to look for an enlarged parathyroid gland
Sample enlarged lymph nodes or other masses
Test for Addison’s disease and check kidney function

Your vet may hold off on steroids until lymphoma has been ruled out, because steroids can mask lymphoma and make it harder to diagnose.

Treatment

Hypercalcemia resolves only when the underlying cause is treated, but vets often lower calcium at the same time to protect the kidneys. Depending on the situation, treatment may include:

IV fluids to help the kidneys flush out calcium
Diuretics that increase calcium loss in the urine
Steroids, once the cause is known
Other calcium-lowering drugs, such as bisphosphonates, for more severe or persistent cases
Treating the cause, for example chemotherapy for lymphoma, surgery for an anal sac or parathyroid tumor, managing Addison’s disease, or treating vitamin D poisoning

Outlook

The outlook depends almost entirely on the cause. Dogs with a benign parathyroid tumor often do very well once the tumor is removed or treated. Hypercalcemia from Addison’s usually resolves with treatment. When cancer is the cause, the prognosis depends on the type and stage of cancer and how it responds to treatment. Your veterinarian, and in some cases a veterinary internist or oncologist, can give you a realistic picture for your dog.

Frequently asked questions

My dog’s calcium was slightly high on routine bloodwork. Should I worry?

Not necessarily, but don’t ignore it. A single slightly high result can have simple explanations, and young dogs normally run a little higher. Your vet will usually recheck it and measure ionized calcium before deciding on next steps.

Does high calcium in dogs always mean cancer?

No. Cancer is the most common cause, but parathyroid disease, kidney disease, Addison’s disease, and toxins are all possible, which is why testing to find the cause matters.

Should I change my dog’s diet?

Don’t change the diet or stop supplements on your own before talking with your vet. If your dog takes any supplement containing vitamin D or calcium, bring the bottle to the appointment.

Sources

This article is for general education and is not a substitute for care from your own veterinarian. Learn about The Pet Vet and our editorial policy.