Causes of high calcium in dogs and the role of nutrition

Finding abnormally high levels of calcium in a dog’s blood (hypercalcemia) can be a sign of an underlying health issue. Calcium is necessary for many bodily systems, including the musculoskeletal, gastrointestinal (GI), and endocrine systems. Calcium levels are normally tightly regulated by the body’s internal systems, so if levels are higher than the healthy range, something may be wrong with one or more of those bodily systems. If you have a dog, read on to learn about:

• Why elevated calcium levels can be dangerous
• Health issues that can cause hypercalcemia in dogs
• Clinical signs associated with high calcium levels
• How much calcium dogs need in their diet

Various health issues can cause hypercalcemia in dogs, including renal failure, Addison’s disease, primary hyperparathyroidism, and some malignant cancers. Hypercalcemia can also occur after ingestion of cholecalciferol rodent poisons. Idiopathic hypercalcemia in dogs, which means calcium levels are elevated with no identifiable cause, is very rare. Hypercalcemia is not caused by ingesting too much calcium in the diet, as the body normally has mechanisms in place to keep calcium levels stable. However, nutrition can play an important role in treating the underlying illness that’s disrupting calcium regulation.

Elevated blood calcium levels, or hypercalcemia, is a clinical finding seen on a dog’s blood work that indicates something may be wrong. Hypercalcemia is not a disease itself, but it occurs with many health issues and can be very serious. A high calcium level does not indicate a dog is eating too much calcium in their diet. Instead, it’s due to a health issue disrupting the body’s ability to keep blood calcium levels within a healthy range.

Many parts of the body work together to keep calcium levels tightly regulated. Because of this, a clinical finding of elevated levels is more complicated than a dog simply eating too much calcium. Instead, elevated calcium levels can indicate a problem in one or more parts of the body that regulate them, including:

• Bones
• GI tract
• Kidneys
• Hormones

Diagnosing the cause of hypercalcemia involves identifying where the disruption is occurring in the body’s calcium regulation system.

The role of calcium in a dog’s body

Calcium in the body is used in:

• Bone construction
• Muscle contraction, including the beating of the heart
• The movement of food and waste through the digestive tract
• The activation of various enzymes that regulate multiple bodily functions

When calcium levels in the blood are too low, the body can release stored calcium from the bones to restore balance. This process is a normal part of calcium regulation and is tightly controlled by hormones. In healthy dogs, once blood calcium levels return to normal, any excess calcium can be returned to the bones, keeping the skeletal system strong and stable.

However, in dogs with certain diseases, such as cancer or parathyroid gland disorders, these hormonal signals can become disrupted, causing the body to release too much calcium from the bones. Over time, this can weaken the bones and increase the risk of fractures.

In healthy dogs, the kidneys also play an important role in calcium balance by filtering out and excreting excess calcium through the urine. But when calcium levels are abnormally high due to disease, the kidneys may struggle to keep up, contributing to further health complications.

The processes by which calcium is stored and released are controlled by two hormones: the parathyroid hormone (PTH) and calcitriol (vitamin D). Disruption in the normal function of these calcium-regulating hormones can contribute to elevated calcium levels. PTH is produced by the parathyroid gland, found in the neck, and calcitriol is produced by the kidneys, so diseases in either of these locations may interfere with calcium regulation.

“The most common cause of hypercalcemia in dogs is some type of malignant cancer somewhere in the body,” explains Dr. Jo Myers, a veterinarian on the Vetster platform. “This is known as hypercalcemia of malignancy.” Cancers that can lead to hypercalcemia of malignancy include:

• Lymphoma
• Anal sac adenocarcinoma
• Mammary tumors
• Multiple myeloma

Other medical conditions that can cause hypercalcemia in dogs include:

• Kidney failure
• Addison’s disease
• Primary hyperparathyroidism
• Vitamin D toxicosis (from cholecalciferol rodent poisons)

Idiopathic hypercalcemia, or hypercalcemia with no identifiable cause, is very rare in dogs. In most cases, high calcium on a blood test is a sign of an underlying medical issue, often something serious, like cancer. When a dog comes to the vet for vague or nonspecific signs of illness, and hypercalcemia is the main abnormality in their blood work, it means a thorough diagnostic process is needed to look for hidden diseases. While it may seem like a minor lab finding or something connected to the dog’s diet, an elevated calcium level is actually a serious concern and identifying the underlying cause isn’t always straightforward.

Is my dog at risk for hypercalcemia?

Most healthy dogs are not at risk for hypercalcemia. When elevated calcium levels are found, they are almost always caused by an underlying medical condition, not by diet. Dogs with certain health problems are more likely to develop hypercalcemia because the condition interferes with the body’s ability to regulate calcium levels.

Conditions that may put a dog at higher risk for hypercalcemia include:

• Cancer or tumors
• Kidney disease or failure
• Addison’s disease

Detecting high calcium on blood work often leads to further diagnostic testing to identify the underlying cause, which is essential for determining the right treatment plan. If your dog has a condition that puts them at higher risk, it’s important to work closely with a veterinarian to determine the next steps. Your vet may recommend routine monitoring or special diagnostic tests.

While diet is not a cause of high calcium levels, it can be an important part of managing the underlying illness that’s disrupting calcium regulation. For example, dogs with kidney disease or certain types of cancer may benefit from prescription diets designed to support organ function or overall health. Because these dietary changes need to be tailored to the specific condition and health status of your dog, you should never change your dog’s diet or add supplements without veterinary guidance.

Clinical signs of hypercalcemia vary depending on the severity of hypercalcemia and the progression of the underlying disease. Up to one-third of dogs with hypercalcemia show no obvious symptoms. When clinical signs are present, they may include:

• Lethargy
• Frequent urination
• Excessive thirst
• Loss of appetite
• Vomiting
• Constipation
• Muscle tremors
• Seizures
• Loss of consciousness

Additional symptoms may appear depending on the underlying disease causing the elevated calcium levels. Many of these signs — such as increased thirst, vomiting, and lethargy — are shared by other common health problems in dogs.

Many dogs with hypercalcemia show no symptoms at all when it’s first detected, which is concerning because the most common cause is early-stage malignant cancer. Often, the condition is only discovered through routine blood work. Because of this, a finding of hypercalcemia, even in an otherwise healthy-appearing dog, warrants a thorough investigation by a veterinarian to determine the underlying cause and the appropriate treatment.

Treatment of hypercalcemia in dogs primarily focuses on treating the underlying health issue causing it. While diet is not typically the cause of high calcium levels in dogs, special diets for specific health conditions may be beneficial for the long-term management of some of the diseases associated with hypercalcemia, especially cancer or kidney failure.

Therapeutic diets for kidney disease may help to improve a patient’s quality of life by slowing disease progression and improving symptoms. In some patients with cancer, special diets can be used to try to improve immune function, manage weight loss and muscle wasting, reduce inflammation, and alleviate vomiting and poor appetite. Virtual vet visits are a great way to talk to a veterinarian about your dog’s dietary history, diagnosis, and symptoms to help determine if a therapeutic diet may be beneficial.

Other medical treatment options for dogs with hypercalcemia

Additional treatment for hypercalcemia to help lower calcium levels while the underlying problem is being treated may involve:

• Steroids
• IV fluid therapy
• Diuretics

Treatment options vary widely depending on the underlying cause of the hypercalcemia. Prognosis also varies between conditions and patients.

Dogs require calcium to maintain healthy bones, teeth, nerve function, and muscle contraction. Fortunately, the body has tightly regulated systems (primarily involving the parathyroid hormone, vitamin D, and the kidneys) that help maintain normal blood calcium levels regardless of fluctuations in dietary intake. However, these regulatory systems are not foolproof, especially in growing puppies, and it’s important to avoid providing either too little or too much calcium.

The specific amount of dietary calcium a dog needs depends on their age, size, breed, and underlying health issues. Growing puppies and lactating mothers require more calcium than other dogs. Choosing a dog food with an AAFCO statement of nutritional adequacy on the label and feeding it as directed is the best way to ensure your dog is eating the right amount of calcium. If you’re concerned about inadequate amounts of calcium in your dog’s diet, it’s best to talk to a veterinarian before supplementing.

Ingesting excessive calcium can lead to health problems in puppies, especially if they’re given calcium supplements on top of a balanced diet or fed an unbalanced homemade diet. Puppies have less ability to regulate excess calcium compared to adults, which puts them at risk for complications. While true hypercalcemia is uncommon, too much dietary calcium during growth, especially in large-breed puppies, can contribute to bone and joint disorders, such as abnormal skeletal development. On the other side of the equation, calcium deficiency can result in rickets, a condition where bones fail to mineralize properly, leading to pain, deformities, and stunted growth.

The ratio of calcium to phosphorus in a dog’s diet is just as important as the amount of calcium a dog ingests. A diet formulated to meet AAFCO standards for healthy dogs typically has a 1:1 calcium to phosphorus ratio. Some diets for specific health issues may have an altered ratio. It’s very important to talk to a vet before giving a dog calcium supplements or changing diets. An online vet can address concerns about your dog’s calcium levels, recommend an appropriate diet, and offer guidance on what to do next.

What causes high calcium levels in dogs?

High calcium levels in dogs are almost always the result of an underlying medical condition disrupting the body’s ability to regulate calcium rather than an excess of calcium in their diet. The most common causes include certain types of cancer, kidney disease, Addison’s disease, and parathyroid gland disorders. While it’s a common misconception, feeding a healthy adult dog too much calcium is not a typical cause of hypercalcemia.

How do vets treat high calcium levels in dogs?

High calcium levels in dogs are usually caused by an underlying medical issue, such as chronic kidney disease, cancer, Addison’s disease, or vitamin D toxicosis from consuming certain types of rat poison. Treatment focuses on resolving the underlying cause of hypercalcemia, with supportive therapies used to lower calcium levels in the short term if needed.

Can dog food cause high levels of calcium?

A dog’s body has multiple methods for keeping calcium at a healthy level, regardless of what they eat. Instead of being caused by a dog’s diet, high levels of calcium (hypercalcemia) is usually caused by an underlying medical condition, such as kidney disease or cancer, that alters the body’s ability to regulate calcium levels. Growing puppies are less able to regulate calcium levels than adults, so they are more at risk of hypercalcemia from oversupplementing calcium in the diet. You should always talk to a veterinarian before adding a calcium supplement or changing your dog’s diet.

Disclaimer: This article, its content, and its related references do not constitute veterinary advice and should not be considered a substitute for veterinary care. If your pet is showing any symptoms that could indicate a medical emergency, please seek immediate emergency care.