What Are The Signs Of Hypercalcemia In Cats?

Understanding Hypercalcemia in Cats: Causes, Symptoms, Diagnosis, and Treatment. Hypercalcemia in cats is a condition characterized by elevated calcium levels in the bloodstream. While calcium is essential for various bodily functions, excessive levels can lead to serious health complications. Understanding the causes, symptoms, diagnosis, and treatment options for hypercalcemia is crucial for cat owners to ensure their feline companions receive appropriate care.

What Is Hypercalcemia?

Hypercalcemia occurs when a cat’s calcium levels exceed the normal range of approximately 8.5 to 11.0 mg/dL. Persistent hypercalcemia can affect multiple organ systems, leading to kidney damage, cardiovascular issues, and neurological problems. The condition can be either primary or secondary to an underlying disease.

Causes of Hypercalcemia in Cats

Hypercalcemia in cats can arise from various medical conditions, including:

1. Idiopathic Hypercalcemia – The most common cause of hypercalcemia in cats, particularly in middle-aged and older felines. The exact cause remains unknown.
2. Chronic Kidney Disease (CKD) – Impaired kidney function can disrupt calcium and phosphorus balance, leading to hypercalcemia.
3. Cancer (Neoplasia) – Lymphoma, squamous cell carcinoma, and other malignancies can lead to elevated calcium levels.
4. Primary Hyperparathyroidism – A rare condition where the parathyroid glands produce excessive parathyroid hormone (PTH), increasing calcium absorption.
5. Vitamin D Toxicity – Ingestion of excessive vitamin D supplements, rodenticides, or certain human medications can cause dangerously high calcium levels.
6. Granulomatous Diseases – Infections or inflammatory conditions, such as fungal infections, can contribute to calcium imbalances.
7. Addison’s Disease – Hypoadrenocorticism, a disorder of the adrenal glands, can be associated with hypercalcemia.

Symptoms of Hypercalcemia in Cats

The clinical signs of hypercalcemia vary depending on the severity and underlying cause. Common symptoms include:

• Increased thirst (polydipsia) and urination (polyuria)
• Lethargy and weakness
• Decreased appetite (anorexia)
• Vomiting
• Constipation
• Weight loss
• Muscle tremors or twitching
• Depression or behavioral changes
• Increased risk of bladder stones due to excess calcium

Additional and Clinical Signs Of Hypercalcemia In Cats

The clinical signs of hypercalcemia depend on both its severity and the underlying cause. They may be subtle at first but become more pronounced as calcium levels rise:

Urinary & Renal Signs

• Increased thirst (polydipsia)

• Increased urination (polyuria)

• Blood in urine (hematuria) from bladder or kidney irritation

• Formation of calcium oxalate bladder or kidney stones (uroliths)

• Possible urinary tract infections due to stones

Gastrointestinal Signs

• Reduced appetite (anorexia)

• Nausea and drooling

• Vomiting (sometimes chronic, sometimes intermittent)

• Constipation

• Abdominal discomfort

Musculoskeletal & Neurological Signs

• Muscle weakness or reluctance to jump/climb

• Muscle tremors, twitching, or stiffness

• Ataxia (wobbly gait)

• Seizures (in severe cases)

• Generalized lethargy or depression

Behavioral & General Signs

• Irritability or personality changes

• Decreased grooming behavior

• Weight loss and poor body condition over time

Cardiovascular Signs (with severe or prolonged hypercalcemia)

• High blood pressure (hypertension)

• Irregular heartbeat (arrhythmias)

• Collapse in extreme cases

⚠️ Because these symptoms overlap with kidney disease, hyperthyroidism, cancer, and other feline conditions, blood tests and urinalysis are required for diagnosis. Hypercalcemia should always be evaluated by a veterinarian to determine the underlying cause.

Diagnosing Hypercalcemia in Cats

Veterinarians diagnose hypercalcemia through a combination of physical examination, blood tests, and diagnostic imaging. The following steps are typically involved:

1. Blood Tests – A serum biochemistry panel measures total and ionized calcium levels, as well as kidney function and phosphorus levels.
2. Parathyroid Hormone (PTH) Test – Determines if hyperparathyroidism is the cause.
3. Vitamin D Testing – Identifies vitamin D toxicity.
4. Urinalysis – Checks for kidney function abnormalities or urinary stones.
5. Imaging (X-rays, Ultrasound) – Detects tumors, kidney disease, or bladder stones.
6. Bone Marrow Aspirate or Biopsy – In cases where lymphoma or other cancers are suspected.

Treatment Options for Hypercalcemia in Cats

Treatment depends on the severity of hypercalcemia and its underlying cause. The primary goal is to reduce calcium levels while addressing the root issue.

1. Fluid Therapy

Intravenous (IV) fluid therapy is often the first line of treatment. Increasing fluid intake helps flush excess calcium from the bloodstream through the kidneys.

2. Dietary Management

A low-calcium, phosphorus-controlled diet may help manage chronic hypercalcemia, particularly in cats with idiopathic hypercalcemia or CKD.

3. Medications

Depending on the cause, different medications may be used:

• Bisphosphonates (e.g., alendronate) help reduce bone resorption and lower calcium levels.
• Steroids (e.g., prednisone) may be prescribed for inflammatory or immune-mediated causes.
• Diuretics (e.g., furosemide) help increase calcium excretion through urine.
• Calcitonin can be used in severe cases to lower calcium levels temporarily.

4. Treating Underlying Conditions

• Surgical Removal of Parathyroid Tumors – In cases of hyperparathyroidism, surgery may resolve hypercalcemia.
• Cancer Treatment – Chemotherapy, radiation, or surgical removal of tumors can help control calcium levels.
• Infection Management – If granulomatous disease is the cause, antifungal or antibiotic treatment may be necessary.

“Hypercalcemia in dogs and cats. This usually indicates an underlying disease process causing the dysregulation of calcium homeostasis; clinical signs may or may not be evident.” – Kathleen Ham, DVM, MS (Merck Veterinary Manual)

Prognosis and Long-Term Management

The prognosis for hypercalcemia depends on the underlying cause and how quickly treatment is initiated. Cats with idiopathic hypercalcemia can often be managed with dietary changes and medications. However, conditions like lymphoma or advanced kidney disease may have a more guarded prognosis.

Regular veterinary check-ups, blood work, and monitoring calcium levels are essential for long-term management. In some cases, lifelong treatment is required to prevent complications.

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Preventing Hypercalcemia in Cats

While not all causes of hypercalcemia are preventable, as a cat owner, you can take proactive steps to minimize risks:

• Avoid excessive vitamin D supplementation unless prescribed by a vet.
• Keep rodenticides and toxic substances out of reach.
• Provide a balanced diet tailored to your cat’s specific health needs.
• Schedule regular veterinary check-ups to detect early signs of illness.

Hypercalcemia in cats is a serious condition that requires prompt diagnosis and treatment. Understanding the potential causes, recognizing symptoms early, and working closely with a veterinarian can improve a cat’s quality of life. With appropriate medical care and long-term management, many cats with hypercalcemia can lead comfortable lives.

About Petworks

In 2021, Dr. Marty Goldstein DVM joined the pet care platform Petworks as an advisor in its Animal Nutrition care division. Dr Marty Nature’s Blend is on a mission to help your pets live their healthiest lives possible. Dr. Marty’s pet nutrition expertise and guidance has helped Petworks evolve and become the preeminent animal and pet nutrition consultation service for pet parents in North America.

In 2022, Blue Buffalo Founder Bill Bishop Jr. joined Petworks as Senior Advisor in our Animal Nutrition Care Division. Bill brings his extensive expertise in pet food innovation and business leadership. His guidance helps Petworks enhance our pet nutrition service offerings, helping to ensure that pet parents throughout the world receive trusted, science-backed nutritional support for their dogs, cats, and animals.