Veterinary Guide to Hypercalcemia in Dogs (High Blood Calcium) 2025 🐶

By Dr. Duncan Houston BVSc

🔍 Introduction

Hypercalcemia means elevated calcium in the blood. While mild bumps may be transient, persistent or high calcium is often a red flag for serious conditions like cancer, gland disorders or renal/endocrine issues. This 2025 guide explains causes, clinical signs, diagnostics, emergency management, treatments, and long‑term care. 🩺

💡 What Is Hypercalcemia?

• Lab definition: total calcium >10.7 mg/dL (2.6 mmol/L) or elevated ionized calcium.
• Mild, asymptomatic elevations can exist, but levels >15–18 mg/dL require urgent attention.

⚠️ Common Causes

• Hypercalcemia of malignancy: accounts for ~60% of canine cases, especially lymphoma and anal sac tumors.
• Primary hyperparathyroidism: parathyroid adenoma/hyperplasia secreting excess PTH.
• Addison’s disease: present in up to 30% of cases.
• Chronic kidney disease: can elevate total calcium.
• Vitamin D toxicity: from supplements, plants or rodenticides.
• Granulomatous/inflammatory disease: fungal or immune‑mediated.
• Rare causes: bone tumors, nutritional hyperparathyroidism.

🚨 Clinical Signs

• Lethargy, weakness, loss of appetite, vomiting, constipation.
• Increased thirst and urination; risk of urinary stones and kidney issues.
• Neurological or cardiac signs—arrhythmias, tremors, seizures—especially in severe cases.

🔬 Diagnostic Approach

• Confirm hypercalcemia: repeat total calcium in fasted state, measure ionized calcium.
• Routine work‑up: CBC, biochemistry, urinalysis, PTH and PTHrP levels, electrolytes.
• Imaging: thoracic and abdominal radiographs, ultrasound to detect tumors or stones.
• Endocrine tests: ACTH stimulation for Addison’s, vitamin D assay if toxicity suspected.
• Further diagnostics: cytology/biopsy of masses or lymph nodes.

🏥 Emergency Management

• Intravenous fluids: 0.9% sodium chloride to promote calcium excretion.
• Furosemide: after rehydration, increases renal calcium clearance.
• Glucocorticoids: helpful in hypervitaminosis D or malignancy‑associated hypercalcemia.
• Bisphosphonates or calcitonin: reduce bone resorption in severe cases.
• Dialysis: used in critical nonresponsive cases.

🧠 Addressing the Underlying Cause

• Cancer: surgical removal, chemo/radiation for lymphoma or anal sac adenocarcinoma.
• Parathyroid tumor: parathyroidectomy or ablation depending on case.
• Addison’s disease: standard hormone replacement therapy.
• Vitamin D toxicity: discontinue sources; treat symptoms.
• Granulomatous disease: targeted antifungal or immune‑modulating therapy.

📈 Follow-Up & Prognosis

• Regular monitoring of calcium, kidney function, electrolytes and response to therapy.
• Prognosis depends on cause: good for parathyroid & Addison’s, guarded for malignancy.
• Long-term relapse possible—esp. in cancer cases—hence lifelong follow‑up.

🛡 Prevention & Owner Tips

• Annual wellness exams with calcium checks—even asymptomatic elevations matter.
• Caution with vitamin/mineral supplements—avoid unsupervised use.
• Endocrine disease monitoring if Addisonian or parathyroid conditions are risks.
• Prompt evaluation of symptoms like increased drinking, GI upset or lethargy.

🔧 Tools & Services

• Ask A Vet App: 24/7 guidance on lab results, early signs & when to seek care 📱

✅ Final Thoughts

Hypercalcemia is more than a lab result—it often reflects serious disease. Timely identification, emergency care, and targeted treatment significantly affect outcomes. With ongoing monitoring and tools like Ask AVet, owners can support their pet through timely diagnostics and care into 2025 and beyond. 🐾❤️

Download the Ask A Vet app today for expert support with calcium-related concerns, diagnostics, and treatment paths. 📱💡