A practical approach to canine hypercalcaemia
Canine hypercalcaemia is a relatively common finding in veterinary practice, often detected on routine bloodwork or in dogs presenting with vague clinical signs. This means that vets must always be prepared to interpret calcium results in context and determine whether further investigation is warranted.
While mild cases may be asymptomatic, significant elevations in calcium can cause polyuria and polydipsia (PU/PD), lethargy, vomiting, and muscle weakness. In more severe cases, cardiac arrhythmias, renal damage, and neurological symptoms can develop.
Let’s look at what to do if you suspect hyperCa+ (or spot it in your patient’s blood results), how to test, and when to treat.
First steps: testing for canine hypercalcaemia
Once hypercalcaemia is suspected, the first step is to confirm whether the elevation is genuine. Measuring total calcium is useful as an initial screening tool and is included in most routine panels. However, many things can affect total calcium readings, including age, diet, sample haemolysis, bilirubinaemia, and hyperlipidaemia. That said, total calcium of over 12 mg/dL is highly predictive of true hypercalcaemia.
Measuring ionised calcium provides a more accurate assessment of clinically relevant hypercalcaemia and should be undertaken for any patient with a high total calcium result. If ionised calcium is elevated, further investigation is required to determine the underlying cause. In cases where the elevation is mild, repeating the test after a few weeks can help differentiate between transient and persistent hypercalcaemia.
Common causes of canine hypercalcaemia
Once canine hypercalcaemia is confirmed, identifying the underlying cause is crucial. Some of the most common conditions associated with elevated calcium include:
Neoplasia – Lymphoma and anal sac adenocarcinoma are among the most common malignancies linked to hypercalcaemia, primarily due to the production of parathyroid hormone-related peptide (PTH-rP).
Primary hyperparathyroidism – A benign adenoma of the parathyroid gland can lead to excess secretion of parathyroid hormone (PTH), driving calcium levels up.
Chronic kidney disease (CKD) – Although more commonly associated with secondary hyperparathyroidism, some dogs with CKD may develop hypercalcaemia.
Hypoadrenocorticism (Addison’s disease) – A well-recognised but uncommon cause of hypercalcaemia in dogs.
Vitamin D toxicity – Ingestion of vitamin D supplements, rodenticides, or certain plants can result in dangerously high calcium levels.
Granulomatous disease – Conditions like fungal infections can drive hypercalcaemia through increased production of vitamin D.
Stepwise diagnostic approach: narrowing down the cause
Determining the underlying cause of canine hypercalcaemia requires a logical, stepwise approach:
1. Initial bloodwork
- Urea and creatinine – To assess renal function and rule out kidney-related causes.
- Phosphorus levels – Low phosphorus suggests primary hyperparathyroidism, while high phosphorus points towards renal disease or vitamin D toxicity.
- PTH and PTH-rP testing – Elevated PTH with high calcium confirms primary hyperparathyroidism, while high PTH-rP supports a malignancy diagnosis.
- Vitamin D metabolites – If toxicity is suspected.
2. Imaging
- Thoracic radiographs – Screening for lymphoma or metastatic disease.
- Abdominal ultrasound – Assessing the adrenal glands, kidneys, and GI tract.
- Cervical ultrasound – Identifying a parathyroid adenoma.
3. Additional tests if needed
- ACTH stimulation test – If Addison’s disease is suspected.
- Urinary calcium:creatinine ratio – Helps differentiate primary hyperparathyroidism from renal disease.
Treatment of canine hypercalcaemia
The immediate priority in cases of severe canine hypercalcaemia is stabilisation:
- IV fluid therapy (0.9% NaCl) – Expands volume and promotes calcium excretion.
- Furosemide – Increases renal calcium loss (only once dehydration is corrected).
- Bisphosphonates – Inhibit bone resorption, useful for malignancy-associated hypercalcaemia.
- Steroids – Can be useful but should only be used after diagnostic testing, as they can interfere with lymphoma detection.
For long-term management, treatment depends on the underlying cause. Surgical removal of parathyroid adenomas is the preferred option in cases of primary hyperparathyroidism, while neoplastic causes may require chemotherapy, radiation therapy, or palliative care. Renal disease-related hypercalcaemia is often managed with dietary modifications and phosphate binders, whereas Addison’s disease requires hormone replacement therapy. In cases of vitamin D toxicity, eliminating the source and providing supportive care is crucial. Ongoing monitoring is essential in all cases to prevent recurrence and manage complications effectively.
Take-home messages for veterinary teams
- Canine hypercalcaemia should never be ignored, even if it is an incidental finding.
- Measuring ionised calcium is essential for confirming true hypercalcaemia.
- A structured diagnostic approach ensures efficient case management.
- Early intervention improves patient outcomes, especially in cases of malignancy.
Did you enjoy this summary? For vets looking to enhance their expertise in internal medicine, a Postgraduate Certificate (GPCert/PgC) in Small Animal Medicine provides in-depth training and clinical decision-making skills to tackle cases like hypercalcaemia with confidence.
P.S Don’t forget to log reading this article as CPD – we’d recommend putting it as ‘self directed’ and ‘veterinary reading’. You’ll also need to reflect on what you learned – you might find helpful tips and prompts to help in our article Reflecting on Veterinary CPD. Or, for more free CPD, head over to our Content Hub and browse!
