What causes hyperparathyroidism in dogs and cats?

Hyperparathyroidism is most often caused by an abnormality or tumour of the parathyroid gland, leading to elevated blood calcium. The exact cause requires confirmation through blood tests and imaging — your vet can guide you through the evaluation.

What tests are needed to confirm the diagnosis?

Common tests include a complete blood count, biochemistry panel, electrolyte measurement, and parathyroid hormone (PTH) testing. Ultrasound or advanced imaging may also be recommended as needed.

What are the treatment options, and is long-term follow-up needed?

Treatment options may include medication or surgery depending on the cause. Ongoing monitoring of blood electrolytes and kidney function is required after treatment, so regular follow-up visits are important.

My pet is drinking more water but seems otherwise fine — what should I do?

If your pet is drinking more water but still seems alert and is eating reasonably well, it is a good idea to log their water intake and urination and arrange a clinic visit within 24–72 hours to catch any issues early.

How much do the tests and treatment usually cost?

Costs vary by clinic and region — ask your vet for an estimate before proceeding.

Disease Guide

Hyperparathyroidism in Dogs & Cats: Symptoms, Diagnosis & Treatment [2025]

Hyperparathyroidism causes elevated blood calcium levels, most commonly due to a parathyroid gland tumour in cats. Signs include increased thirst, frequent urination, and reduced appetite. Surgical removal of the affected gland is the preferred treatment, with close monitoring of calcium levels after surgery.

Take 1 minute to check the symptoms first

Last updated: 2026/01/05

Pethealthmap Editorial Team

Sources: ACVIM, WSAVA, National Taiwan University Veterinary Hospital

When to See a Vet

Seek immediate veterinary care (emergency)

•Persistent seizures or whole-body convulsions lasting several minutes or longer
•Sudden loss of consciousness and cannot be awakened or is unresponsive
•Persistent vomiting with inability to stand or coma

Schedule a clinic visit as soon as possible (within 24-72 hours)

•Persistent vomiting while still conscious and active
•Markedly increased water intake and frequent urination
•Decreased appetite or obvious short-term weight loss

01What signs suggest something is wrong?

Hyperparathyroidism commonly affects energy, digestion, and the urinary system. Symptoms may appear subtle at first but tend to worsen gradually.

Lethargy, slow responses, or unusual drowsiness
Noticeable weakness, decreased activity, or reluctance to move
Reduced appetite or becoming selective about food
Repeated vomiting, nausea, or digestive discomfort
Increased water intake, frequent urination, or changes in urine output

Seek emergency care immediately if you notice the following symptoms:

⚠️ Seizures or full-body convulsions lasting more than a few minutes
⚠️ Sudden loss of consciousness with no response to stimulation
⚠️ Persistent vomiting combined with inability to stand or collapse

02How can you assess the situation at home? Key observations and when to go to the emergency clinic

Keeping a record of symptoms at home helps the vet assess the situation quickly and arrange any necessary tests.

Note when symptoms first appeared and how they have changed over time
Track daily water intake and how often your pet drinks
Record the number of vomiting episodes, what was vomited, and when
Observe and note urination frequency and any changes in urine volume
Monitor appetite, food intake, and any recent weight changes
Seek veterinary care promptly if symptoms worsen or change suddenly

03How will the vet diagnose this condition? Common diagnostic tests

The vet will start with a physical examination, then use blood tests and imaging to identify the underlying cause and any complications.

Physical examination

palpation, cardiovascular, pulmonary, and neurological assessment

Blood tests and biochemistry panel to evaluate electrolytes and organ function

Abdominal or thoracic ultrasound to assess organ structure

X-rays or advanced imaging (CT/MRI) as needed to identify lesions

Referral to a veterinarian or specialist hospital with endocrinology experience is recommended for ongoing management

04How is it treated and managed after diagnosis? Medication, diet, and care guide

Treatment depends on the root cause and may include medication, surgery, or supportive care, along with long-term blood monitoring.

Medical treatment and supportive care tailored to the underlying cause
Surgical evaluation and intervention if a suspicious mass or lesion is found
Dietary adjustments and fluid management as important supportive measures
Regular follow-up visits after discharge to monitor blood electrolytes and organ function
Long-term management with an endocrinology specialist or a vet familiar with the case

05What should you prepare before the appointment? Key information to help the vet

Write down when symptoms started, how often they occur, and any changes over time

Bring any recent blood test results or imaging reports if available

Prepare a log of your pet's water intake and urination over the past week

List all current medications and supplements your pet is taking

If you have video of vomiting episodes or seizures, share it with the vet

This content is for reference only and cannot replace a professional veterinary diagnosis. If your pet shows signs of illness, please seek veterinary care promptly.