Hyperthyroidism is the most common endocrine disorder in cats, primarily affecting older cats.

It occurs when the thyroid glands become overactive, leading to an excessive production of thyroid hormones. If left untreated, hyperthyroidism can have detrimental effects on a cat’s overall health.

Signs that your cat might have an overactive thyroid include drinking and eating more, and weight loss. You also may notice your cat becoming very vocal and needy.

However, with timely diagnosis and appropriate treatment, cats with hyperthyroidism can lead long, happy and comfortable lives.

We offer senior pet wellness checks to make sure we’re doing everything we can to help your cat remain healthy as they enter their golden years.


We can confirm a diagnosis of hyperthyroidism with a blood test.

Occasionally in the early stages of the condition, this blood test may be inconclusive – if this is the case, we repeat the test four to six weeks later.

Treating with medication

Anti-thyroid medications are commonly prescribed for cats with hyperthyroidism.

The most commonly used medication is methimazole, which works by reducing the production of thyroid hormones. It is available in tablet form and is usually given orally.

Regular monitoring of thyroid hormone levels and kidney function is necessary to ensure the cat is receiving the correct dosage.

Members of our Practice Plan receive unlimited consultations throughout the year – perfect for helping us keep an eye on hormone levels! Join online today.

Radioactive iodine therapy

Also known as I-131 treatment, this is considered the gold standard for treating hyperthyroidism in cats.

It involves administering a radioactive form of iodine, which specifically targets and destroys the abnormal thyroid tissue while leaving healthy tissue unharmed.

This treatment is highly effective, with a success rate of over 95%. However, it requires specialised facilities and may involve a brief hospital stay for the cat due to radiation safety precautions.

Unfortunately this treatment is soon to become unavailable due to supply issues with radioactive iodine.

Surgical thyroidectomy

Surgical removal of the thyroid gland, known as thyroidectomy, is another treatment option.

This procedure is typically recommended for cats that are not suitable candidates for radioactive iodine therapy or medication.

Thyroidectomy can be curative, but it requires general anaesthesia and carries the risk of complications such as damage to the parathyroid glands.

Close monitoring of calcium levels after surgery is often required.

Prescription diets

Prescription diets formulated for cats with hyperthyroidism can also play a role in managing the condition.

These diets are low in iodine, which helps reduce the production of thyroid hormones.

However, they are not considered a standalone treatment and are often used in combination with other therapeutic approaches. Also, the diet needs to be the only food the cat eats during the treatment, so it isn’t suitable for an outdoor cat.

It is essential to follow your vet’s guidance regarding the appropriate diet and feeding recommendations, so please speak to us to work out the best solution for your pet.

If your cat is showing signs of hyperthyroidism, book an appointment to see your vet.

Supportive care

In addition to the primary treatments mentioned above, supportive care is crucial for cats with hyperthyroidism.

This includes regular monitoring of thyroid hormone levels, kidney function and other blood parameters.

It is important to address any concurrent medical conditions and provide appropriate medication, hydration and a balanced diet.

Senior cats may also benefit from additional support, such as joint supplements or pain management, to improve their overall well-being.

We’re here to help

The choice of treatment depends on various factors, including the cat’s age, overall health, and individual circumstances.

It is important to work closely with your vet team to determine the most suitable treatment approach for each cat.

With proper treatment and care, cats with hyperthyroidism can enjoy a good quality of life for years to come.