A closer look at radioactive iodine treatment for cats at CSS

Hyperthyroidism in cats occurs when a benign tumour in the thyroid gland overproduces thyroid hormones, accelerating metabolism and causing significant health issues. Radioactive iodine therapy (I-131) is a safe, curative, effective and minimally invasive treatment.

“The thyroid is really the only gland in the body that uses iodine,” explains Dr Rachel Korman. “So the radioactive iodine is absorbed directly into the thyroid and acts very locally to destroy the overactive parts without damaging anything else.”

Unlike medication, which requires lifelong administration and frequent monitoring, or surgery, which carries anesthesia risks and potential complications, radioactive iodine therapy provides a definitive solution. “If I had to choose for my own cat,” Dr Korman says, “there’s no way I’d want to be giving tablets twice a day for the rest of their life. Not only is it stressful for both the cat and the owner, but over time, the medication dosing changes as the thyroid tumours grow, so there needs to be re-evaluation and blood tests.”

Hyperthyroid cats are often older and may have manageable underlying conditions such as mild heart disease or kidney concerns. At CSS, we’re equipped with on-site specialists to ensure these cats are stabilised and carefully monitored before, during and after treatment.

Even if your cat has other health concerns, it’s always worth discussing I-131 therapy with us. With the right approach and expert oversight, many cats with co-existing conditions can still receive safe and effective treatment.

Before treatment, each cat undergoes a thorough medical review and physical examination to assess overall health and rule out contraindications, such as advanced heart or kidney disease. We typically perform blood tests to determine thyroid hormone levels and ensure there are no other underlying conditions that could affect treatment.

Every cat’s condition is unique, so the iodine dose is tailored specifically to their thyroid hormone levels and goitre size. “We put all of that together to determine the iodine dosage that’s specific to that individual,” explains Dr Rachel Korman.

On treatment day, the cat receives a single capsule of radioactive iodine, administered the same way as a worming pill. The iodine is quickly absorbed by the thyroid gland, where it begins selectively destroying the overactive tissue while sparing healthy cells.

Cats stay in our purpose-built, spacious isolation units for around a week, and we closely monitor them to ensure their health and comfort.

Once the radioactivity levels have safely decreased, patients can return home. Owners must follow temporary precautions, like keeping their cat indoors and limiting close contact for a couple of weeks. If this isn’t feasible, our medical boarding services are available.

“Cats are so attuned to their space and routine,” says Dr Rachel Korman. “Even just hearing dogs can be stressful, which is why a cat-only setting makes a real impact on their recovery.”

Every cat responds differently to hospitalisation, which is why the team at CSS adjusts care based on individual needs. “The nursing team puts so much effort into understanding what each cat likes—whether it’s a specific type of food, bedding, or just adjusting their space to make them feel more secure,” says Dr Korman.

Many assume radioactive iodine treatment is expensive, but while there is an upfront cost, it proves to be far more cost-effective in the long run. “If you calculate the cost of daily medication, blood tests, and increasing doses over the years, radioactive iodine actually ends up being the cheapest option by miles,” says Dr Korman.

Radioactive iodine is a well-regulated, low-risk therapy. Some people mistakenly believe it poses significant risks. “This is a treatment humans receive, too,” says Dr Korman. “Cats just need a short isolation period to ensure safety, but after that, the risk is minimal.”

If your precious cat has been diagnosed with hyperthyroidism, radioactive iodine therapy offers a curative solution. Our specialist-designed facility ensures each patient receives a thorough assessment, with on-site access to cardiology and other experts for a seamless treatment process.

At CSS, our cat-exclusive clinic is designed for comfort and minimal stress, giving every cat the best chance at a smooth recovery.

To learn more about our radioactive iodine services, contact our team today. Vets can refer patients for treatment here.

If you are concerned about your cat, please reach out to our friendly team. Call us on 1300 228 377 or fill out the contact form below. In an emergency, please contact your local vet.

For vets – to refer a patient or book a telehealth consultation, please call us on 1300 228 377, book through the portal or fill in the form.