So your cat’s been diagnosed, they’re on methimazole or carbimazole, and your vet has started talking about next steps. The medication is doing its job for now – but it’s not a cure, and most owners eventually want something more permanent.

Here’s how the treatment options compare.

Daily medication

Most cats that are newly diagnosed with hyperthyroidism are started on daily medication. This is administered either via tablets or transdermally (onto the skin).

It’s worth remembering: long-term medication means twice-daily dosing, blood tests every few months, and the possibility of side effects.

Radioiodine — the ‘gold standard’

There’s a reason radioiodine gets called the gold standard, and it’s not just marketing. A single injection of iodine-131 seeks out the overactive thyroid tissue and destroys it. Healthy tissue is left alone. No general anaesthetic, no surgical wound, and cure rates between 95% and 99%.

The part that’s hard is the stay. UK regulations mean your cat has to remain at the treatment centre while radiation levels drop – that’s anywhere from 4 days to about 2 weeks depending on where you go. You can’t visit. The facilities are purpose-built and the cats are well looked after, but that doesn’t make the wait easy.

Expect to pay somewhere between £3000 and £4000. That usually covers the injection and hospital stay, but blood work and follow-up appointments are often billed separately. Your vet will need to submit a referral, and the centre will want recent bloods, blood pressure, and sometimes a heart scan before they’ll book your cat in.

Surgery

Removing the affected thyroid gland is a straightforward procedure and it can be curative. It tends to work best when only one gland is overactive. The most common complication people is damage to the parathyroid glands – they sit right next to the thyroid and control calcium levels. If both thyroid glands need removing, the risk goes up. And even after a successful single-side surgery, the other gland can become a problem down the line. This surgery also requires a general anaesthetic, which is higher risk in hyperthyroid cats, which are often geriatric and have co-morbidities (other diseases as well as hyperthyroidism).
It’s cheaper than radioiodine, but that lower price tag doesn’t always tell the full story if your cat ends up needing further treatment later.

Where to get radioiodine treatment?

Only a handful of centres in the UK are licensed to offer radioiodine – speak to your vet about which centre is closest or most appropriate for your cat.