DATA-BACKED GUIDE · UPDATED JULY 2026
Radioactive iodine for hyperthyroid cats: what it costs in the UK
Radioactive iodine, often written as I-131, is widely seen as the gold-standard treatment for an overactive thyroid in cats because it usually cures the problem in a single treatment. The upfront bill makes owners wince, but over a cat's remaining years it can work out cheaper than daily tablets. The real prices below show what specialist centres are charging.
The quick version
- Radioactive iodine cures most hyperthyroid cats with one treatment and no ongoing tablets.
- It is offered only at licensed referral centres, so availability and travel affect the cost.
- The price includes a hospital stay of one to two weeks for radiation safety.
- A lifetime insurance policy taken out before diagnosis often covers most of the bill.
What people actually paid
Why the price varies so much
Because only a handful of licensed centres in the UK can handle radioactive material, prices differ by region and waiting list rather than by high-street competition. The quoted fee covers a stay of one to two weeks while the radiation drops to safe levels, so nursing time is baked in. Whether your cat needs extra scans or has other conditions such as kidney disease also shifts the total. Set against daily medication plus lifelong blood tests, the one-off nature of I-131 is what makes it competitive, especially as ongoing vet costs have risen sharply, up around 63% between 2016 and 2023.
How to pay less
- Ask your vet for referral options at more than one centre, as prices and waiting times differ.
- Check your lifetime pet insurance covers referral treatment before booking anything.
- Compare the one-off cost against several years of tablets and repeat blood tests.
- Factor in travel and the hospital stay, but remember there are no follow-up medication bills.
Common questions
Is radioactive iodine a permanent cure?
For the large majority of cats, one treatment permanently resolves the overactive thyroid with no further medication needed. A small number need a second treatment, and your specialist will monitor thyroid levels afterwards to confirm success.
Why is my cat kept in hospital for so long?
Your cat is mildly radioactive for a short period after treatment, so licensing rules require a stay of roughly one to two weeks until levels are safe. You usually cannot visit during this time, but the centre keeps you updated.
Is radioactive iodine cheaper than tablets long term?
It can be. Daily medication plus the regular blood tests needed to monitor it never stops, so over several years the running total often overtakes the single upfront cost of radioactive iodine, particularly for a younger senior cat.