Radioactive Iodine

The Feline Centre is one of only 10 clinics in the UK that is able to treat hyperthyroid cats with radioactive iodine.

Why are we different?

  • We have over 15 years of experience of providing this treatment and are passionate about treating our hyperthyroid patients
  • We can flexibly adjust the dose of radioiodine exactly to your cat’s own requirements; we use variable dosing from standard through to very high dose therapy (for thyroid carcinoma)
  • We have pioneered the use of high dose therapy for cats with thyroid carcinoma in the UK
  • Our Feline Centre is run by two RCVS Feline Medicine Specialists, who work closely with our large team of Specialists including imaging and cardiology
  • This allows us to assess your cat holistically, to provide the very best recommendations for your cat and its thyroid disease, taking into account that hyperthyroid cats are often older cats with concurrent diseases
  • We have a 'Cat Friendly' approach to working with cats (International Cat Care practice standard) and are a gold standard Cat Friendly Clinic
  • We have cattery style accommodation in our radioiodine ward with webcams, radios and even a television in the ward area to make your cat’s stay as comfortable as possible
  • We can perform scintigraphy. 

Please note there is currently a waiting list, we advise you read the information for vets documents for more details. Please contact reception on 0117 394 0513 to discuss referral and waiting times or submit your request online.


radioactive iodine treatment

Welcome to the Hyperthyroid Treatment Service.

We hope you find the questions below useful. There is also a list of more general questions in our General Info for Owners pages.

 Register for our Newsletter

Client Testimonials


Our aim is provide the very best care for your cat at all times and to ensure that radioactive iodine is the most suitable treatment for your cat; we do this by performing a thorough geriatric health check before treatment.


My cat has been diagnosed with hyperthyroidism, what does this mean?

Hyperthyroidism is the most common hormonal disease seen in geriatric cats. The disease is most commonly caused by a tumour in the thyroid gland(s). In 97-99% of cases the tumour is benign (an adenoma or hyperplasia) and rarely is caused by a malignant tumour (carcinoma). The signs seen in hyperthyroid cats are due to high levels of thyroid hormone released by the tumour. Common signs include weight loss, excessive hunger and thirst, vomiting, diarrhoea, agitation and vocalisation. Rarely cats have a form of the disease called ‘apathetic hyperthyroidism’ where they may be lethargic and inappetant, as opposed to showing the more typical signs. In most cats an enlarged thyroid gland(s) can be felt within the neck, however between 5 to 20% of cats may also have ectopic tissue within the chest.


How is hyperthyroidism treated?

There are four ways that hyperthyroidism can be managed, each with associated pros and cons:

Treatment Pros Cons
No requirement for

Most cats can be stabilised
within 2-4 weeks

Dose can be titrated to effect


No requirement for

Long term requirement for daily or twice daily pill administration or application of transdermal cream

Regular blood tests required for monitoring for complications

Possible side effects include skin irritation and lesions, liver damage, development of abnormalities in white blood cells, red blood cells or platelets (clotting cells)

Does not cure the tumour, only blocks the effect of excess secreted hormone, so the tumour will continue to grow

Increasing doses of the drug may be required with long term treatment 

Dietary therapy Iodine restricted diet Reversible

No requirement for hospitalisation

Not known to be associated with adverse effects and appears to be well tolerated

No requirement for anaesthesia

Long term requirement for the cat to eat the diet only

May be more difficult to follow in a multi-cat household, if the cat hunts and eats prey or requires medication containing iodine

The cat may only temporarily like the diet

Does not cure the tumour, only blocks the effect of excess secreted hormone, so the tumour will continue to grow

Efficacy in long-term hyperthyroidism is unknown

May not be suitable if the cat requires other specific dietary management of other disease e.g. diabetes

Surgery Reduced hospitalisation period required

Technique usually available in first opinion practice

Curative if all hyperactive tissue is accessible to surgeon (i.e. if there is no ectopic tissue within the chest)

Rapidly effective if all hyperactive tissue can be removed

Period of stabilisation ideally required pre-surgery

Anaesthetic required

Risk of parathyroid gland damage if both glands removed and development of low calcium levels, which may require short-longer term medication

Rarely there can be damage to nerves in the neck leading to Horner’s syndrome +/-laryngeal dysfunction

Only suitable if all of the tissue is within the neck region (up to 20% of cats have additional tissue that is inaccessible)

Disease involves both thyroid glands in 75% cats, hence if unilateral surgery initially performed (i.e. 1 gland is removed), cat may develop hyperthyroidism again at a later date (months-years) and require a second surgery

Irreversible treatment-may unmask kidney disease if previously unstable, period of stabilisation with medicine pre-operatively can be predictive of this; some cats may need thyroid supplementation, if levels drop low post surgery, to support renal function

Rarely curative for thyroid carcinoma due to infiltration of local tissue by tumour

Radioactive iodine No anaesthetic required-treatment given as a single injection under the skin with light sedation

Treats all hyperactive tissue regardless of location

High success rate (95%+)

Very few side-effects

No risk of damage to parathyroid glands

Suitable for carcinoma treatment (requires 10x higher dose)

Can be repeated if recurrence at later date or partial drop in hormone level

Limited availability-around nine centres in the UK

Requires period of hospitalisation (10 days for standard treatment, 14 days for intermediate dose treatment and seven weeks for carcinoma treated cats at Langford)

Effective usually within 2-6 weeks, in some cats full effect takes up to six months

A small proportion of cats require a second treatment

Irreversible treatment-may unmask kidney disease if previously unstable, some cats may need thyroid supplementation, if levels drop low post radioiodine, to support renal function


How do I get my cat treated with radioactive Iodine?

one of our patients

You need to initially discuss this with your own local vet, who will then be able to refer you to the Feline Centre; as we are a referral hospital we cannot accept requests directly from owners.  Initially cats come for an assessment appointment (usually over two days), to determine if they are suitable to receive radioactive iodine.



How much will it cost?

one of our patients

The assessment, treatment and post-treatment evaluation costs £2,500 including VAT for routine hyperthyroid patients (with benign disease). This includes hospitalisation for up to four weeks following treatment.

The package cost for thyroid carcinoma (malignant form) treatment is £3,000-£3,600 including VAT.

Please note: clients who booked treatment prior to 1 August 2018 will pay the lower prices from the previous financial year.



Where will my cat stay?

one of our patients

We strive to provide a pleasant, comfortable and stress-free experience for your cat; our treatment wards have cattery style accommodation with plenty of space for the cats to stretch out and we provide lots of comfortable bedding, hidey-holes, toys and scratching posts to occupy the cats during their stay, we even have cat TV!



Why does my cat have to be assessed if I know I want them to be treated?

one of our patients

As most of the cats with hyperthyroidism are senior or geriatric, it is very common for them to have concurrent disease, which may not be visible from the outside.  For this reason your cat will be carefully assessed to see if there are any other major problems, which could change your or our minds as to whether your cat is suitable to receive radioactive iodine. 

Secondly once a cat receives radioactive iodine, he/she will be hospitalised in a special ward.  If problems arise the cat cannot be brought back to the main hospital, due to health and safety rules and we can only perform nursing treatment.  For this reason we do a ‘geriatric MOT’ to minimise the risks as much as possible.


What does the assessment appointment involve?

one of our patients

This is a complete check-up. We like to review blood tests (if not performed in the last few weeks by your own vet), analyse urine and measure your cat’s blood pressure.  We then perform imaging of the chest, abdomen and heart.  We are particularly looking for complications of hyperthyroidism (e.g. high blood pressure and heart disease), as well as concurrent diseases.  Secondly if possible we try to assess your cat’s kidney function whilst the hyperthyroidism is well stabilised; 30-50% of hyperthyroid cats also have concurrent kidney disease, which may be hidden when the hyperthyroidism is uncontrolled.  It is not unusual to unmask kidney disease by treating the hyperthyroidism but fortunately in most cases this is mild kidney disease that can be treated medically.  It is however important to treat the hyperthyroidism appropriately in this situation, to avoid further damage to the kidney.

We usually perform the radioiodine assessment 4-6 weeks in advance of a provisional treatment date, as things can change quite quickly in older cats and to allow time for certain problems to be addressed for example urinary tract infections.



Can my own vet do this assessment?

We prefer to do the assessment at the Feline Centre if possible, to develop a good understanding of your cat.  We are however happy to work with your vet for some of the assessment to be done locally, but do ask for a specialist imager to perform a heart and abdominal scan, ideally at the Feline Centre.  Please bear in mind that the assessment we perform is part of a package price for assessment, treatment and follow-up.  The price would obviously be adjusted if some of the tests are carried out locally by your own vet, and we would need to liaise closely with your vet over the tests required.


I live a long distance from the Feline Centre, can I avoid several trips?

In exceptional circumstances, we maybe able to arrange for an assessment appointment close to a treatment slot, however this will involve boarding your cat for 7-9 days after the assessment, whilst we await the iodine order (which comes from overseas).  Please ask your vet to discuss this with the Feline Centre staff.


What happens when my cat comes in for treatment?

Your cat will be admitted 24-48 hours in advance of the planned treatment date, to allow him or her time to settle in and get over the car journey.  We obtain a baseline thyroid hormone (T4) measurement and recheck blood pressure; all thyroid medication will have been stopped one week in advance as we need to establish exactly how high your cat’s T4 is off of tablets (we will advise regarding discontinuation of dietary therapy and transdermal medication on an individual basis). 

The radioactive iodine injection is usually given on a Thursday or Friday, under a light sedation.  Following this your cat is hospitalised in a special radioiodine ward, and looked after by the medicine team nurses, with visits from the primary vet in charge of your cat’s care.  The ward is similar to a cattery, with large pens, containing shelves at different levels.  We provide various beds (including a cosy cat cabin), scratching posts, a radio and cat nip toys.  We even have a cat TV in one ward, with a special cat DVD to entertain the patients!  We can feed whatever diet your cat prefers, or requires if he/she is receiving a special prescription diet.  We have webcams to be able to check your cat from within the main hospital too (unfortunately this is not accessible externally). 

If you wish to provide something from home that you feel will help your cat settle in, we are happy to put that in the pen too, however please be prepared that if there is any contamination we may not be able to allow this to leave the hospital afterwards.  Equally if you have a particularly special food that you like to feed your cat, please bring that along too.


Can I visit my cat in the radioiodine ward?

Unfortunately this is not possible, due to health and safety regulations.  We are however happy to provide updates on a regular basis, we can text messages to you which many clients like.  In our experience it is extremely rare for cats not to settle in the radioiodine ward, once the injection has been given the stay is really no different to a routine cattery stay; it sometimes seems that this period is harder for owners waiting at home than the patients!


When can my cat come home?

The hospitalisation period for cats treated with standard doses currently is 10 days, and for cats treated with intermediate doses 14 days (we determine the dose required based on your cats thyroid hormone level, severity of disease and thyroid tumour size); it is longer for cats being treated for thyroid carcinoma (seven weeks in total). For the standard and intermediate treatment, cats can leave our hospital after 10 and 14 days respectively, provided the following restrictions can be observed (exact timings will be discussed by your clinician)

- maintain your cat indoors for approximately two extra weeks

- avoid contact with young children or pregnant ladies for approximately two extra weeks

- avoid prolonged periods of direct contact with your cat for approximately two extra weeks (e.g. keep out of occupied bedrooms at night)

- handle waste with rubber gloves and double bag any waste before disposing of in general rubbish for approximately three extra weeks.


Why is the hospitalisation time shorter in other hospitals?

Our restrictions are set by a Radiation Protection Officer, according to interpretation of Environmental Agency and local radiation regulations.  Unfortunately there is no accepted UK consensus as to when it is safe for a cat to return home and different hospitals may use different doses of radioiodine for treatment.


You can download a full version of the owner FAQs here.


Owner Testimonials

Read the case studies below for client stories and testimonials for our Radioactive Iodine Service, or alternatively head to the link below for further client testimonials for our Feline Centre.

Feline Centre Testimonials


Mary's Story

Mary, an 11 year old Domestic Short Hair cat travelled from London to the Feline Centre in 2011 for her radioactive iodine treatment. She had been diagnosed with hyperthyroidism 18months earlier however had not been able to tolerate medication well, meaning that she could not be fully stabilised with tablets.

Mary had a successful rapid response to radioactive iodine and sailed through her four week stay at the Feline Centre, without any problems. Mary's owner talks about the experience at Langford…


Mary's owner's testimonial

'I'm immensely grateful to the Langford Veterinary Services and Angie Hibbert for their wonderful care of my cat Mary when she needed treatment for hyperthyroidism. Having driven Mary down from London, I was immediately struck by how quickly Mary relaxed and settled in at the clinic; she wasn't at all agitated and nervous being in a new environment.

The veterinary students were very conscientious when taking Mary's history, even sitting with me and Mary on the floor in order to put Mary at ease.

A thorough set of tests was taken to ensure that Mary was a good candidate for the radioactive iodine treatment, and the clinic was able to board Mary between her tests and the treatment, avoiding unnecessary and stressful trips up and down the M4.

I was anxious about how Mary would react to being in the radioiodine ward while after her injection - probably more anxious than Mary. But the staff at the Langford were thoughtful and considerate, calling every day with updates on Mary's condition, giving me confidence that she was both well and being well cared for.

They were happy for Mary to have her own bedding, toys and food while she was in the ward and I felt sure Mary was getting the best possible care.

At the end of the treatment, I was reunited with a healthy, happy cat, and was given full instructions for Mary's post-treatment home care. Eight months on, and Mary is a gorgeous, calm and affectionate cat - it's as if she's been given a new lease of life. Thank you, Langford!'


Tudor's Story


Tudor, a 9 year old male Domestic shorthair also came to the Feline Centre in 2011 for radioactive iodine. Tudor had been diagnosed with hyperthyroidism only six weeks earlier and shortly after starting tablets to control the condition developed a severe reaction to the drug.

Tudor became intensely itchy and began to scratch his face causing terrible wounds over his head and neck. It was clear that Tudor was not going to be able to continue medical treatment in the long term and after his assessment we were happy that he would be a good candidate to receive radioactive iodine.

In the interim he was treated with anti-histamines, to control his itchiness and antibiotics, as the skin wounds had become infected.

Tudor also responded very quickly to radioactive iodine treatment, with resolution of his hyperthyroidism on returning to the ward, healing of all of his skin lesions and weight gain.

He was a much happier and relaxed cat, and is back to looking his best again as this photo shows!