For Veterinarians

Please forward the medical history and any associated laboratory values so that we can provide you with an individualized treatment plan.

Each patient will be assessed on an individual basis.

No treatment date will be provided until our staff has reviewed your patients file. All cat files are reviewed at no cost to the referring clinic or the owner.

Please note there is no referral form required.

If your client would like to pursue iodine treatment we will provide a treatment plan which will include dates for tests, when to come off medication (if applicable) and when the treatment date is scheduled.

HyperT masks true renal function. When possible, we would like to obtain a better understanding of how the kidneys are functioning. This can be achieved by performing a trial with any of these products: oral or transdermal tapazole or y/d trial. The length of time required for a trial is determined by T4, length of time on medication and current kidney enzymes.

Factors that can affect a trial not being performed are:

  • Allergic RX.

  • Owner compliance.

  • Inability to provide pills for various reasons.

  • Multi-cat household.

Mandatory Tests

  1. Urinalysis

    1. We will need a UA +/- UCS (if USG is less than 1.035 and/or if there is active sediment on the UA).

    2. We are finding that many HyperT cats have concurrent undetected UTIs.

    3. Culture and Sensitivity is mandatory for all USG 1.035 or below – no exceptions.

  2. If a heart murmur/gallop rhythm is present a 3 view chest x-ray is required to assess heart size.

    1. (A 2 view chest x-ray is the minimum requirement).

    2. If there is not heart murmur this is not required. Please provide your interpretation of the x-rays.

  3. There are some exceptions however most cats will be off medication 14-18 days prior to treatment.

    1. Total T4 must be performed at a reference laboratory – no exceptions -~ 5 days before the treatment date. This is the value used to calculate the iodine dose.

  4. Rabies vaccination must be up to date to board at our facility. If it is overdue, please administer at least 7 days prior to their Radioactive Iodine Treatment appointment.

Additional Tests

Additional tests may be recommended based on above results.

  1. If there is a heart murmur, heart enlargement, or concern for underlying heart disease then an echocardiogram would be beneficial to assess underlying heart function.

  2. ProBNP

  3. Abdominal US on a case by case basis

We stand behind our services so if a top up dose is required it will be provided at no additional cost to the client. The guarantee is based on the owner having two follow up T4 checks from a reference laboratory:

  • First check at ~14 weeks post treatment.

  • Second check at ~10-12 months post treatment.

These follow up checks are at the owners’ expense.

Ideally, at one of these time points we would like a renal panel completed however this is not mandatory.

Length of Stay

Based on T4 value and associated dose required - typically 4 – 8 days.

There are some cases where the stay may be longer however we would know this prior to treatment.


Most cats respond to a single dose of I-131, however, about 5% of cats require re-treatment with a higher dose of I-131 to achieve euthyroid values. There is also about 1-2% of cats where radioactive iodine is not effective at all. In these kitties, the thyroid tissue stops absorbing Iodine and will not destroy the overactive thyroid cells. Most of the overactive thyroid tissue will be destroyed within 3 months of I-131, although some cats do have an additional effect seen up to 6 – 9 months after treatment.

We have seen that cats who have excessive drinking/urination or that have concurrent severe intestinal disease are more likely to require a second I-131 treatment. Top up dose/s are provided at no cost to the owner.

*Some exceptions may apply.


It is very important that your patient is feeling well when coming in for I-131 therapy. It is imperative that you let us know if your patient is feeling unwell – decreased appetite, V+/D+ etc – before they come for their I-131 appointment.

Flushable litter and reducing close exposure time must be implemented at home for 2 weeks following treatment. We have more information about home care on our website. We will also explain this information to your client.

Contact Info

Thames Valley Vet Services

268 Grosvenor St.

London, ON N6A 4V2

Phone: (519) 646-6100 x 64679#

🖷 Fax: (519) 646-6205