I-131 FAQs

What exactly is going to happen to my cat while he or she is at VIS?

On the day of your pet’s arrival, a small injection of I-131 will be given under the skin. The following days your cat will not experience any discomfort secondary to the treatment. The room is well-ventilated with continual background music played for your cat’s enjoyment. There is no physical or psychological side effects to the treatment.

Does it require general anesthesia?

Both the thyroid scan and treatment are normally done under sedation, but not general anesthesia. General anesthesia may be used if the patient is fractious or uncooperative.

Can I visit my cat?

Due to the radiation levels, you are not able to visit your cat while he or she is staying with us.

How long is my cat going to stay at your facility?

The State of Illinois has new regulations regarding the release of “animals that have received I-131 Treatments”: your cat will be ready to go home when his/her radiation level is less than 0.25mR/hr at 1 foot. We estimate it will take approximately 5 nights, but in some rare cases, maybe longer.

I have multiple animals in the house; do I need to be concerned about them?

It is fine for the animals to all share the same water dish, food bowls, and litter box. If several cats share the same litter box, you must use flushable litter and treat all the urine and feces as if they came from the cat treated.

Do I need to worry about the radiation?

All of us are exposed to radiation in our daily lives. The earth, air, and water we drink all contain small amounts of background radiation. There is not any proven evidence that has established an increase in either human diseases or harmful effects when cumulative exposures are 10 times that of background radiation. Therefore, the very low dose of radiation you will receive when caring for your cat can be compared to a few months of our background radiation.

Do I need to wear gloves to pet my cat?

Not unless there is a chance that your cat has inadvertently soiled its coat with urine or feces.

What if my cat vomits within the first two weeks he/she is at home?

If your cat vomits, wear the latex gloves and clean up the vomitus with any cleaning agent you normally use. If you use toilet paper, flush everything down the toilet. If you use a cloth towel or paper towels, you will need to hold onto these towels in a separate, double-lined, garbage bag. After the 2-week period, you can throw it out in the garbage or wash it with your laundry.

Is the bedding, couch, carpet, etc. that my cat sleeps on going to become contaminated?

No, providing that he or she has not urinated, defecated, or vomited on anything.

How soon will my cat begin to gain weight and be back to her/his old self?

This varies; Some owners see changes in their cat’s weight and behavior immediately while for others it may take up to 6 months.

Download I-131 Information & FAQs


Starting Monday, April 8th through the end of September, the Illinois Department of Transportation (IDOT) will begin their road resurfacing project along Waukegan Road from Lake Cook Road to Half Day Road (IL 22). Please allow additional travel time to our hospital during the construction. Learn More: Waukegan Road Resurfacing Project