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Oncology (General Cancer)/precautions after radioactive iodine therapy


You probably know that humans and cats are treated with radioactive iodine for hyperthyroidism. My cat is being treated next week, the facility specializes in the procedure, so I trust them not to release him until his radioactivity is low enough for him to come home. I plan to ask them the below questions but they are not experts in radioactivity.

I've searched the internet and some of the suggested aftercare precautions I've read are not specific. It states his urine and feces shouldn't be touched and should be sealed in plastic and stored outdoors for a month, we can do that easily. He's not supposed to be near children or pregnant women, that's no problem.

My concern is the advice to avoid close contact with him for at least 2 weeks, the guidelines are unclear. I understand we should avoid touching him directly. Everything that he uses or touches at the facility will be discarded of course but are the food and water dishes he uses during the 2 weeks also contaminated, or any clothing or bedding he contacts? Does normal washing with soap and water reduce or eliminate the radioactivity? Is there any specially protective clothing we can wear to minimize the risk?

Thanks for any advice.


I know this procedure well! My mother was treated with this method in the early 1950ies for hyperthyroidism and I do remember that well. And I have also myself treated a large number of human patients with this method in the 1970ies. Do not have the cat in your laps or close to you for a couple of weeks. Normal washing of the dishes is good enough to dilute and remove any traces from them. No special clothing is necessary. There is no need to be afraid if these simple rules are followed for a couple of weeks. Almost all radioactivity ends up in the thyroid gland of the cat. Small amounts in its salivary glands. Almost nothing in the rest of the cat. So there is no need to exaggerate any danger. The physical half life of the iodine isotope is short so it will radiate away fast. And on top of that there are also biological processes that will eliminate the iodine from the body of the cat. The combined effects of these processes will ensure that your cat is completely harmless after a couple of weeks. It is the simplest, easiest and fastest method of treating hyperthyroidism in both humans and animals. And also in fact one of the safest. Good luck!

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Oncology (General Cancer)

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Claes-Gustaf Nordquist, M.D.


Questions concerning Cancer, Oncology, radiation Therapy, Tumours, Chemotherapy, Cytotoxic Drugs, Hormonal Therapy, Radiation Protection.


I'm a Doctor of Medicine and specialist in Medical Oncology and Radiation Therapy educated & trained in Sweden. Now retired. Background in Radiation Therapy, Medical Oncology, Radiation Protection, Nuclear Medicine, Diagnostic Radiology, Gynecological Oncology, Clinical Pathology, Clinical Cytology,Hematology and Internal Medicine. M.D. from the faculty of medicine, Royal Karolinska Institute, Stockholm, Sweden. Have also been an exchange student at the Hebrew University, Hadassah Medical School, Jerusalem Israel. Former medical consultant, Swedish National Board of Radiation Protection. Former Police Surgeon and Medical Examiner, Stockholm Police Department. Former Chief Medical Officer, The Royal Guards, The Royal Horse Guards and the Royal Household Brigade, Royal Swedish Army Medical Corps. You can also reach me on: I have no restrictions in the number of questions there. I also answer questions in these other categories: General History, Military History, Brain Tumors, Breast Cancer, Colon Cancer

I'm a medical doctor and specialist in medical oncology and radiation therapy

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