Used these in late 2014 after my cat had "Radiocat" - radioactive iodine therapy for hyperthyroidism. The cats are at a "safe" level of radioactivity when they are released, but we were told a list of things to do for two weeks, like we can't throw away litter, because it's too radioactive to go to the landfill, so flushable has to be used, etc... Most importantly, we were told to "limit" our interactions and not let them sleep on the bed.. etc.. So - basically, I was like "yeah, no... that's not possible" lol. Just for "good measure" I took these every day for the two weeks after my cat came home, just to be doubly sure that his slight radioactivity with I-131 wouldn't affect my thyroid at all! Didn't have any problem with the pills. It might have been overkill, but hey, for less than ten bucks, it was totally worth it. I have another cat who will be getting the same treatment in January 2018, so I'll be buying these again