Hi Grizz, I tried that and it stayed there for nearly 2 days, it got fainter over time but I could still see it. When they painted my leg with it in hospital it took several days to go, although that was about 30 years ago. I am not sure how accurate it can be? I know I am Iodine deficient, I had no Iodine rich foods or iodized salts for years and have had a lot of exposure to chlorine/fluoride until I knew better. I am finding the whole thing most frustrating due to lack of availability of testing and decent doctor's in the uk. For arguments sake, if you were Iodine sufficient, what would be the consequences of taking high doses? Thanks, sue