The main reason we say empty stomach is that if there are bread or grains in your stomach they may absorb the Iodine and hold on to it for the two or three hours that the Iodine is in the nascent state. The time that the Iodine is in that nascent state, it can do great deal of work in the body. That is why many people divide up their dose into three parts so the time active in the body is longer. Most do not take after supper so as to not interfere with sleep.