That is a good question and one I have never really asked about. I can tell you what I have done. When my son broke his leg (it was only a guess before we went to the ER), it was about 7pm.....hours before his nighttime dose. I went ahead and doubled the dose eveing dose and geve it then, gave tylenol for pain and went to the ER. Even if he had not broken his foot, he was crying so much, I was concerned that he was getting himself really worked up. When we have had fever of 101 and above, I double the next dose he is supposed to have and count that as that dose. Most stress doses are supposed to be given for 24 hours....meaning, if you take 3 doses, you double/triple those three doses. I hope that helps.