Olivia's ped endo and endocrine nurse have both said to give the dose when you discover it was missed, but not if too close to the next dose. This has always seemed logicial to me. If the body isn't under stress (or has no symptoms to indicate that there is a problem) at the time, there is no need to double dose. I think there has been 2 or 3 times that I have forgotton to give the afternoon dose -- but have always remember within 2 hours of when it should be given.