Its more complicated than that. It involves not only the time of the exam, but how you react to the meds, when you take the meds, on an empty/full stomach, etc.
Read the links below on to Find Those Effective Sides of the Therapeutic Window:
Also use the "search" window. type in concerta for more info on the Corepsych site.
And you might do even better taking a short acting ritalin if your test is later in the day, rather then another XL. This link is very good about getting extended coverage from different meds (concerta does not appear to be one of the best to take for longer coverage) http://www.corepsych.com/2008/11/add-adhd-stimulant-medication-dosage-the-bottom-bewitching-hours/
Notice that I am assuming the problem is that the med doesn't last long enough. If the med isn't working for you then there is a 54mg pill or perhaps another med. At any rate, this is something that you want to talk over with your Doc. and do on his advice. Best wishes.
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