 [ Symptoms ] if my prescription says twice a day or every 12 hours can i take it even if there is more than 12 hours in between [ Disease ] the reason why a prescription maybe dosed 12 hours is that is what was done in the studies and that is how we know the drug works and how it is going to be effective so if you extend that timeframe the drug may not work as well you may not feel better because the drug needs that constant blood level in your system so in the beginning once every 12 hours you are taking it faithfully it creates what we call steady levels if you tend to forget a dose or take it a lot later you might actually break up that steady dose of the medication and therefore that could lead to an increase in side effects or do not help in infection or blood pressure or something else so you really want to adhere to the dosing schedule that is on that particular prescription bottle if you have any questions ask your pharmacist