There are secondary upturn concentration of this hormone in the blood takes place between 12 and 1:00 pm and between 5:30 and 6:30. From that standpoint, the dose of morning coffee will be more effective between 9:30 and 11:30 am. On the other hand, the dose of afternoon coffee will be more effective between 1:30 and 5:00 pm. These are the two time lapses of the day when cortisol levels are lower and coffee will potentiate its effects. This might help you figure out what is the best time for coffee.