20 month old had high fever of 40. got it down and she is sleeping. it is now back up to 38. should i wake her for meds or let her sleep?

Let her sleep: Fever is a natural body response to illness that increases the heart rate & movement of white cells & antibodies that fight illness. Sleep is a natural response to the need for the additional work. I NEVER wake a sleeping child for fever meds. If they are awake & it is dose time, I may or may not give it bases on their level of comfort.