My ped endo doesn't say to fast, but we give meds at 6 a.m. and have the blood drawn between 8 and 9 a.m. Unfortunately, we had his blood drawn this past Thursday and they couldn't get his blood until the fifth time they stuck him, so his renin and CAH profile wasn't gotten until 9:15 a.m. They did manage to get enough on the third try for his electrolytes. What a nightmare that was.