I know this is different for everyone, but my son Connor (age 4) gets very sick, very fast. The beginnings of a crisis with him have usually been due to a fever. (d/t an ear infection, virus, strep throat) He usually starts vomiting almost continuously and gets extremely lethargic. I always try to triple the oral dose of Hydrocortisone, but then if he vomits again, he gets the injection while we are on the way to the Emergency Room. He has been so lethargic by that time that he doesn't even fight me when I give the shot. One time it was as quick as 20 minutes from the time he began vomiting, to the time I had to give the shot, and I had to continuously stimulate him to keep him conscious. He has had to have IV fluids and maybe 2 or 3 doses of the Solu-Cortef, but then he snaps back rather quickly. It is frightening and feels like a roller coaster sometimes, but I always get him medical attention fast. I compare it to the way people describe "brittle" diabetics compared to diabetics that stay in good control. Everyone's body reacts differently. I have just learned with Connor not to EVER take any chances or wait it out at home.