How long will it take before I can start on accutane?Please answer..?

I have an appointment for next friday, but I know I have to get a blood test before I can start on it..It's just I am in so much pain..I have had this really bad cystic acne for the last few months, but lately it has just got so bad..I can't sleep properly because when my face touches the pillow it stings, and everytime I move my neck it hurts so bad because I have these cysts on my jaw line and neck..I have never been in so much pain from pimples ever! I have already been waiting over a month for the dermatologist apointment, since they were all booked out..I dont want to have to wait ages again aftter the blood tests...I know it's not really that long, but when it's this painfull, even just one day seems like forever...I am not over exagerating, it is really painfull..So how long after I get the blood tests would I have to wait? Would I have to make another apointment? This is in Australia by the way..