... started me on Hydroxyurea 5 weeks ago. Today was my third blood draw, and my platelets are still over 800. Does anyone know how long it takes for the medicine to start bringing the numbers down? I have also been phlebotomized once during this time, and will be tomorrow as well. I was prescribed 500mg a day, then after being phlebotomized , they upped it to 1000 mg a day. Needless to say, I am very discouraged. Any info is greatly appreciated