When I started on Hydroxyurea my platelets were at 891…. but the drug brought them down right away by 100 points in one week to 790. I had blood tests once a week for 3 months and now have them once a month. Platelets continued the downward trend but much more slowly. I am now back up to 455 after having been as high again as 600, and as low as 375. My monthly draw is scheduled for next week, so I am anxious to see if I am back within normal range. I guess what I am saying though is that platelets can fluctuate even when on medication. But I am grateful for the meds because I don’t seem to have many side effects. ( Maybe just more tired than I used to be….but I am approaching 70 years old too! 😉)