A "safe" platelet count usually takes into consideration age, driver mutation, and clot history.

Somebody in their 40s with CALR mutation and no clots might be allowed to ride to 1,000 with just aspirin. Somebody over 60 with JAK2 and deep vein thrombosis might be given aspirin plus enough HU to get platelets below 400.

Oncologists who deem a patient at high risk for clots, regardless of platelet count, may front load a higher dose of HU to get count down and then lower the dose when platelets are at acceptable levels. These patients might experience most drug side effects.

Oncologists who deem a patient low or moderate risk might start patients on low dose and increase over a period of months as needed.

There is really no one size fits all approach. So it's helpful to me when people include their age and mutation with comments here. (I'm 70, CALR, no clots.)

I was under the impression when I was first diagnosed that the higher my platelet count the higher my clot risk. Doc said it's more complicated. Anything over 450 increases risk. Anything over 1,000 increases bleeding/von Willebrand risk. In between, the rising or falling counts indicate whether your disease is progressing or your meds are working.