@jodyjazz my highest was around 750,000. I had a number of symptoms at that level so I went on HU. I was 69. Your count seems on the low side. Did you have symptoms or blood clots?

@jodyjazz I've noticed most people on this site have started treatment earlier. I'm in Australia and was diagnosed with ET Jak2 in August 2025. Here is what my haematologist advised me. Starting treatment differs by country, Australia is more "conservative", starting around 1000, the US are more "aggressive" starting around 500. It's all about the risk factor and how it's determined, ie. stroke risk increasing from age 60 and then factoring in other contributors like high blood pressure and/or heart issues. I am 60, on medication for high blood pressure and am in the medium risk for heart disease. Both are being managed. I haven't had any previous blood clots. My platelets are at 920. Assuming it's standard everywhere but normal range in Australia is between 150-450. He also said the 100mg aspirin renders half of the platelets "helplesss" so my count is more like 460. I did not have a bone marrow test so not sure if that shows other information to factor in when to start treatment. I have blood tests every 8-12 weeks. I'm really on the cusp of starting treatment and was given the choice to start now or wait to see my blood results later this month.

@jodyjazz Starting HU depends on 3 things: Driver mutation, age, and clot history. Some young folks who have never had a clot and are CALR+ are started when platelets are 1,000. Patients over 60 with JAK2 and a clot go might go on HU at 500.

Everybody goes on aspirin, because that's the best preventive for clots. And no clots, no HU, at least for awhile
Patients who cannot take aspirin often take a substitute blood thinner.

I am CALR+. At 64, I was started on 500 mg of HU daily when my platelets started creeping up to 800 pretty fast. I've never had a clot, but if platelets go over 1,000 the docs start worrying about your developing von Willebrand's Syndrome, which can cause bleeding.