I'm 70 and very active. I was diagnosed with ET in November, 2023 and have been on HU ever since, starting at 500 mg 2x a day, every day. As my platelet count came down, my dose was reduced to 2x a day, 4 days a week. I have had some hair loss - more at the beginning and it slowed down as the dose was reduced. I can now see a lot of new growth right around my hairline. The hair loss wasn't so bad that you could see my scalp, but I could tell by feeling it that I had less hair. In the grand scheme of things, I'll take hair loss over an early death from a blood clot - although I understand the vanity aspect, too. Not everyone has this side effect, or any others - we all react differently to medications and I'm hoping that you will experience very few or none at all.