What dosage have you been prescibed? ET patients usually only need very low dosages of hydrea. Be sure to drink plenty of water (I drink at least a litre daily) to help flush the med and keep any possible side effects to a minimum. If you get mouth sores, up your intake if water a bit and rinse your mouth with salt water or a good mouthwash. Hydrea will bring out any former sun damage you already have and will likely cause sensitivity to the sun, so be sure to wear protective clothing and a good hat if you need to be outside during the day when the sun is at it's peak. I've had JAK2 positive ET and have taken Hydrea for several years now and my platelets are in the normal range. I rarely have any side effects from the meds.