I have been on Hydrea all but one year since 2001, and it has been very effective for me . There are other longtime Hydrea users on this site, as well. Some of us have other medical issues which contraindicate certain treatments. It is important to find a provider you trust, and talk with them about which medication is best for you, and why.

My grandson is only 16 and takes high doses I'm very concerned for his future on this medication

I'd never take this drug. It kills bone marrow... thereby reducing your Hg, platelets and anything else.
There are other ways to achieve the result without adverse effects. One is ivermectin which kills all abnormal cells without destroying bone marrow. You'll never get your oncologist to prescribe this because it is not on the "standard" treatment protocol and they are not going to risk their medical license for you.

If your goal is to decline gradually while living off of whole blood transfusions, take the hydroxyurea. If your goal is to recover and lead a near normal life, find another way.

Oncologists do not believe anyone can recover from MDS or MPN. They view their job as "managing your decline" until oblivion sets in.
Those are your choices, I pursued option #2. My Hg is 14.0 and platelets dropping. Other blood products normalizing.
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Yes, it is.