Good morning, @willerta. It’s important that you don’t change any of your medications based on what someone in the forum has said. No one in our forum can diagnose or offer treatment for a disease or condition. What may work for one person may not be appropriate for others.
So please, continue to take your Vitamin B12 supplements as directed by your oncologist! This is the person you need to rely on to help you make the best medical decision, not members of the forum. They don’t know your whole story or medical history. Those decisions remain between you and your doctor.

Your new oncologist also recommended a bone marrow biopsy. Since you have a blood condition that is causing an overproduction of platetlets, your doctor is wanting to investigate the cause. The bone marrow is the heart of the blood manufacturing site in the body. By having a bone marrow biopsy, your doctor will be able to get a clearer picture of the over all health of your marrow and its ability to produce healthy blood cells. You can ask your doctor what they hope to gain with the biopsy and if it’s necessary. But if they recommended it, I hope you decide to have it done because these aren’t done for frivolous reasons.

Please, again, don’t let advice from others in the group misdirect you or cause you to have doubts about your own doctor.
Certainly if you’re not comfortable with your doctor for some reason or want a second opinion, that’s always a valid concern. But sometimes even well-intentioned comments can plant a seed of doubt in our minds which isn’t warranted.

I hope you continue to take your Vitamin B-12 now…there was a reason your doctor prescribed this dosage. Do you feel more comfortable about taking them now?