I was so cross at being fobbed off by a registrar who wanted me out of the consulting room as quick as possible, that I emailed a letter to the consultant I was supposed to see. I was not rude, I just stated the facts and then gave my clinical symptoms and that I wanted a full discussion on my treatment if possible. The email was sent at 8.30am and at 4.00pm the consultants secretary rang me to apologise on his behalf and arrange blood tests and a proper consultation.
It's worth putting things in writing if you are not happy.