A hypnotist may well have the ability to remove or reduce your anxiety with the information you have given. I don�t believe it has to be specific.
However, hypnotism does not work for everyone. Perhaps if you could explore further why you think you have this phobia (needles, blood, situational). There are specific types of blood test phobias such as hemophobia, hematophobia, hemaphobia and most commonly the fear of blood, so it is not uncommon.
It is likely that the hypnotism may focus on the situational anxiety and try to make you feel at ease when the situation arises.