I really have to agree with TJF on this..... go over all the information with your GI because your GI will have a lot of first hand knowledge about
6-mp because many of his/her patients are probably using 6mp/imuran. If your GI does not have many patients on 6mp/imuran I would suggest finding another GI. Many IBD'ers seek out a second or third opinion from other GIs when it comes to starting immunosurpressents because it is a big step in the course of living with /treating an IBD. I would suggest reading this topic https://www.healingwell.com/community/default.aspx?f=38&m=1055869
there is a great article included in the topic.
Remember you have the right to refuse medical treatment if you are not comfortable with it.