This is an excellent question. Vitamins and isotretinoin can be tricky. B12 in general can actually be traced to acne flare ups. Isotretinoin can decrease B12 levels. Low B12 can be problematic. But generally is isn't recommended (B12) to be taken with Isotretinoin very often. I am glad you are followed by a doctor, is he the one who prescribed the isotretinioin? And why are you having the B12 added? I would talk to them about it as well as ask your usual pharmacist. I would be hesitant to add it myself. Here is some reading on the subject: https://www.pharmacytimes.com/resource-centers/vitamins-supplements/isotretinoins-role-in-acne-and-vitamin-b12