What may cause elevated B12 and ferritin readings in a blood rest?

You did not ask the doctor?

An elevated B12 level is of no concern. Only reduced B12 levels are of note. An elevated ferritin level means that you may have elevated iron stores. Most of the time, this is also of no major significance. Many older individuals or people with chronic health problems of any sort have elevated ferritin levels (it is a response to physiologic stress including, in some cases, advanced age). If it is only mildly elevated, I wouldn't worry. If it is markedly elevated, and you are not elderly or have any chronic diseases, you might talk with your doctor to make sure you don't have a genetic disease causing over-accumulation of iron.