My Mom Is 80 Years Old Have Been On Insulin

My Mom is 80 years old have been on insulin for over 30 years. They have decided to put her on pills pranadine. Won't her body go into shock after using insulin for so many years and now suddenly she is back on pills. Initially when she was diagnosed they put her on pills and she kept passing out at work and that's when they decided on insulin. What are your thoughts?