Primary care physicians can be great, I was diagnosed by mine, he really got me started off on the right track immediately and I responded well which was wonderful! They are wonderful for but sometimes people just have more questions and everyone is different so sometimes one person may not respond to the same course of treatment that works for most people. It sounds the numbers are not coming down as down quickly as the doctor would like. He or he/you tried a basic course of action that didn't work so time to see a specialist. That may be all there is to it. Endocrinologists specialize in diabetes, they go to school even longer. They see a lot more patients with the same problems, crunch a lot more numbers and have more different ideas and options for way to treat us as unique individuals with specific problems. An endocrinologist can help you specifically with the difficulties you are having. They really can fine tune they whole system. They look much closer I think is the biggest thing. As much as I LOVE my primary care physician and hated to not see him at my doctor visits, I really appreciate the additional help and information I have received  from the endocrinologist. Hope this helps & good luck!