I Recently Had My A1c Test Come Back As 5.7%,

I recently had my A1c test come back as 5.7%, which is pre-diabetic. I was given a cortisone shot for an allergic reaction to a antibiotic and I know that cortisone can elevate glucose in the blood. Did the shot of cortisone affect my A1c test? Also would an autoimmune disease like mixed connective tissue disease cause diabetes due to the immune system attacking the pancreas? I found information that many lupus patients are also diabetic.