Atrial fibrillation can cause major hyperglycemia.

We report the case of a 66 years old woman with a well controlled, insulin-treated, type 2 diabetes, who experienced a ten-fold increase of her daily insulin needs (from 21 to 215 U/day) after the onset of a symptomatic atrial fibrillation. Check-up for another cause of insulin resistance was negative, and insulin doses could be decreased to preceding values only after electric cardioversion. Symptomatic atrial fibrillation should be considered as a potential cause of hyperglycemia.