Rises in blood sugar after surgery are common and when they rise too high it increases the risk of infection and other complications. On the other hand, doctors are moving away from very tight glucose control, because it doesn’t offer any advantages and may increase the risk of hypoglycemia.hen diabetics are stressed for any reason, their body pumps out hormones that alter blood sugar levels – causing blood sugars to go up or down. Sometimes medications doctors give during or after surgery, particularly steroids, cause blood sugar levels to rise.