How can high blood sugar levels affect erections?

High levels of insulin from overly high blood sugar actually create changes in parts of the sympathetic nervous system that send signals, making it difficult to get an erection, and we need some input from the other part of the nervous system (parasympathetic) to achieve an adequate erection. In other words, high levels of insulin like to turn the lights in the room on even when you hit the “lights off” switch. Also, high insulin levels cause blood vessels to constrict and reduce blood flow to the penis.