Yes. Heroin can cause hyperglycemia because heroin stimulates the sympathetic branch of the nervous system. This branch is responsible for the constricted pupils and fast heart rate you see in heroin overdose. The high blood sugar is due to the increased demands of the cells because the metabolic rate of the cells is increased. Therefore, the sympathetic nervous system stimulates the release of stored sugar from the liver and it enters the blood stream. This causes the hyperglycemia.