MODEL RELEASED. Injecting insulin. General practitioner instructing his patient to use an insulin pen. He has diabetes mellitus. This is a disorder affecting glucose sugar metabolism, where sugar is not oxidised due to a lack of the pancreatic hormone insulin. Unused sugar accumulates in the blood and the urine. Fats are utilised as an alternative energy source, which leads to a build-up of ketones in the blood that may eventually cause convulsions and diabetic coma. Treatment is based on a strict diet and the use of daily insulin injections to maintain the blood-sugar balance.