Diabetes melitus is a disease that cripples the body to metabolize and efficiently use carbohydrates, proteins and fats. When we eat, food (especially carbohydrates and fruits) are converted into glucose. All body cells need glucose to live, but glucose can not enter the cells without intervention of insulin. Insulin is produced in beta cells, which are located on the edge of the pancreas.
For example, when you eat a piece of bread, once digested is converted into glucose. Glucose circulates through the bloodstream to feed every cell in the body. The presence of glucose stimulates beta cells of the pancreas to release insulin. Insulin reaches every cell and acts like a key in their receivers, to open their doors and let the glucose enter. If there is no insulin or receptor cells do not function, the glucose can not enter cells, and the affected person will suffer from nutrient deficiencies.