Insulin is a hormone produced by specialized cells in the pancreas. Secreted into the bloodstream at each meal, insulin helps the body use and store glucose (sugar) produced during the digestion of food. In people with diabetes, the pancreas either does not produce enough insulin or the body cannot use the insulin that is produced in an efficient manner.
Treatment for diabetes requires the delivery of insulin into the bloodstream by either an insulin pen, needle and syringe, or pump. An insulin pen is a device that looks like a pen but contains an insulin cartridge. Both the syringe and pen methods require injection of the insulin into the arm, thigh, or abdomen. Pump therapy, however, continuously administers insulin according to a programmed plan unique to the pump wearer. Several types of insulin exist, and they differ in when the insulin begins working after it is injected, when the insulin is working hardest, and how long the insulin lasts in the body.
Insulin release and glucose absorption depend on a number of factors, including the glycemic index of food and the co-ingestion of fat and protein. Consumption of high-glycemic foods causes hyperglycemia which results in the release of too much insulin. On the other hand, low-glycemic foods or the ingestion of fat and protein in a meal provide steady glucose absorption and release of insulin.
Exercise lowers blood glucose levels and increases the amount of insulin in the bloodstream, along with improving the body's use of insulin. A balance must exist between the sugar used for energy, the sugar available from food, and the insulin used in lowering blood sugar. Consequently, changes may have to be made to insulin, or food intake, or both, prior to and after exercise.
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American Diabetes Association. "About Insulin." Available from <http://www.diabetes.org/>
National Library of Medicine. "Diabetes." Updated July 2, 2003. Available from <http://medlineplus.gov/>