Basal insulin refers to the insulin required to control your blood sugar in the absence of food intake. A cer- tain amount of insulin is always necessary to keep the blood sugar in the normal range, even in the absence of eating for prolonged periods. Without any insulin in the body, the starch, fat, and protein in the body will break down with severe health consequences, as occurs in people with type 1 diabetes. The amount of insulin that the body requires in the absence of food intake is known as the basal requirement and it is pro- vided by the one or two injections of long-acting insulin that most patients give themselves each day. If a person is using an insulin pump, then it is covered by the basal setting on the pump. Modern insulin pumps offer several basal settings in each 24-hour period, as the basal insulin production in a healthy individual varies over the course of the day, being higher in the 2-to 3-hour period before arising in the morning, for example.
Bolus insulin refers to the insulin required to remove the energy derived from a meal from the bloodstream and into the tissues, to replenish energy stores. This is typically provided by the short-acting insulin injec- tion given just prior to eating or by the bolus setting for patients on an insulin pump. Recently developed and marketed forms of insulin very closely match the pattern of insulin production from the pancreas itself in response to food. In this way, they are able to
Of course, once it has been delivered to the body, the insulin cannot distinguish between basal and meal- derived glucose and so different types of insulin prepa- ration will overlap with each other in their action. Distinguishing between the two requires specialized knowledge and is beyond the scope of this book.