Basal insulin refers to the insulin required to control your blood sugar in the absence of food intake. A certain 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 injection 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 prevent the blood sugar from rising excessively after a meal, while also preventing the occurrence of low blood sugar after the glucose from the meal has been cleared from the bloodstream.
The latest insulin pumps offer different rates and patterns in which this bolus is given, in order to more effectively deal with rapidly or more slowly absorbed types of foods. Figure 4 shows the normal pattern in which the body releases insulin and describes how basal, bolus, and supple-mental insulin are given to mimic this as closely as possible. 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 preparation will overlap with each other in their action.