In non-diabetic people, the pancreas continuously produces small amounts of insulin to maintain physiological functions, and after food intake, a larger amount is produced. In diabetic people this function is altered and has to be supplied exogenously.
The insulin pump quite successfully mimics the function of the healthy pancreas, automatically releasing small amounts of rapid-acting insulin every few minutes. This is what is called a basal infusion. With the basal infusion, insulin needs are covered between meals, and during sleep to keep the blood glucose level constant in addition to supporting other physiological functions. In specific cases, the basal infusion can be temporarily modified to, for example, cover an unscheduled physical exercise or overcome an intercurrent illness.
When ingesting food, the user will have to give boluses of insulin.The bolus is the amount of insulin necessary to metabolize ingested carbohydrates.
When a pump is not available, attempts are made to mimic the function of the pancreas through multiple injections, combining rapid and long-acting insulins such as glargine, detemir or degludec. This combination provides a relatively uneven flow of insulin into the bloodstream and a non-constant and continuous flow like that obtained with the pump. These insulins, although they barely have a peak of action, contrary to what happened with NPH-type insulins, do not allow their effect to be modulated by increasing or decreasing availability to adapt to specific needs at all times and also, the duration does not adjust to periods of 24 hours making its dosage difficult in practice.