Differences between the pump and multiple daily injections

With multiple daily injections you use two types of insulin. A long-acting insulin (slow analogue), given once or twice a day, covers the background need between meals and during the night. A rapid-acting insulin (rapid analogue) is given before every meal and to correct a high blood glucose [1]. Every dose means a separate injection, at a well-established moment.

The pump delivers only rapid-acting insulin (rapid analogue), also subcutaneously, through a thin cannula [2]. The pump provides a permanent background flow, through the basal rates that you can set differently across the day. At the meal you give a bolus by pressing a few buttons. You no longer need long-acting insulin. A pump can be linked to a glucose sensor, which thus helps to regulate insulin delivery automatically [3].

With the pen you prick yourself several times every day, practically for every delivery (unless you use an injection port such as i-port, a cannula taped to the skin through which you inject for a few days without new pricks). You need one injection for the basal insulin, plus one injection before every meal and for corrections [1]. In total you generally reach 4-8 pricks a day, day after day.

With the pump you insert the cannula (one prick) and you change it every three days (sooner if needed) [4]. Between changes you deliver the insulin by pressing a few buttons, without any other pricks. In this way the number of pricks for delivering insulin drops enormously compared with the pen. If you also wear a glucose sensor, it has its own separate prick when it is inserted, but the great majority of the pricks with the glucose meter disappear, as the figure below shows [3].

In day-to-day use, no. The pump covers both the basal insulin and the insulin for meals, so you no longer need daily pen injections as long as the pump is working well [2].

Even so, always keep within reach a pen or a syringe with rapid-acting insulin and, separately, long-acting insulin, as a backup. If the pump breaks down, you will have to switch quickly to injections. Blood glucose and ketone bodies can rise very quickly when insulin delivery is interrupted, especially at night [5]. The reason is that the pump uses only rapid-acting insulin, without a long-acting reserve.

Yes, usually you have more freedom. You can give the dose for the meal by pressing a few buttons, more easily and more discreetly than preparing a new injection. The pump calculator helps you work out the dose, starting from the amount of carbohydrates and from the current blood glucose [6].

In addition, you can spread the dose over a longer interval, for meals rich in fat and protein or for meals that last longer [7]. The basal insulin flow provides a foundation that allows you to eat at variable hours. You only have to give a mealtime dose before the meal [8].

With multiple daily injections, the basal insulin dose provides a relatively fixed insulin flow for the whole interval it covers. Adjusting the dose is done by injecting a different amount the next time, and the change in dose influences the following 24 hours fairly uniformly. The mealtime doses you calculate from the insulin-to-carbohydrate ratio and from the correction factor, and then you give them with the pen [1].

On the pump, the basal insulin flow is set through the basal rates, which can differ from one hour to the next [9]. For example, you can schedule more insulin in the early morning and less during the night. You can also set a temporary rate, higher or lower for a few hours, for sport or during an acute illness [10]. A pump linked to a sensor, working in closed loop, can regulate the basal insulin flow on its own and can give repeated automatic corrections [11]. Injections cannot do this.

At the beginning yes, you have more to learn. The pump is a device with menus and settings, such as the basal rates, the insulin-to-carbohydrate ratio and the correction factor. Added to this are inserting and caring for the cannula, filling the reservoir and responding to alarms. You need training and support from your diabetes team [12]. After you complete this training, also known as pump school, you will see that the daily management of diabetes becomes easier and more convenient.

You have fewer injections, you give the boluses by pressing a few buttons and you use a bolus calculator that is generally very useful. You also have to know how to react when something breaks down, to have a backup plan, including for a temporary switch to injections if needed [3]. Injections are simpler to learn at the start, but they limit you in interventions over the long term.

No. The continuous flow of basal insulin covers your needs between meals, so you are not obliged to eat at fixed hours in order to match the action of the insulin [8]. You can postpone, move or skip a meal more easily.

When you eat, you give a bolus for that meal and you work it out from the amount of carbohydrates you actually eat; if your blood glucose before the meal is high, you add a correction dose to that bolus. This is one of the freedoms of pump treatment. With a closed-loop system, the basal insulin flow is regulated automatically, but you will still have to announce the meal by giving a mealtime bolus [13].