Forms of insulin delivery

Photo of insulin being injected (PantherMedia / Dmitry Lobanov)

To be able to work, insulin has to enter the bloodstream. It can't be taken in the form of tablets or capsules because then the hormone would be broken down in the stomach. There are a number of ways to get insulin into the blood.

Insulin is usually injected into fat tissue underneath the skin (subcutaneously). From there it is gradually absorbed into the bloodstream and is carried around the body. In Germany, the most common way to inject insulin is using insulin pens and insulin pumps. Not many people inject insulin using actual syringes.

People can decide whether they would like to use a syringe or pen based on their own personal preferences. There is no known medical reason for choosing one option over the other. Research has found only minor differences in terms of how well they regulate blood sugar levels. Blood sugar control is somewhat better in people who use pumps. But there is not enough good research to be able to say whether pumps have any long-term health advantages or disadvantages compared to syringes or insulin pens.

Syringes and insulin pens

Although many people have a problem with the idea of injecting themselves at first, it's relatively simple and hardly takes a minute with a little practice: You prepare the vial, draw the insulin into the syringe, inject it, and put the instruments away again.

Insulin pens are even easier to use. They are about the size of a large ballpoint pen. They contain insulin-filled cartridges that last about a week, depending on how much insulin is used. You can easily set the number of units you want to inject. The insulin is then injected through a thin needle by pressing down a button. With a bit of practice it is even possible to do things like inject insulin at a restaurant table without others noticing.

There are also disposable pens that are pre-filled with insulin and can be thrown away after use. Various refillable pens are available too. Insulin manufacturers often give these away for free. If you decide to keep a free pen, you will only be able to use the insulin produced by that manufacturer. Because the shape of the insulin cartridges and the way the needle is attached varies greatly between different pens, it is not possible to mix and match different manufacturers' pens and cartridges. So it can be worthwhile to look at various pens and try them out before making a final choice.

Insulin pumps

Modern pumps are slightly bigger than a matchbox. Each pump consists of a reservoir filled with insulin, a battery and a small computer. To use the pump, you insert a special thin needle into a suitable area of skin, like you do when injecting insulin with a syringe or pen. The needle is then fixed in place using an adhesive bandage, and is attached to a thin tube (catheter) that leads to the pump. The needle can be left in the same place for one to two days. Then the needle and catheter should be replaced and re-inserted somewhere else on the skin.

Insulin pumps have two main functions: On the one hand, they are programmed to cover your basic insulin needs (basal rate) by regularly delivering small amounts of short-acting insulin. On the other hand, you can press a button to deliver extra amounts of insulin (bolus insulin) at mealtimes, just like you can when using a syringe or insulin pen. This needs-based insulin therapy helps to prevent strong blood sugar fluctuations.

Because the pumps need to be programmed, some knowledge is required. To use the pump properly, you also need to have experience with intensive insulin therapy, regular blood sugar monitoring and adjusting your insulin dose. Studies have shown that in order to effectively avoid high and low blood sugar, people who use a pump have to be very familiar with their diabetes.

Pumps are not necessarily the best option for everyone with diabetes. Many people prefer to inject insulin several times a day rather than using a pump. Not everyone feels comfortable having a needle in them and wearing a pump all the time.

In Germany, pumps are often used specifically for patients who have major fluctuations in their blood sugar levels – for example, they may have levels that regularly rise steeply in the early morning hours. This is known as “the dawn phenomenon.” Pumps are also suitable for people who want to be very flexible, for example because they are particularly physically active. Women who are planning to get pregnant or are already pregnant often choose to use an insulin pump too.

Statutory health insurers in Germany cover the costs of insulin pumps if you:

  • experience major fluctuations in blood sugar levels
  • regularly have severe low blood sugar, particularly at night
  • do not easily notice when your blood sugar levels are low
  • are pregnant or would like to become pregnant

Blood sugar control is somewhat more effective with pumps than it is with syringes or insulin pens. But there is no proof that this leads to fewer episodes of low blood sugar during the day. The studies do, however, suggest that episodes of low blood sugar at night are less common when insulin pumps are used.

There is generally not enough research on the long-term health benefits or disadvantages of pumps compared with syringes or pens. Pumps probably do not offer a dramatic improvement in diabetes treatment. Instead, they are a useful alternative for people who have particular problems or preferences. People who use insulin pumps over longer periods of time are generally satisfied with their pump. This is also true of parents whose children use an insulin pump. They feel that pumps give the whole family greater freedom in everyday life.

Other forms of insulin delivery

Not many people with diabetes use what are known as jet injectors. With jet injectors, the insulin is injected through the skin using a high-pressure air mechanism rather than a needle. They are quite a lot bigger and less user-friendly than insulin pens, and it is more difficult to get the dose right. It is not clear whether they offer any advantages. They are more expensive than insulin pens or syringes.

Other forms of insulin delivery are currently being developed and tested. These include insulin pumps that are implanted under the skin and patches that deliver insulin which is absorbed through the skin.

Insulin can also be injected directly into a vein in emergencies, when an immediate effect is needed. This should only be done by a doctor, though.