What are the routes of administration for insulin?

Insulin is only available as a liquid preparation.

Depending on different circumstances it can:

Injecting insulin subcutaneously

How insulin is supplied

There are several means by which it can be supplied for use subcutaneously (in the skin):

  • It can be drawn out of an insulin vial ONLY using an insulin syringe.

Using an insulin syringe to draw insulin out of an insulin vial Figure: using an insulin syringe to draw insulin out of an insulin vial

  • It can be provided as a prefilled pen device, which is disposed of once empty.

  • It can be provided as a cartridge that can be loaded into an insulin pen.

Insulin should never be drawn out of a cartridge using a syringe.

Picture of insulin cartridges and incorrect usage Figure: insulin should never be drawn out of a cartridge using a syringe

How insulin should be administered subcutaneously

  1. When insulin is to be administered subcutaneously by injection, the injection site should be clean and the person giving the insulin should wash their hands.

  2. In the UK, 4-6mm sized needles tend to be used most commonly.

  3. Prior to each administration, usual advice is to draw up insulin or dial up the dose using an insulin pen. The user is then asked to perform an ‘air shot’. This is where 2-3 units are discharged into the air to ensure that the syringe or insulin pen are working correctly.

  4. Provided that this demonstrates insulin release, the required treatment dose can then be drawn or dialled up.

  5. The appropriate injection site is then chosen.  

  6. The recommended sites for insulin injection are abdomen, buttocks and thighs. Once the site is chosen, the skin should not be pinched up prior to injection unless the person has been advised to do so.

  7. The insulin is administered at a 90% angle and the user typically asked to keep the syringe or pen plunger fully depressed for 6 to 10 seconds before withdrawing, which seeks to ensure that all insulin administered is delivered subcutaneously.

  8. Injection sites should always be rotated to prevent lipohypertrophy. This is the growth of local fat in the skin as a consequence of the anabolic property of insulin which can impede the absorption of insulin and hence its action on lowering blood glucose levels.

  9. The needle must then be disposed of in a safe manner using an appropriate container. 

Administered by personal insulin pump

For patients with type 1 diabetes, a pre-filled insulin cartridge can also be inserted into a personal insulin pump.

This device is permanently worn by the patient and constantly delivers an infusion of insulin, at a rate defined by the user.

Picture of insulin pump Figure: fitting a wearable insulin pump

The cartridge is changed every few days.

In the United Kingdom, only people with type 1 diabetes who meet essential criteria are entitled to a trial of insulin pump therapy.

Did you know? New technology called the ‘artificial pancreas’ has been shown to be effective in controlling blood glucose concentrations in people with type 1 diabetes, including pregnant women.

This system continuously checks blood glucose levels and the calculates how much insulin is required before automatically delivering the correct amount of insulin through the pump. This leads to improved glucose control.

Administered intravenously

If a person in hospital is unwell with uncontrolled high blood glucose levels, insulin can be administered through an intravenous insulin infusion. It is only rapid or short acting insulin that is administered by this route.

The hourly rate of insulin infused is adjusted depending on the measured venous blood glucose per hour. The aim is to keep blood glucose levels at a safe level.

Did you know? If the patient is not able to eat and drink, it is essential that the insulin is administered together with intravenous glucose based fluid, as the insulin needs glucose to work as a substrate to push into cells to use for energy. In this situation, without glucose, there is a risk of hypoglycaemia

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This article is from the free online course:

Understanding Insulin

University of Southampton