There are three groups of insulin:
- Animal – this was the first type of insulin to be given to humans. Pork and bovine insulins have now been mainly replaced by human and analogue insulins
- Human – identical to human insulin but produced in a laboratory
- Analogues – these are modified or chemically altered versions of human insulin, altered to make them either more rapid or more smooth acting
There are six main types of insulin
- Rapid acting analogue insulin – are clear in appearance and are given just before, with or just after food and have a peak action of 0 to 3 hours. They last between 2 and 5 hours, working for the meal it has been taken for.
- Long acting analogues – are clear in appearance and are injected once a day to give a background insulin lasting around 24 hours. They do not have a peak of action so do not need to be taken with food.
- Mixed analogues – this insulin is a combination of short and long acting insulins. If there is a number in the name this is usually the percentage of the mixture that is short acting insulin
- Short acting insulins – are clear in appearance and should be given 15 to 20 minutes before a meal. The peak action is 2 to 6 hours and can last for up to 8 hours
- Medium and long-acting insulin – are cloudy in appearance, their peak action is 4 to 12 hours and can last up to 30 hours. They are sometimes given with tablets or in combination with a short /rapid acting insulin.
- Mixed insulins – are cloudy in appearance and are a mixture of short and long-acting insulin.
How does it work?
Insulin is injected just under the skin (subcutaneously) with very fine short needles. It is not injected into the muscles or veins.
Once the insulin has been injected under the skin, small vessels absorb it into the blood stream where it is then used by the body to reduce blood sugar levels.
Where can I inject?
There are four main recommended injection sites
- arms – this site is best avoided if you are very thin or very muscular
It is important to rotate your injection sites, in other words move around within the area as well as using a different area.
Failing to do this can cause the build up of lumps under the skin called lipohypertrophy. This can make the skin texture feel or look lumpy. It can also mean the insulin gets stuck or isn’t absorbed properly and so can lead to unstable blood sugar levels.
If you use two different types of insulin, it is important to keep your injection sites separate.
The doctor or nurse will ask to examine your injection sites at every annual review appointment.
Needles and disposal of sharps
Needles are designed for single use. Using them more frequently will cause damage to the skin where you are injecting and can make it painful to inject.
Once you have given your injection, it is important to remove your needle and dispose of it safely in a sharps bin.
Leaving your used needle on your injection pen can lead to insulin leaking out of the pen.
Giving an injection
- Put a new needle on your injection pen. Remove the large cap and keep to one side, remove the small needle cover and discard.
- If you are using a mixed insulin, mix it by rotating or twisting the device.
- Dial up 2 units and press the plunger to eject the insulin. This is an “air shot” to make sure insulin is coming through the needle.
- Choose the area you are going to inject. Only pinch up the skin if you have been advised to do this by your doctor or nurse.
- Expose this area of skin, do not inject through clothing because the needle might pick up fibres from the clothing and damage the needle.
- Insert the needle into the skin at a 90 degree angle.
- Press the plunger to inject all the insulin.
- Count to ten.
- Remove the needle from the skin.
- Remove the needle using the large needle cap and dispose of in a sharps container
Storage of insulin
Your spare stock of insulin should be stored in a fridge. Do not put it too close to or in the freezer compartment, as this will damage the insulin if it freezes.
The insulin you are currently using should be kept at room temperature 25 degrees centigrade and thrown away if not used up within 28 days.
Be aware that during summer months room temperature may rise above this level.