Insulin Basics

Insulin is a hormone in the body which plays a crucial role in helping to regulate levels of blood glucose and provide the body with the energy it needs to function.

Insulin has been used as a medication for diabetes since the early 1920s, largely for the treatment of type 1 diabetes but also for some people with type 2 diabetes who are unable to produce enough natural insulin.

How does insulin work?

Insulin plays a number of key roles, one of which is allowing glucose in the blood to pass into body cells, such as muscles, to be used as fuel.

If no insulin is available in the body, that person will develop steadily higher blood sugar levels (hyperglycemia) and will become weaker and more tired until they receive an external supply of the hormone.

How is insulin taken?

Insulin is most commonly taken by injection but taking insulin with an insulin pump is becoming increasingly common for people with type 1 diabetes.

Insulin injections are usually delivered using an insulin pen, a device which allows very short and slim needles to be used.

Insulin pumps are devices that are attached to the body and continuously deliver doses of insulin throughout the day. Modern insulin pumps are small and can be worn and operated discreetly.

Types of insulin

There a number of different types of insulin available:

  • Analogue insulin – a synthetic insulin chemically altered to affect how quickly it is absorbed
  • Human insulin – a synthetic insulin designed to be a close replica of insulin in humans
  • Animal insulin – insulin that has been cultivated from the pancreases of animals

Insulin speeds

The following are the different types of insulin that act at different speeds – or in other words, how quickly the insulin is absorbed by the body:

  • Rapid acting insulin – peak activity between 15 mins and 2 hours of injecting
  • Short acting insulin – peak activity between 30 mins and 3 hours of injecting
  • Intermediate insulin – peak activity between 2 and 12 hours of injecting
  • Long acting insulin – insulin continually absorbed between 15 mins and up to 18 or 24 hours

Please note that these speeds are intended as a guide only and may not apply for all insulin types.

Some people, particularly those with type 1 diabetes, will take 2 different speeds of insulin each day. For example, some patients may take one or more injections of long acting insulin and a number of injections of short or rapid acting insulin.

Insulin regimens

Some people with diabetes will inject more often than other people with diabetes. How many times you inject per day will depend on your type of diabetes and the flexibility you require.

Insulin pump therapy, whereby insulin can be taken at the press of a few buttons, is also included as an insulin regimen.

The following insulin regimens are possible:

  • Once daily: Suitable for some people with type 2 diabetes
  • Twice daily: Typically involves two injections of short and intermediate insulin mixed together
  • Multiple daily injections: Typically involves taking at least 4 injections a day
  • Insulin pump therapy: Insulin delivery via insulin pump


Hypoglycemia (lower than normal blood sugar levels) is the most common side effect of taking insulin and one that can be dangerous if not spotted and treated quickly.

If you are put onto insulin, your diabetes care team should go through how to recognise the signs of hypoglycemia, how to treat it and how to prevent it occurring.