Insulin is a hormone made by an organ in our bodies called the pancreas. The pancreas lies just behind the stomach. The function of insulin is to help our bodies use glucose for energy.

For all people with Type 1 diabetes and for some people with Type 2 diabetes, insulin is essential to keep blood glucose levels under control.

The three groups of insulin

There are three groups of insulin – animal, human (not from humans but produced synthetically to match human insulin) and analogues (if we think of the insulin molecule as being like a string of beads, scientists have managed to alter the position of some of these beads to create 'analogues' of insulin).

Nowadays, most people use human insulin and insulin analogues, although a small number of people still use animal insulin because they have some evidence that they otherwise lose their awareness of hypos or they find animal insulin works better for them.

The main types of insulin

There are six main types of insulin:

• Rapid-acting analogues can be injected just before, with or after food and have a peak action at between 0 and three hours. They tend to last between two and five hours and only last long enough for the meal at which they are taken. They are clear in appearance.
• Long-acting analogues tend to be injected once a day to provide background insulin lasting approximately 24 hours. They don't need to be taken with food because they don't have a peak action. They are clear in appearance.
• Short-acting insulins should be injected 15–30 minutes before a meal to cover the rise in blood glucose levels that occurs after eating. They have a peak action of two–six hours and can last for up to eight hours. They are clear in appearance.
• Medium- and long-acting insulins are taken once or twice a day to provide background insulin or in combination with short-acting insulins/rapid-acting analogues. Their peak activity is between four and 12 hours and can last up to 30 hours. They are cloudy in appearance.
• Mixed insulin – a combination of medium- and short-acting insulin.
• Mixed analogue – a combination of medium-acting insulin and rapid-acting analogue.

Manufacturers

There are four companies who make insulin: