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.
There are six main types of insulin:
• Rapid acting analogue - can be injected just before, with or after food and have a peak action at between 0 and 3 hours. It tends to last between 2 and 5 hours and only lasts long enough for the meal at which they are taken. It is clear in appearance.
• Long acting analogue - tends 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 insulin - should be injected 15-30 minutes before a meal to cover the rise in blood glucose levels that occurs after injecting. It has a peak action of 2-6 hours and can last for up to 8 hours. They are clear in appearance.
• Medium and long acting insulin - they 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 4 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.