Your body only needs to make one kind of insulin because it can control how much and when the insulin it makes should work. If you have diabetes and need to inject insulin, it can’t always work exactly like your pancreas should, but there are four different types of injectable insulin to help match it as closely as possible. What makes them different is the amount of time it takes to get to the bloodstream and start to lower blood sugar. This is called onset of action. The time the insulin is working hardest is called the peak time. And the whole amount of time that insulin works to lower blood sugar is called the duration of action.
4 Types of injectable insulin:
1) Fast-acting: This type is often used as a mealtime (or bolus) insulin, such as insulin lispro, insulin aspart and insulin glulisine.
2) Short-acting: Also known as regular insulin, this is another bolus or mealtime insulin. It takes a while longer to work than fast-acting insulin and lasts a little longer in your body.
3) Intermediate-acting: Also known as NPH, intermediate-acting insulin is insulin that lasts for a longer time than fast- or short-acting insulin. This insulin can act as a background (or basal) insulin for some people.
4) Long-acting: This is a background (or basal) insulin, such as insulin glargine (Lantus™) and insulin detemir (Levemir™.) This type of insulin lasts longer than intermediate-acting insulin.
Source: Canadian Diabetes Association (www.diabetes.ca)