Insulin is a hormone produced by the pancreas that has 3 important functions. Insulin allows glucose to pass into cells to be used for energy, it reduces the production of glucose by the liver and muscles, and it suppresses the breakdown of fat as an energy source. When there is not enough insulin produced, such as happens in type 1 diabetes, or when the body cannot properly use the insulin it produces, as in type 2 diabetes, blood glucose levels rise because glucose does not enter the cells where it can be used for energy. Cells signal the that they are “hungry” because of the lack of energy, causing the liver to release glycogen, the storage form of glucose, which further increases blood glucose levels. When blood glucose exceeds about 180 mg/dl, glucose is spilled into the urine. Large amounts of water are excreted by the kidneys to dissolve this sugar causing frequent urination and thirst.

Insulin is used to allow glucose to enter the cells where it can be used for energy. Insulin must be injected because it is a protein which is broken down by digestive enzymes if taken orally. Beef, pork and human insulin have been used to treat diabetes. Beef insulin has been discontinued in the US. Virtually all diabetics now placed on insulin therapy use human insulin. There are different types of insulin available that are differentiated by the time they take to begin to work (onset), the time until their peak activity is reached, and how long the effect lasts (duration).

The original short-acting insulin was known as regular insulin. It takes 30 minutes to onset, reaches its peak in 2 to 4 hours and has a duration of effect of 4 to 8 hours. Other rapid-acting insulins include Novolog, Humalog, and Apidra. These have an onset of 10 to 15 minutes, reach their peak in 30 to 60 minutes, and only last for 4 hours. NPH insulins are intermediate-acting. They have an onset of 2 to 4 hours, peak in 6 to 8 hours and last for 12 to 15 hours. Recently introduced long-acting insulins include Lantus and Levimir. Lantus has an onset of between 4 and 6 hours. Because it has the same effect over 24 hours, it does not have a peak time of activity. Levimir has a shorter time to onset of 1 to 2 hours. Its effects are much more affected by the dose. Depending upon the dose, its peak varies from 2 to 12 hours. It also has an effect over 24 hours. Because of this long duration, Lantus and Levemir are referred to as basal insulins indicating that they provide a baseline effect all day. NPH insulin is mixed with regular, Novolog and Humalog insulins to provide a combination rapid action and longer duration. Exubera is a new orally inhaled short-acting insulin. Exubera has an onset in 10 to 20 minutes, it peaks in 2 hours and has a duration of about 6 hours.

Your diabetes care practitioner will work with you to determine the best insulin for your condition and lifestyle. With multiple choices in short, intermediate, and long-acting insulins and combinations available, you can select the insulin that will help you best control your blood glucose levels and reduce your risk of complications from diabetes.

Reference: http://www.diabetes123.com/d_0n_110.htm.

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