Insulin Types

When insulin was first developed, animal sources of insulin were used, particularly bovine or porcine insulin (from cattle or pigs).  There were many complications of using these types of insulin, including allergies to animal insulin.  It was then when human insulin was described and was synthesized in the laboratory. In today’s time, the major insulin type used is human insulin, which has far fewer complications and fewer allergies.

Human insulin products and insulin analogs are used by the body to replace insulin not made by the pancreas.  They are divided into different types according to when they begin to act on the body, the peak onset of action, and the time when the insulin is finally gone from the body.

Insulin analogs have been manufactured because human insulin is not able to be used by everyone.  In the vials of insulin, high concentrations of the synthetic hormone often clump the insulin together, which results in a slow and unpredictable absorption of the hormone.  Insulin analogs are generally considered to be more reliable and have a more predictable effect on the body.  These fast acting insulin analogs work faster than regular insulin.  Long acting insulin analogs tend to last longer in the body and release steady streams of insulin, without much of a peak.

The animal (bovine and porcine) insulin has been used for the treatment of diabetes since 1925.  The insulin was made by extracting the insulin from the pancreases of cows and pigs.  This lasted until the early part of the 1980s, when there was an advancement in technology that allowed manufacturers to make human insulin in synthetic form.  Now synthetic human insulin is used by the vast majority of diabetics. In the future, insulin analogs will be the most common choice for diabetics who need glucose reduction.

Insulin Characteristics

Insulin has different characteristics.  The differences in the various types of insulin include the following:

• Each has a different onset of action and acts in the body more quickly or more slowly.
• Each has a different peak action, which is the maximal impact the insulin has on the body.
• Each has a different duration of action, which is the time at which the insulin eventually wears off.
• Each is of a different concentration. For example, in the US, the vials have a concentration of 100 units per milliliter, which is also referred to as U100. Other countries have insulin in different concentrations.
• Each has a different route of delivery. Some insulins are designed to be injectable into the fat under the skin, while other are designed to be used by IV.

Most of the time, insulin is of the injectable kind. It is injected underneath the skin into the fatty tissue of the abdomen, thighs, buttocks, or upper arm, where the fat concentrations beneath the skin are the highest.  Only in hospital settings is the intravenous form of insulin used.  There are also insulin pumps, which deliver insulin directly from a pump that has been implanted under the skin.

The Various Types of Insulin

Insulin can be divided into three main types:

• Fast acting
• Intermediate acting
• Long acting

Fast Acting Insulin

This is a type of insulin that is rapidly absorbed from the fatty tissue just beneath the skin.  The insulin quickly hits the bloodstream so that it can work to decrease blood sugar.  It is often used to keep the blood glucose levels in the bloodstream down during mealtime and when having a snack.

Rapid acting insulin analogs include Insulin Lyspro, Insulin Aspart, and Insulin Glulisine.  They each have an onset of action that is between 5 and 15 minutes.  They peak in about 5-6 hours and have a duration of action of about four to six hours.  The effects of the insulin analogs are similar to insulin; however, its onset, peak, and duration of action do not vary according to the dose. This is not the case with insulin, in which the usage parameters vary according to the amount of insulin given.

Regular Insulin usually starts to work within 30 minutes to one hour. The peak effect of this type of insulin is between 2 and 4 hours. The duration of action is between 6 and 8 hours.  The more insulin that is given, the faster is its onset of action but it has a longer peak effect and a longer duration of action.

Intermediate Acting Insulin

This is a type of insulin that is designed to absorb a little bit more slowly in the body and has a longer duration of action.  It is used to control the blood sugar during the nighttime hours, between meals, and when the individual is fasting.

NPH insulin has an onset of action that is about 1-2 hours.  The peak effect of this type of insulin is 4-6 hours, and it lasts in the system longer than 12 hours.  Tiny doses of NPH insulin will peak earlier and will have a shorter action in the body, while high doses of NPH insulin will take longer to peak and leave the body after a long period of time.

Premixed Insulin

This involves a mixture of NPH insulin with a rapid acting insulin analog or regular short acting insulin.  It has the benefit of acting quickly on the body with the NPH part of the mixture used as a longer acting insulin.  It is used by diabetics that cannot mix their own insulin from separate vials and by diabetics who find it more convenient to use a mixture over a single type of insulin.

Long Acting Insulin

This type of insulin is slowly absorbed by the body and does not have a very high peak.  Instead it acts as a stable plateau of insulin that acts throughout a 24-hour period of time.  It is often taken at bedtime, where it keeps blood sugar levels in check during the night.
There are long acting insulin analogs called Insulin Glargine or Insulin Detemir.  These analogs don’t begin to work until 1 ½ to 2 hours have passed.  These analogs plateau over several hours and then the action flattens out so that they last in the system for about 24 hours.

References:

1. Insulin A to Z: A Guide to Different Types of Insulin. http://www.joslin.org/info/insulin_a_to_z_a_guide_on_different_types_of_insulin.html.  Accessed 5/17/16.
2. Types of Insulin. http://dtc.ucsf.edu/types-of-diabetes/type2/treatment-of-type-2-diabetes/medications-and-therapies/type-2-insulin-rx/types-of-insulin/. Accessed 5/17/16.