Everything You Didn’t Know You Didn’t Know About Insulin

What is insulin exactly?

We’ve all heard of insulin, and most of us know that insulin is a necessary part of the human body. Most people’s pancreases make insulin, which cells are then able to use to help them store energy from food. If our bodies don’t make insulin (type 1 diabetes), we have to get some from outside sources. If our bodies don’t know how to use insulin properly (type 2 diabetes), we have to make lifestyle changes or take medications to help our bodies learn to utilize it properly, or we may have to inject insulin into our bodies.

But how much more than that do you know? Do you know what types of insulin are out there? Do you understand why your doctor recommended a certain type of insulin for you? If not, we’re here to help.

Endogenous versus exogenous

This is probably the simplest way to categorize types of insulin. Endogenous insulin is the type that most human pancreases are able to make naturally. Exogenous insulin is insulin that is injected into the body or used with a pump. This type of insulin is either from an animal source or man-made in a laboratory.

medically accurate illustration of the pancreas

Basal versus bolus

In a person without diabetes, the pancreas is always secreting a basic low level of insulin for the cells in the body to use. This basic insulin level is known as “basal insulin.” When you eat, your body requires an extra dose of insulin to help it store the energy from your food, and the pancreas secretes more insulin in response. That extra dose is called a “bolus.”

If you get insulin from an outside source instead of from your pancreas, the longer-acting insulins work more similarly to your body’s natural basal insulin, and shorter-acting insulins work more similarly to your body’s natural bolus. If you take a longer-acting insulin, you likely take it at the same one or two times per day to keep your basal insulin at the right level. If you take shorter-acting insulins, you probably take them around the time you eat as a bolus to offset the spike in your blood sugar caused by the meal.

Learn more about the difference between basal and bolus here.

Animal, human, or analogue?

This is a particularly difficult part of the lesson, but here’s the gist of it. All three of these types of insulin are exogenous insulins, meaning they are not made by the human pancreas. Animal insulins are—you guessed it—made in the pancreases of animals and extracted for human use. Human insulins, on the other hand, are man-made in a laboratory, not in a pancreas. And analogue insulins are natural insulins that are modified by humans; they are engineered to work at different speeds to meet the lifestyle needs of all kinds of people with diabetes.

Learn more about animal, human, and analogue insulins here.


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Insulins by speed and duration

If you have diabetes and treat your condition with insulin, chances are you know how fast and how long your insulin works, because that helps you determine when to take it.

Fast-acting insulin starts to work just 15 minutes after it’s been administered. It peaks in about an hour and continues to work for a few more hours.

Short-acting insulin starts working about half an hour after injection and peaks at about 2 or 3 hours, after which it works for 3 to 6 more hours.

Intermediate-acting insulin takes about 2 to 4 hours to start working, peaks 4-12 hours after that, and continues to work for 12 to 18 hours longer. It is usually administered twice a day.

Long-lasting insulin takes several hours to start working and keeps working for about 24 hours.

Some people with diabetes also take a pre-mixed insulin, which includes two insulins with different speeds. The type (or types) of insulin you’ll need depends on your diet and exercise patterns, as well as other aspects of your lifestyle.

What does all this mean for me?

You should always talk to your doctor before choosing the insulin you believe is right for you, but we hope the information in this article helps you better understand your doctor’s suggestions. In the end, it is your body and your diabetes, and you should know all the facts so that you can make informed decisions—and understand exactly what you’ve decided on.

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