What Does Insulin Do?

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Insulin Syringe Used for Diabetes

The word “insulin” can instill fear in many people who have or who are at risk for diabetes. Some of the beliefs around insulin are that if you have to take it, you’ll go blind or lose a limb. Or that insulin causes you to gain weight. Or that it means your diabetes is worsening. While these beliefs are understandable, the reality is that they’re not true. In fact, insulin is a life-saving medication: without it, people with type 1 diabetes wouldn’t be alive, and many people with type 2 diabetes would be struggling. The discovery of insulin is so important that it’s often called one of the greatest medical developments of the 20th century. This week, let’s delve into insulin and learn more about how truly amazing it is!

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What exactly is insulin?

Insulin is a hormone. It’s made in the beta cells of the pancreas, and one of its main roles is to help regulate, or control, your blood sugar. When there’s enough insulin in the body, it helps to keep your blood sugar from going too high. In people who don’t have diabetes, blood sugars are very carefully and tightly controlled, staying within a safe and healthy range.

After a person without diabetes eats a meal or a snack, the pancreas releases insulin. The insulin then signals muscle, fat and liver cells in the body to absorb glucose (sugar) from the bloodstream to be used for energy. In this sense, insulin is like a key that unlocks the doors of the cells to allow glucose to enter. You can also think of insulin as a “storage” hormone, since when there’s more glucose than the body needs, insulin helps the body store that excess glucose in the liver to be used at a later time. Insulin also signals the liver to stop releasing glucose into the bloodstream.


Insulin also helps shuttle amino acids (from protein digestion) and fatty acids (from fat digestion) into cells.

What happens to insulin in type 1 and type 2 diabetes?

Type 1 diabetes: what does insulin do

If you have type 1 diabetes, you must take insulin, either by injection or by insulin pump, to survive. Why? Type 1 diabetes is an autoimmune disease that destroys the beta cells in the pancreas. This means that the body can’t produce insulin (or at least enough of it). When this happens, the body literally can’t fuel itself, and it will start to use protein and fat stores for energy. This may seem OK, but blood sugar levels climb dangerously high. In addition, a serious condition called diabetic ketoacidosis (DKA) can set in, which, if not treated, can be fatal. Hopefully you can see why insulin is literally a life-saving medicine for those with type 1 diabetes.

Type 2 diabetes: what does insulin do

The situation with insulin in type 2 diabetes is very different from that in type 1. Type 2 diabetes is a condition of insulin resistance, meaning that muscle, fat and liver cells do not respond properly to insulin, and they can’t easily absorb glucose from the bloodstream. As a result, the body needs higher levels of insulin to help glucose enter cells. Those beta cells in the pancreas start to work overtime to keep up with the increased demand for insulin by making more and more. Insulin levels in the bloodstream may be high. But eventually, the beta cells exhaust themselves and can no longer keep up with the body’s demand. Glucose levels in the bloodsteam build up, and prediabetes or type 2 diabetes can set in.

Is there an insulin “pill”?

Some people are scared of taking insulin because it has to be injected or infused. Injections and infusions mean needles, and if you have a fear of them, it’s understandable that you’re not going to be too keen on insulin injections. (There is an inhalable insulin available, but that’s an ultra-rapid-acting insulin; a longer-acting insulin is usually needed, and that must be taken by injection.)

You might be wondering why scientists haven’t come up with an insulin pill. It would be so easy to swallow insulin in a pill or capsule form, wouldn’t it? Unfortunately, at this time, no oral form is available. But it’s not for lack of trying: Researchers have been working on this for at least 80 years. The problem is that insulin, as mentioned, is a hormone, and most hormones are types of proteins. The digestive tract breaks down proteins, and insulin is no exception. Insulin in a pill form wouldn’t make it through the digestive tract to do its job of regulating blood sugars. In addition, insulin would have a tough time passing through the lining of the intestines into the bloodstream. But let’s not give up hope: Various drug companies are busy plugging away at this issue in hopes of coming up with an oral insulin that would do away with injections.

Next week, we’ll take a closer look at how insulin is injected, as well as the many different types of insulin that are available.

Want to learn more about insulin? Read “Insulin” What You Need to Know” and “Insulin Basics.”

Amy CampbellAmy Campbell, MS, RD, LDN, CDE

A Registered Dietitian and Certified Diabetes Educator at Good Measures, LLC, where she is a CDE manager for a virtual diabetes program. Campbell is the author of Staying Healthy with Diabetes: Nutrition & Meal Planning, a co-author of 16 Myths of a Diabetic Diet, and has written for  publications including Diabetes Self-Management, Diabetes Spectrum, Clinical Diabetes, the Diabetes Research & Wellness Foundation’s newsletter,, and


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