What Does Insulin Do?

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Insulin Syringe Used for Diabetes

Do you take insulin? Or has your healthcare provider recommended that you start taking it? You probably have specific thoughts or feelings about this medicine. Many people view insulin as a lifesaver, while others are fearful. There are a lot of misconceptions surrounding this drug, too. For example, many people believe that having to take insulin will cause blindness or mean the loss of a limb or is a sign that their diabetes is worsening. While these beliefs are understandable, the reality is that they’re not true. In fact, insulin is a lifesaving medication — without it, people with type 1 diabetes wouldn’t be alive, and many people with type 2 diabetes would struggle to manage their diabetes.

Before the discovery of insulin, there was no treatment for type 1 diabetes. People who had type 1 diabetes were often put on starvation diets, but they did not live long. Two researchers, Frederick Banting and Charles Best, figured out how to extract and refine insulin from the pancreases of dogs and cattle in 1921; in 1922, the first injection was given to a dying 14-year-old boy with diabetes, saving his life. That same year, Eli Lilly became the first manufacturer to mass produce insulin. Its discovery was so groundbreaking and important that it’s often called one of the greatest medical developments of the 20th century.

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What is insulin?

Insulin is a hormone. Hormones are the body’s chemical messengers that affect many different processes, such as growth, metabolism, and reproduction. Insulin is made in the beta cells of the pancreas, and one of its main roles is to help regulate, or control, your blood sugar; more specifically, it prevents blood sugar levels 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.

In the absence of diabetes, the pancreas always releases a low level of insulin into the bloodstream help keep things in check (if you’re on an insulin pump, this is what your basal rate is doing). When food is eaten, the pancreas steps up to the plate and releases more insulin into the bloodstream. It, in turn, signals muscle, fat, and liver cells to take up 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.

Insulin is also known as a “storage” hormone, since when there’s more glucose than the body needs, it helps the body store that excess glucose in the liver to be used at a later time. It also tells the liver to stop releasing glucose into the bloodstream, and it helps to move amino acids (from protein digestion) and fatty acids (from fat digestion) into cells.

Type 1 diabetes

Type 1 diabetes is an autoimmune disorder that destroys the beta cells (the cells that make insulin) in the pancreas. This means that the body can’t produce insulin (or 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 not seem so bad, 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. If you have type 1 diabetes, you must take insulin — either by injection, pump, or with an inhaler — to survive. At this time, there is no other way to successfully manage type 1 diabetes.

Type 2 diabetes

When it comes to type 2 diabetes, things are different. 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 take up glucose from the bloodstream. As a result, the body needs higher levels of insulin to help fuel cells. The beta cells in the pancreas kick into overdrive to produce insulin in order to keep up with the increased demand. Levels of the hormone 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 bloodstream build up, and prediabetes or type 2 diabetes can set in.

Many people with type 2 diabetes can successfully manage their diabetes with a combination of lifestyle measures, including nutrition, physical activity, and weight loss, as well as medicines that aren’t insulin. These include pills and non-insulin injectables. But after a time, it’s thought that most people with type 2 diabetes will need to take insulin. That’s because type 2 diabetes progresses, and beta cells stop making enough insulin. No amount of diabetes pills will work if there is no insulin available.

Types of insulin

Insulin has come a long way since 1921. Today, there are many types available, characterized by how fast and how long it works in your body.

Insulin is differentiated by certain factors:

· Onset: how quickly it lowers your blood sugar

· Peak: when it is working its hardest

· Duration: how long it works to lower your blood sugar


Insulins that work quickly and that are typically taken before a meal are the fast-acting and short-acting insulins. Examples include Fiasp, Lyumjev, Humalog, Novolog, Apidra, and Regular insulin.


Next is intermediate-acting insulin, which is NPH. This is usually taken twice a day.

Long-acting and ultra-long-acting

Then, there are long-acting and ultra-long-acting insulins, which include Lantus, Basaglar, Levemir, Toujeo, and Tresiba. These are usually given once a day (sometimes twice) and their purpose is to keep blood sugars level overnight and between meals.


Premixed insulins, such as Humalog Mix 75/25 and Novolog Mix 70/30, are insulins that combine a fast- or short-acting insulin with an intermediate-acting insulin. They’re typically taken before breakfast and dinner.

If you have type 1 diabetes and administer insulin by injection, you’ll need to take two types of insulin: a fast- or short-acting insulin and an intermediate- or long-acting insulin. People with type 2 diabetes often start with a long-acting insulin first, and then eventually take a fast-or short-acting insulin.

If you use an insulin pump, you use only a fast- or short-acting insulin. That’s because the pump delivers a small basal rate of insulin 24 hours a day, and then you bolus a dose of insulin before you eat.

Sound confusing? That’s understandable. It certainly can be confusing to make sense of all of the different types of insulins and what is best for you to take. Your healthcare provider or a diabetes educator should go over the various options with you and discuss what is best for you. Keep in mind that your health insurance may have a say in what you take, too — they usually cover certain types of insulin, so always check with your health plan as to what they will pay for.

Is there an insulin “pill”?

Some people are scared of taking insulin because it has to be injected or infused (i.e., via a pump). Injections and pump infusion sets 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 also usually needed, and that must be taken by injection.)

Why isn’t there 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 more than 80 years. The problem is that insulin 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, it would have a tough time passing through the lining of the intestines into the bloodstream.

But don’t give up hope! Various drug companies are fast at work on creating an oral insulin. In fact, Oramed Pharmaceuticals recently announced that they have screened the first patients in its ORA-D-013-2 study, the second of two concurrent Phase 3 studies of its oral insulin capsule called ORMD-0801.

Insulin fears

There are various reasons that people are hesitant or even downright scared of going on insulin. Common concerns include:

· Fear of needles

· Fear that injections will hurt

· Fear of having low blood sugars

· Fear of gaining weight

· Fear of getting complications, like blindness or kidney damage

While it’s perfectly natural to be scared of these issues, realize that all of them can be addressed. Today’s insulin needles are thin and small and virtually painless. Low blood sugars can be prevented and easily treated if they do occur. Weight gain can be prevented. And taking insulin doesn’t cause complications (but having constant high blood sugars can).

What you shouldn’t be afraid of is discussing your fears or concerns with your diabetes care team. Make sure you get your questions answered and also make sure to be a part of the decision-making, too. You may just find that taking insulin improves the quality of your life in many ways!

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, DiabeticConnect.com, and CDiabetes.com.

Originally Published December 5, 2016

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