Mechanism of action of insulin: how does it work?

Your body produces a wide range of hormones to help control many important functions. Insulin is one of these vital hormones and is produced by your pancreas. It regulates how your body uses glucose, a form of sugar that is created when your body breaks down the carbohydrates you eat.

If your pancreas does not produce insulin at all or does not produce enough of it, or if the insulin in your body does not work as efficiently as it should, it can lead to harmful or even life-threatening complications.

The most common condition associated with insulin is diabetes.

This article will help you explain how insulin works, what happens when it stops working, and treatment options.

Insulin is a hormone produced by your pancreas that helps control how your body processes, stores, and uses glucose and other important nutrients.

Insulin is needed for:

  • regulate the amount of glucose in your bloodstream
  • help store glucose in your liver
  • controlling how your body metabolizes carbohydrates, proteins, and fats

When you eat food, the carbohydrates you consume break down into glucose.

Your pancreas then releases insulin so that the glucose in your blood can be transported to the cells of your body. The glucose will either be used as energy by these cells or stored in your liver as glycogen for later needs.

When insulin works this way, it helps keep your blood sugar levels within a healthy range and ensures your body gets the energy it needs to perform all of its essential functions.

If your pancreas isn’t producing enough insulin or if your body’s insulin isn’t working properly, blood sugar will stay in your bloodstream and won’t be transferred to your cells or to your liver for storage.

The two most common conditions associated with insulin are type 1 diabetes and type 2 diabetes.

On 34 million American adults had diagnosed or undiagnosed diabetes in 2020, more than double the number of American adults with diabetes 20 years ago.

Although both types of diabetes are associated with insulin-related complications, there are key differences between the two:

  • Type 1 diabetes. With type 1 diabetes, the pancreas does not make insulin or does not make enough of it. People with type 1 diabetes must take insulin by injection daily. Type 1 diabetes is considered an autoimmune disease and is more often diagnosed in children. On 5 to 10 percent of all people with diabetes have type 1 diabetes.
  • Type 2 diabetes. With type 2 diabetes, your pancreas may not produce enough insulin or your body may not respond to it properly. In other words, the insulin in your body isn’t working as well as it should. Type 2 diabetes is most commonly diagnosed in adults, but is increasingly seen in children and adolescents. It is very often associated with obesity and insulin resistance. On 90 to 95 percent of all people with diabetes have type 2 diabetes.

High blood sugar can damage organs and tissues throughout your body. The higher your blood sugar, and the higher levels of it you have, the greater your risk for many types of health complications, such as:

When insulin isn’t working as it should, it can cause a wide range of symptoms. These symptoms can be severe and develop very quickly into type 1 diabetes.

In contrast, symptoms appear much more slowly in type 2 diabetes. It can take years for symptoms to develop. Often people are diagnosed with type 2 diabetes before noticing any symptoms.

When symptoms are present in type 1 or type 2 diabetes, they may include:

Another common sign of insulin resistance and prediabetes or diabetes is acanthosis nigricans, which are hyperpigmented, velvety patches (thickened skin) commonly found on the neck or in the armpits. This is one of the first telltale signs of high blood sugar.

People with type 1 diabetes are usually diagnosed when symptoms cause them to see a doctor.

Type 2 diabetes is often diagnosed with a simple blood test during a routine physical exam or annual checkup.

A lab test of your fasting blood sugar or an A1C test can tell if your blood sugar is in a healthy range. This can tell if the insulin in your body is working properly.

Fasting blood glucose test

A fasting blood glucose test measures your blood sugar after you haven’t eaten for at least 8 hours. This test is often done in the morning after you have gone without food overnight. The following table shows what results a fasting blood glucose test average.

A1C test

An A1c test measures your average blood sugar over the past 2-3 months. The following table shows what results of an A1C test average.

About blood test results

If your test results indicate that you have prediabetes, your doctor will likely recommend lifestyle changes, such as:

  • eating a balanced, nutritious diet (often a low-glycemic diet)
  • increase your physical activity
  • lose weight, if you are overweight
  • quit smoking, if you smoke

These types of changes can help your body use insulin more efficiently and prevent prediabetes from progressing to diabetes.

People with type 1 diabetes should always take insulin, and they should also check their blood sugar throughout the day to make sure it stays within a target range.

You need to inject insulin into the fat under your skin for it to reach your bloodstream. You cannot take it in pill form because it will break down during the digestion process, making it much less effective than it should be.

People with type 2 diabetes who can manage their condition with lifestyle changes and other medications might not need to use insulin. People with type 2 diabetes will only be prescribed insulin if lifestyle changes and oral medications are not enough to keep blood sugar levels within a target range.

There are several types of insulin. Types of insulin can seem overwhelming at first, especially if you’ve never taken one before. Your doctor will work with you to:

  • determine the type of insulin you need
  • know when you need it
  • explain how to administer it safely

Your doctor will consider several factors to determine which type of insulin is right for you. For example, they will consider:

  • your blood sugar
  • the duration of your diabetes
  • other medicines you are taking
  • your general health and lifestyle
  • the type of health insurance you have

Depending on these factors, your doctor may prescribe one type of insulin or several types.

The main types of insulin are:

  • Rapid-acting insulin. Rapid-acting insulin affects blood sugar about 15 minutes after you take it. It peaks in 1-2 hours and continues to work for about 2-4 hours. Rapid-acting insulin products include:
    • aspart (Novolog, Fiasp)
    • glulisin (Apidra)
    • lispro (Humalog, Admelog)
  • Regular or short-acting insulin. Short-acting insulin reaches your bloodstream about 30 minutes after you inject it. It peaks in about 2-3 hours and works for about 3-6 hours. Regular or short-acting insulins include:
    • Humelin R
    • Novolin R
    • ReliOn/Humulin R
    • Velosulin BR
  • Intermediate-acting insulin. This type of insulin reaches your bloodstream about 2 to 4 hours after you inject it. It peaks in about 4-12 hours and is effective for about 12-18 hours. Intermediate-acting insulin products include:
    • Humeline N.
    • Novolin N
    • ReliOn/Novolin N
  • Long-acting insulin. Long-acting insulin starts working in 1-2 hours, but it doesn’t peak like other types of insulin. It has a lower intensity and can continue to work in your body for up to 24 hours. Long-acting insulin products include:
    • detemir (Levemir)
    • degludec (Tresiba)
    • glargine (Basaglar, Lantus, Toujeo)

Some manufacturers also sell premixed insulin that combines rapid- or short-acting insulin with intermediate-acting insulin.

Your healthcare professional will help you choose the right size syringe and can teach you how and when to inject insulin.

Syringes aren’t the only option for getting insulin into your bloodstream. If syringes are not suitable for you, you can also administer insulin using the following:

  • Insulin pens. Insulin pens are pre-filled containers that help ensure accurate dosing. You still have to prick yourself with a needle, but these devices make it much easier to measure and deliver insulin.
  • Insulin pumps. Insulin pumps are small, portable, computerized devices that can deliver insulin before each meal and throughout the day. They are attracted to a thin tube implanted under your skin. Some insulin pumps are also able to measure your blood sugar.
  • Inhalable insulin. Inhalable insulin may also be an option. However, this type of insulin is expensive and not covered by most insurance plans.

Insulin is an important hormone that helps your body use, store, and regulate glucose (sugar) in your blood. When the insulin in your body isn’t working properly, your blood sugar can reach dangerously high levels in your bloodstream.

The most common condition associated with insulin is diabetes. People with type 1 diabetes need to take insulin every day. Lifestyle changes and oral medications can manage type 2 diabetes, but sometimes insulin is needed.

There are several types of insulin. Some start working quickly and last a few hours. Others take longer to start working, but can last up to 24 hours. Your doctor will consider several factors to determine which type of insulin is right for you.

Maria D. Ervin