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

If your pancreas doesn’t produce insulin at all or doesn’t make enough of it or if the insulin in your body doesn’t work as efficiently as it should, it can cause harmful and even life threatening complications.

The most common condition associated with insulin is diabetes.

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

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 to:

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

When you eat food, the carbohydrates that you consume get broken down into glucose.

Your pancreas then releases insulin so that the glucose in your blood can be transported to the cells in your body. Glucose will either be used as energy by those cells or stored in your liver as glycogen for when it’s needed later.

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 carry out all its essential functions.

If your pancreas doesn’t produce enough insulin or if the insulin in your body doesn’t work properly, blood sugar will remain in your bloodstream and not be moved 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.

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

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

  • Type 1 diabetes. With type 1 diabetes, the pancreas doesn’t make insulin or doesn’t make enough of it. People with type 1 diabetes need to take insulin by injection on a daily basis. Type 1 diabetes is considered an autoimmune condition and is more commonly diagnosed in children. About 5 to 10 percent of all people with diabetes have type 1 diabetes.
  • Type 2 diabetes. With type 2 diabetes, your pancreas may not make enough insulin or your body may not respond to it properly. In other words, the insulin in your body doesn’t work as well as it should. Type 2 diabetes is most often diagnosed in adults but it’s increasingly being seen in children and teenagers. It is very often associated with obesity and insulin resistance. About 90 to 95 percent of all people with diabetes have type 2 diabetes.

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

When insulin doesn’t work the way it should, it can cause a wide range of symptoms. These symptoms can be severe and develop very quickly in type 1 diabetes.

On the other hand, the symptoms come on a lot more slowly in type 2 diabetes. It can take years for symptoms to develop. Often, people are diagnosed with type 2 diabetes before they notice any symptoms.

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

Another common sign of insulin resistance and prediabetes or diabetes is acanthosis nigricans, which are velvety hyperpigmented plaques (thickened skin) commonly found on the neck or in the armpits. It is one of the earliest telltale signs of high glucose levels.

People with type 1 diabetes are generally diagnosed when symptoms cause them to seek medical care.

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 levels or an A1C test can indicate if your blood sugar is within a healthy range. This can signal whether the insulin in your body is working correctly.

Fasting blood sugar test

A fasting blood sugar test measures your blood sugar after not eating for at least 8 hours. This test is often done in the morning after you’ve gone without eating overnight. The following chart shows what the results of a fasting blood sugar test mean.

ResultFasting blood sugar level
standard range99 mg/dL or below
prediabetes100–125 mg/dL
diabetes100–125 mg/dL

A1C test

An A1c test measures your average blood sugar levels over the past 2 to 3 months. The following chart shows what the results of a A1C test mean.

ResultA1C level
standard rangebelow 5.7%
diabetes6.5% or above

About the 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 index diet)
  • increasing your physical activity
  • losing weight, if you have overweight
  • quitting smoking, if you smoke

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

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

You have to inject insulin into the fat under your skin for it to get to your bloodstream. You cannot take it as a pill because it would get broken down during the process of digestion, which would make it much less effective than it needs to be.

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

There are several different types of insulin. The types of insulin may seem overwhelming at first, especially if you haven’t taken insulin before. Your doctor will work with you to:

  • determine what type of insulin you need
  • figure out when you need it
  • explain how to administer it safely

Your doctor will take several factors into consideration to determine which type of insulin is right for you. For instance, they will look at:

  • your blood sugar levels
  • the length of time you’ve had diabetes
  • other medications you may be taking
  • your overall 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 include the following:

  • Rapid-acting insulin. Rapid-acting insulin affects blood glucose about 15 minutes after you take it. It peaks in 1 to 2 hours and continues to work for around 2 to 4 hours. Rapid-acting insulin products include:
    • aspart (Novolog, Fiasp)
    • glulisine (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 to 3 hours and works for about 3 to 6 hours. Regular or short-acting insulin products include:
    • Humeline 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 to 12 hours and is effective for around 12 to 18 hours. Intermediate-acting insulin products include:
    • Humeline N
    • Novolin N
    • ReliOn/Novolin N
  • Long-acting insulin. Long-acting insulin starts to work within 1 to 2 hours, but it doesn’t peak like other types of insulin. It has a lower intensity and can keep working 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 yourself with insulin.

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

  • Insulin pens. Insulin pens are prefilled containers that help ensure accurate dosing. You still need to poke yourself with a needle, but these devices make measuring and delivering insulin a lot easier.
  • Insulin pumps. Insulin pumps are small, portable, computerized devices that can deliver insulin before each meal and throughout the day. They’re attracted to a thin tube that’s implanted under your skin. Some insulin pumps are also able to measure your blood sugar.
  • Inhalable insulin. Inhalabale insulin may also be an option. However, this type of insulin is expensive and isn’t covered by most insurance plans.

Insulin is an important hormone that helps your body use, store, and regulate the glucose (sugar) in your blood. When the insulin in your body doesn’t work correctly, your blood sugar can build up to 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 insulin is sometimes needed.

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