What Is Insulin?

The insulin your body makes naturally is a hormone. Insulin helps move sugar from the blood into the body’s cells, where it can be used for energy.

In people without diabetes, the pancreas releases insulin throughout the day. The pancreas is an organ that sits near the stomach. Special cells in the pancreas, called beta cells, make insulin. In between meals, the pancreas releases a low level of insulin to help the body have enough energy.

When you eat, your blood sugar (also known as blood glucose) rises. In people without diabetes, the pancreas releases more insulin when you eat to take sugar from the food you eat that is in your blood and bring it to the cells to be used as energy. This brings the blood sugar in the blood back down.

Insulin works like a key, unlocking cells to help deliver sugar from the blood. Every cell in the body has a lock on its cell wall, called a receptor. Insulin fits into that lock like a key, allowing sugar to enter the cells.

When the body is not able to make enough insulin, blood sugar is locked out of the cells, causing it to stay in the bloodstream. This leads to blood sugar building up until the levels are too high, which is also called hyperglycemia. This extra sugar in the blood that isn't reaching the cells is what makes people feel the symptoms of diabetes, such as often feeling tired or thirsty.

In the case of diabetes, when the body is either not making enough insulin, or cannot use it properly, insulin therapy is often used to replace what the body no longer produces naturally.

Types of modern insulin therapy

  • From the 1920s to the 1980s, insulin from animals was used for treatment
  • In the 1980s, the first generation of man-made insulin, called "human insulin”, was created. This man-made insulin was genetically identical to the body’s naturally produced insulin
  • By the late 1990s, insulin analogs were developed. Insulin analogs are almost similar to regular human insulin, but they are changed slightly to allow them to act more quickly or slowly than regular human insulin
  • Today, premix insulin analogs like NovoLog® Mix 70/30 combine the effects of fast-acting and long-acting insulin into 1 medication

Insulin analogs are a more recent type of insulin than human insulin. They have been changed slightly to allow fast-acting insulin to act more quickly or long-acting insulin to act more slowly and longer than human insulin.

Different types of insulin analogs are available. Each one has a specific:

Onset of action (when it starts to work)

Time of peak action (when its effect on blood sugar is greatest)

Duration of action (how long it works)

Long-acting insulin (also known as basal). This type works more slowly. It works longer to control blood sugar between meals and when you sleep. Long-acting insulin is taken either once or twice a day at the same time every day, often with your evening meal or at bedtime to help give up to 24-hour insulin coverage. This is often the first insulin prescribed by your doctor for type 2 diabetes.

Fast-acting insulin (also known as bolus or rapid-acting). This type is taken shortly before mealtime. It works quickly to control the rapid rise in blood sugar after meals. Fast-acting insulin mimics the body's natural release of insulin at mealtime.

Premix insulin. For appropriate people with diabetes, premix insulin combines the action of a fast-acting and long-acting insulin.

These types of insulin may help keep diabetes under control. But no one type is right for everyone. Each person's insulin need is different. And each person's insulin need may change over time.

Insulin analogs are preferred by the American Association of Clinical Endocrinologists and the American Diabetes Association. Your doctor and diabetes care team will prescribe the insulin that is best for you.

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Type 2 Diabetes and Insulin

Learn more about type 2 diabetes and the role insulin plays in your body with this helpful fact sheet from Cornerstones4Care®.

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