What is insulin?

Metabolism is the process by which glucose, consumed as food, is turned into energy that is useful for the body. In a normally functioning metabolic system, the ingestion of food signals the pancreas to release insulin into the bloodstream. This insulin, in turn, signals liver, muscle, and fat cells to take up glucose from the bloodstream. The glucose is metabolized to provide the body with the energy it needs. 
Intermountain Healthcare
Insulin is used to treat diabetes. It's taken by injection (shot) or with an insulin pump. As with other diabetes medications, it works best when you're following the rest of your treatment plan. This means checking your blood glucose regularly, following your meal plan, and exercising every day.

In general, insulin works just like the insulin made in a normal pancreas: It helps move glucose (sugar) out of your bloodstream and into your body's cells.

There are many types of insulin. Some work right away and don't last very long. Others act more slowly, over a longer period of time. Your doctor will explain which type you use and how to take it properly.
John A. Chabot
Endocrinology Diabetes & Metabolism

Insulin is a hormone that induces cells to take up glucose from the blood. When insulin is not present, cells are unable to take up glucose and use fat as an alternate energy source. An inability to produce insulin is the primary cause of type I diabetes mellitus.

Insulin is a hormone produced by beta cells in the pancreas. It breaks down sugar in the bloodstream so that the body can use glucose for fuel. In type 1 diabetes, the body has destroyed its own insulin-producing cells and insulin injections are needed to balance blood glucose levels. In type 2 diabetes, people become resistant to their own insulin and insulin injections may be needed to maintain normal blood sugar levels. Without adequate insulin, blood sugar builds up and can become dangerously high. Insulin lowers blood sugar in those who have diabetes. There are several different types of insulin.

Dr. Jack Merendino, MD
Endocrinology Diabetes & Metabolism
Insulin is a hormone that is produced by cells in your pancreas and is essential for maintaining proper health. (A hormone is a chemical that is manufactured in one part of the body and travels through the bloodstream to other parts of the body, where it has powerful effects.) One of insulin’s main jobs is to help transport glucose into your cells. Without insulin, you’d starve to death, because no matter how much you eat, if glucose and the energy it provides can’t get into your cells, you can’t survive.
The Best Life Guide to Managing Diabetes and Pre-Diabetes

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The Best Life Guide to Managing Diabetes and Pre-Diabetes

Bob Greene has helped millions of Americans become fit and healthy with his life-changing Best Life plan. Now, for the first time, Oprah's trusted expert on diet and fitness teams up with a leading...
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Nutrition & Dietetics
Insulin is a hormone produced by the pancreas. Its primary role is to make the body’s cells take in proteins, fatty acids, and glucose, the energy our bodies need that comes from the foods we eat. Whenever a person who does not have diabetes ingests food, his or her blood-glucose level rises. This causes the pancreas to release more insulin, which goes to the liver, ordering it to make less glucose. The insulin also instructs the muscles and fat cells to absorb more glucose, allowing nutrients to enter and feed the body’s cells. If this same person fasts, such as between meals or during sleep, the body’s insulin levels drop, causing the liver to make more glucose to provide energy until the next meal. In a person with diabetes, this process doesn’t work properly and the blood-glucose level continues to rise.
Insulin is a hormone. Hormones are chemical signals made by the body that tell various parts of the body how to do their jobs. Some hormones control how the cells in the body grow. Some control how the body uses food and energy to live. And other hormones help muscles to contract, blood to clot, or the heart to beat.
Dr. Mehmet Oz, MD
Cardiology (Cardiovascular Disease)
Insulin is a hormone normally produced by the pancreas that helps your body use sugar for energy. Watch the animation to learn more about insulin.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.