What Is Diabetes?

Diabetes is a disease that occurs when your blood glucose, also called blood sugar, is too high. Glucose is your body’s main source of energy. Your body can make glucose, but glucose also comes from the food you eat.

Insulin is a hormone made by the pancreas that helps glucose get into your cells to be used for energy. If you have diabetes, your body doesn’t make enough—or any—insulin, or doesn’t use insulin properly. Glucose then stays in your blood and doesn’t reach your cells.

Diabetes raises the risk for damage to the eyes, kidneys, nerves, and heart. Diabetes is also linked to some types of cancer. Taking steps to prevent or manage diabetes may lower your risk of developing diabetes health problems.

On the left, a diagram of a blood vessel that has a normal blood glucose level and contains fewer glucose molecules. On the right, a diagram of a blood vessel that has a high blood glucose level and contains more glucose molecules.Diabetes is a disease that occurs when your blood glucose, also called blood sugar, is too high.

What are the different types of diabetes?

The most common types of diabetes are type 1, type 2, and gestational diabetes.

Type 1 diabetes

If you have type 1 diabetes, your body makes little or no insulin. Your immune system attacks and destroys the cells in your pancreas that make insulin. Type 1 diabetes is usually diagnosed in children and young adults, although it can appear at any age. People with type 1 diabetes need to take insulin every day to stay alive.

Type 2 diabetes

If you have type 2 diabetes, the cells in your body don’t use insulin properly. The pancreas may be making insulin but is not making enough insulin to keep your blood glucose level in the normal range. Type 2 diabetes is the most common type of diabetes. You are more likely to develop type 2 diabetes if you have risk factors, such as overweight or obesity, and a family history of the disease. You can develop type 2 diabetes at any age, even during childhood.

You can help delay or prevent type 2 diabetes by knowing the risk factors and taking steps toward a healthier lifestyle, such as losing weight or preventing weight gain.

Gestational diabetes

Gestational diabetes is a type of diabetes that develops during pregnancy. Most of the time, this type of diabetes goes away after the baby is born. However, if you’ve had gestational diabetes, you have a higher chance of developing type 2 diabetes later in life. Sometimes diabetes diagnosed during pregnancy is type 2 diabetes.


People with prediabetes have blood glucose levels that are higher than normal but not high enough to be diagnosed with type 2 diabetes. If you have prediabetes, you have a higher risk of developing type 2 diabetes in the future. You also have a higher risk for heart disease than people with normal glucose levels.

Other types of diabetes

A less common type of diabetes, called monogenic diabetes, is caused by a change in a single gene. Diabetes can also come from having surgery to remove the pancreas, or from damage to the pancreas due to conditions such as cystic fibrosis or pancreatitis.

How common are diabetes and prediabetes?

More than 133 million Americans have diabetes or prediabetes.1

As of 2019, 37.3 million people—or 11.3% of the U.S. population—had diabetes.1 More than 1 in 4 people over the age of 65 had diabetes. Nearly 1 in 4 adults with diabetes didn’t know they had the disease.2

About 90% to 95% of diabetes cases are type 2 diabetes.3

In 2019, 96 million adults—38% of U.S. adults—had prediabetes.4

What other health problems can people with diabetes develop?

Over time, high blood glucose can damage your heart, kidneys, feet, and eyes. If you have diabetes, you can take steps to lower your chances of developing diabetes health problems by taking steps to improve your health and learning how to manage the disease. Managing your blood glucose, blood pressure, and cholesterol levels can help prevent future health problems.

Doctor using a special device to check the inside of a patient’s eye.Managing your blood glucose levels can help prevent future health problems, such as damage to your eyes.


Last Reviewed April 2023
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This content is provided as a service of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), part of the National Institutes of Health. NIDDK translates and disseminates research findings to increase knowledge and understanding about health and disease among patients, health professionals, and the public. Content produced by NIDDK is carefully reviewed by NIDDK scientists and other experts.

NIDDK would like to thank:
Daniel Bessesen, M.D., University of Colorado; Domenico Accili, M.D., Columbia University