Diabetes is a medical condition that causes blood glucose (sugar) levels to rise higher than normal. This is also called hyperglycemia.

When you eat, your body breaks food down into glucose and sends it into the blood. Insulin then helps move the glucose from the blood into your cells. When glucose enters your cells, it is either used as fuel for energy right away or stored for later use. In people with diabetes, there is a problem with insulin, but not everyone with diabetes has the same problem.

There are different types of diabetes—type 1, type 2, and a condition called gestational diabetes, which happens during pregnancy. If you have diabetes, your body either doesn’t make enough insulin, can’t use the insulin it does make very well, or both.

In type 1 diabetes, your immune system mistakenly destroys the beta-cells in your pancreas that make insulin. Your body treats these cells as invaders and destroys them. This can happen over a few weeks, months, or years.

When enough beta-cells are destroyed, your pancreas makes little or no insulin. Because the pancreas does not make insulin, the insulin needs to be replaced. People with type 1 diabetes take insulin by injection with a syringe, an insulin pen, or an insulin pump. Insulin does not come in a pill. Without insulin, your blood glucose rises and is higher than normal, which is called hyperglycemia.

Type 1 diabetes affects about 5% of people with diabetes in the United States. In the past, type 1 diabetes was called juvenile diabetes or insulin-dependent diabetes. It’s usually first diagnosed in young people, but it can occur at any age. Type 1 diabetes is much less common than type 2 diabetes.

In type 2 diabetes, your body does not use insulin properly. This is called insulin resistance. At first, the beta-cells make extra insulin to make up for it. But, over time, your pancreas isn’t able to keep up and can’t make enough insulin to keep your blood glucose levels normal. Type 2 diabetes can be treated with oral medications and/or insulin. Type 1 diabetes is always treated with insulin.

Scientists aren’t sure what causes type 1 diabetes. It is not contagious, and it is not caused by eating sugar. Research is under way to find the exact causes of type 1 diabetes and how it might be prevented.


The two goals of diabetes treatment are to make sure you feel well on a day-to-day basis and to prevent or delay long-term health problems. The best way to reach those goals is by:

  • taking insulin

  • planning your meals—choosing what, how much, and when to eat

  • being physically active

Getting an A1C test at least twice a year helps you and your health care team keep track of how well you are controlling your blood glucose levels. A1C is part of your diabetes ABCs, which will tell you if your overall diabetes treatment is working. The ABCs of diabetes are:


Your A1C test tells you your average blood glucose for the past 2–3 months. It’s the blood check “with a memory.” Your health care provider may call this your estimated average glucose, or eAG. The eAG gives your A1C results in the same units (mg/dL) as the glucose meter you use at home.


Your blood pressure numbers tell you the force of blood inside your blood vessels. When your blood pressure is high, your heart has to work harder.


Your cholesterol numbers tell you about the amount of fat in your blood. Some kinds of cholesterol can raise your risk for heart attack and stroke.

Diabetes can affect how you feel each day. If your blood glucose level is too high or too low (hypoglycemia), you may not feel well. Keeping your blood glucose in a target range will help you feel your best.

People with type 1 diabetes must take insulin several times a day to keep their blood glucose under control. You also need to check your glucose level regularly and use the information to adjust the amount of insulin you are taking. Talk with your health care team about how and when to check your glucose.

While most of the day-to-day care of diabetes is up to you, your health care team is there to help you.

This handout was published in Clinical Diabetes, Vol. 39, issue 3, 2021, and was adapted from the American Diabetes Association’s Diabetes Advisor handout “Type 1 Diabetes.” Visit the Association’s Patient Education Library at professional.diabetes.org/PatientEd for hundreds of free, downloadable handouts in English and Spanish. Distribute these to your patients and share them with others on your health care team. Copyright American Diabetes Association, Inc., 2021.

Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered. More information is available at https://www.diabetesjournals.org/content/license.