Type 1 Diabetes

Reviewed by: HU Medical Review Board | Last reviewed: October 2020.

In people with type 1 diabetes, their body’s immune system attacks and destroys the cells in the pancreas that make insulin. This is a hormone that helps glucose (sugar) from the food you eat get into cells to be used for energy. Without insulin, glucose cannot get into cells and instead builds up in the blood. Over time, high blood glucose levels cause a number of serious health problems.1

Because a person with type 1 diabetes can not produce the insulin they need to properly use glucose, they must take insulin on a daily basis to keep their blood glucose levels in control and stay healthy.1,2

Type 1 diabetes is usually diagnosed in children and young adults, but it can develop at any age. About 1.6 million people in the United States have type 1 diabetes, including children and teens.2,3

What causes type 1 diabetes?

The exact cause of type 1 diabetes is not known. However, scientists and doctors have identified a number of factors that may play a role in causing the body’s immune system to attack cells in the pancreas. These factors include genetics (certain inherited genes that make a person more likely to develop a disease) and environmental factors, such as viruses.1,2

How is type 1 diabetes different from type 2 diabetes?

Both type 1 and type 2 diabetes are identified by high blood glucose levels. However, there are important differences between the 2 conditions:9,10


  • In type 1 diabetes, the body is no longer able to make insulin.
  • In type 2 diabetes, the body still makes insulin, but it does not make enough of it or does not use it well. Eventually, it stops making insulin altogether.

Age at diagnosis

  • Type 1 diabetes is often diagnosed in childhood or adolescence, but it can develop at any age.
  • Type 2 diabetes is usually diagnosed in people over 45, but it is seen in people of all ages. It is also increasingly common in children.

Risk factors

  • Family history and exposure to viruses and environmental factors are risk factors for type 1 diabetes.
  • Family history, being overweight and/or inactive, and high blood pressure are risk factors for type 2 diabetes.


  • There are no known prevention methods for type 1 diabetes.
  • A healthy lifestyle and weight can prevent type 2 diabetes.


  • People with type 1 diabetes require insulin every day to stay alive
  • Some people with type 2 diabetes can control their blood glucose levels with exercise and diet changes. Others are treated with medicine or insulin.

What are the symptoms of type 1 diabetes?

Some people with type 1 diabetes have very mild symptoms that go unnoticed. However, symptoms may also develop very quickly. Once they appear, symptoms can be severe and include:4

  • Blurred vision
  • Excessive thirst and increased urination
  • Constant hunger
  • Fatigue
  • Sores or cuts that heal slowly or do not heal
  • Sudden, unexplained weight loss

Early detection and treatment of type 1 diabetes is very important. Without treatment with insulin, a person with diabetes is at risk for diabetic ketoacidosis (DKA). This happens when the body breaks down fat too quickly. The liver then processes the fat into ketones, a type of chemical, and sends them into your blood. This causes your blood to become acidic. Symptoms of DKA, including confusion, fatigue, nausea/vomiting, and pain, can develop very quickly. In extreme cases, DKA can cause a person to go into a coma, so immediate medical attention is important. If you experience symptoms of ketoacidosis, call your doctor right away.5

DKA most commonly occurs in people who are sick with nausea, vomiting, and not eating. Therefore they do not take their insulin. It can also occur in people who do not know they have diabetes and their pancreas has already failed to produce the necessary amount of insulin. Illness also increases your need for insulin because your body responds by increasing blood sugar levels.6

How is type 1 diabetes diagnosed?

In most cases, testing for type 1 diabetes is done in people who have diabetes symptoms. However, if you have a family history of type 1 diabetes, your doctor will probably test you even if you do not have symptoms.7

There are a few different tests that can be used to diagnose diabetes. These tests measure your blood glucose level. They include:8

  • Fasting blood glucose test – a blood sugar level of 126 mg/dl or higher is considered diabetes
  • Hemoglobin A1C test – a level of 6.5 percent or higher is considered diabetes
  • Random blood glucose test – a blood glucose level of 200 mg/dL or higher is considered diabetes

If your blood glucose level indicates diabetes, your doctor may also test your blood for antibodies that are common in type 1 diabetes.8

How is type 1 diabetes treated?

It is important to follow a treatment plan to keep blood glucose levels within a healthy range. To do that, people with type 1 diabetes need to:2

  • Regularly measure blood glucose levels
  • Take insulin as prescribed
  • Eat a healthy diet
  • Get regular physical activity

There is no cure for type 1 diabetes, so people with the condition need treatment for the rest of their lives. Your doctor and care team can help you create and stick to a treatment plan that helps you feel healthy and avoid complications caused by diabetes.2

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