In type 1 diabetes, the body can't make insulin, or it makes very little insulin. Insulin is needed to help sugar (glucose) enter cells for energy. Without insulin, glucose builds up in the blood. This causes high blood glucose or high blood sugar. In the past, type 1 diabetes was also called:

• Insulin-dependent diabetes mellitus (IDDM).
• Juvenile diabetes.
• Brittle diabetes.
• Sugar diabetes.

Type 1 diabetes accounts for between 5 out of 100 to 10 out of 100 diagnosed cases of diabetes in the U.S. Type 1 diabetes most often develops in children or young adults. But it can start at any age.

Experts don't know what causes type 1 diabetes. Genetic and environmental factors may play a role.

The body's immune system attacks and destroys the cells in the pancreas that make insulin. Insulin lets glucose enter the cells for energy. When glucose can't enter the cells, it builds up in the blood. Then the cells don't get enough nutrition. It also causes high blood sugar. People with type 1 diabetes must check their blood sugar levels regularly and take daily insulin shots or wear a pump that continually injects insulin.

In 2022, the FDA approved a medicine to help delay the onset of Stage 3 type 1 diabetes. This may be an option for people ages 8 and older who are at high risk or have early signs of type 1 diabetes.

Type 1 diabetes often appears suddenly. Symptoms may include:

• Abnormal thirst.
• Frequent and increased urination.
• Extreme hunger but loss of weight.
• Blurred vision.
• Nausea and vomiting.
• Extreme weakness and lack of energy (fatigue).
• Irritability and mood changes.
• Fungal (yeast) skin infections in the groin area.

In children, symptoms may seem like the flu. Bedwetting may be an important sign.

These symptoms may be caused by other conditions or health problems, including some medicines. Always see your doctor for a diagnosis.

There are several ways to diagnose diabetes. It's usually best for the tests to be repeated on a second day to make sure of the diagnosis.

• Fasting plasma glucose (FPG). This test checks your blood glucose levels after having no calorie intake for at least 8 hours. You may have water before this test is done, but nothing else. Diabetes is diagnosed at a fasting blood glucose level of 126 mg/dL or higher.
• Oral glucose tolerance test (OGTT). This is a 2-hour test that checks your blood glucose levels before and 2 hours after you drink a sugary drink. This test tells your doctor how your body processes glucose. Diabetes is diagnosed at a 2-hour blood glucose of 200 mg/dL or higher. If this test is used for screening, be sure you have at least 5.25 ounces (150 grams) of carbohydrates per day for 3 days before the test.
• A1C. The hemoglobin A1C test measures your average blood glucose for the past 2 to 3 months. Diabetes is diagnosed at an A1C of 6.5% or higher.
• Random glucose test. This blood test is done at any time of the day. Diabetes is diagnosed at blood glucose of 200 mg/dL or higher with the symptoms of hyperglycemia or hyperglycemic crisis.
• Insulin and c-peptide levels. Levels of these will be low or normal with type 1 diabetes but high with type 2 diabetes.
• Antibody levels. People with newly diagnosed type 1 diabetes will often have high levels of antibodies against certain proteins found in the pancreas.

Treatment will depend on your symptoms, age, and general health. It will also depend on how severe the condition is.

If you have type 1 diabetes, you will need daily shots of insulin to keep your blood sugar level in normal ranges. Other parts of treatment may include:

• Eating a diet to help manage blood sugar levels.
• Exercising to help the body use blood sugar efficiently.
• Monitoring blood sugar levels by fingerstick testing several times a day or by continuous monitoring, as directed by your doctor, and learning how to adjust your meals and insulin dose as needed.
• Having regular hemoglobin A1C testing. This is advised at least 2 times a year. You may need to do this more often if your blood sugar level stays too high.

Research is being done to find better ways to manage diabetes. This includes looking for other ways to take insulin such as through pens, inhalers, pills, or pumps. Researchers have also found some genetic markers for type 1 diabetes. Pancreas and islet cell transplants are considered experimental treatments.

Type 1 diabetes may cause:

• Hypoglycemia. This is low blood sugar, sometimes called an insulin reaction. It occurs when blood sugar drops below 70 mg/dL. This can happen if the last insulin dose was too high for the amount of food eaten.
• Hyperglycemia. This is high blood sugar that occurs when the body has too little insulin. It can be a sign that diabetes is not well controlled.
• Ketoacidosis. When your body doesn't have enough insulin to use glucose for energy, the liver creates ketones out of fat. These ketones are then sent out in the bloodstream to muscles and other tissues to be used for energy. This can be part of the normal body function. But with diabetes, ketones can build up to high levels and become a life-threatening condition, leading to coma or death.

Long-term complications of uncontrolled type 1 diabetes include:

• Heart disease.
• Kidney disease.
• Eye problems.
• Nerve problems.
• Foot problems.

• In type 1 diabetes, the body can't make insulin, or it makes very little insulin.
• It is an immune system disorder. The body's immune system destroys, or tries to destroy, the cells in the pancreas that make insulin.
• It most often develops in children or young adults. But it can start at any age.
• It often appears suddenly. Symptoms include abnormal thirst, frequent urination, blurred vision, nausea, and vomiting.
• For type 1 diabetes, you need daily insulin, either by injections or a pump that continuously delivers it under the skin. You also need to regularly check your blood sugar levels.

Tips to help you get the most from a visit to your doctor:

• Know the reason for your visit and what you want to happen.
• Before your visit, write down questions you want answered.
• Bring someone with you to help you ask questions and remember what your doctor tells you.
• At the visit, write down the name of a new diagnosis and any new medicines, treatments, or tests. Also write down any new instructions your doctor gives you.
• Know why a new medicine or treatment is prescribed and how it will help you. Also know what the side effects are and when they should be reported.
• Ask if your condition can be treated in other ways.
• Know why a test or procedure is recommended and what the results could mean.
• Know what to expect if you do not take the medicine or have the test or procedure.
• If you have a follow-up appointment, write down the date, time, and purpose for that visit.
• Know how you can contact your doctor if you have questions, especially after office hours and on weekends and holidays.