Diabetes I / II

What is type 1 diabetes?

In type 1 diabetes, the body can’t make insulin. Insulin is needed to help glucose enter cells for energy. Without insulin, glucose builds up in the blood. This causes high blood glucose or high blood sugar. Type 1 diabetes may also be known as:

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

Type 1 diabetes accounts for 5% to 10% of all diagnosed cases of diabetes in the U.S. Type 1 diabetes most often develops in children or young adults, but can start at any age.

What causes type 1 diabetes?

The cause of type 1 diabetes is unknown. It’s thought that genetic and environmental factors be involved.

The body's immune system attacks and destroys the cells in the pancreas that make insulin. Insulin lets glucose to enter the cells for energy. When glucose can’t enter the cells, it builds up in the blood. This deprives the cells of nutrition. It also results in high blood sugar. People with type 1 diabetes must take daily insulin shots and regularly check their blood sugar levels.

What are the symptoms of type 1 diabetes?

Type 1 diabetes often appears suddenly. Symptoms may include:

  • Unusual thirst
  • Frequent passing urine
  • Extreme hunger but loss of weight
  • Blurred vision
  • Nausea and vomiting
  • Extreme weakness and fatigue
  • Irritability and mood changes

In children, symptoms may be similar to those of having the flu.

The symptoms of type 1 diabetes may look like other conditions or health problems. Always consult your doctor for a diagnosis.

How is type 1 diabetes diagnosed?

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

  • A1C.  The hemoglobin A1C test measures your average blood glucose for the past 2 to 3 months. Diabetes is diagnosed at an A1C of greater than or equal to 6.5%.
  • Fasting plasma glucose (FPG). This test checks your blood glucose levels after fasting overnight. You may have water before this test is done, but nothing else. Diabetes is diagnosed at a fasting blood glucose of greater than or equal to 126 mg/dl.
  • 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 greater than or equal to 200 mg/dl.
  • Random glucose test. This blood test is done at any time of the day. Diabetes is diagnosed at blood glucose of greater than or equal to 200 mg/dl with the symptoms hyperglycemia or hyperglycemic crisis.


Your health care provider will figure out the best treatment based on:

  • How old you are
  • Your overall health and medical history
  • How sick you are
  • How well you can handle specific medications, procedures, or therapies
  • How long the condition is expected to last
  • Your opinion or preference

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 several times a day, as directed by your doctor
  • Having regular hemoglobin A1c testing. This is recommended at least twice a year or more often if your blood sugar level stays too high.

Research is underway to find better ways to manage diabetes. This includes looking for other way to take insulin such as through inhalers, pills, or pumps. They have also identified some genetic markers for type 1 diabetes. Pancreas and islet cell transplants are considered experimental treatment.

What are the complications of type 1 diabetes?

Type 1 diabetes may cause the following:

  • Hypoglycemia. This is low blood sugar, sometimes called an insulin reaction. It occurs when blood sugar drops below 70 mg/dl.
  • Hyperglycemia. This is high blood sugar, occurs when blood sugar is too high. It can be a sign that diabetes is not well controlled.
  • Ketoacidosis. This is a form of severe dehydration due to untreated or poorly treated diabetes. It can result in loss of consciousness or brain damage.

Long-term complications of uncontrolled type 1 diabetes include:

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

Key points

  • Type 1 diabetes is an immune system disorder in which the body's immune system destroys, or tries to destroy, the cells in the pancreas that make insulin.
  • When glucose can’t enter the cells, it builds up in the blood. This deprives the cells of nutrition.
  • For type 1 diabetes, you need daily insulin injections. You also need to regularly check your blood sugar levels.

Next steps

Tips to help you get the most from a visit to your health care provider:

  • Before your visit, write down questions you want answered.
  • Bring someone with you to help you ask questions and remember what your provider tells you.
  • At the visit, write down the names of new medicines, treatments, or tests, and any new instructions your provider gives you.
  • If you have a follow-up appointment, write down the date, time, and purpose for that visit.
  • Know how you can contact your provider if you have questions.
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