Mayo Clinic

Overview

Type 1 diabetes, once known as juvenile diabetes or insulin-dependent diabetes, is a chronic condition in which the pancreas produces little or no insulin. Insulin is a hormone needed to allow sugar (glucose) to enter cells to produce energy.

Different factors, including genetics and some viruses, may contribute to type 1 diabetes. Although type 1 diabetes usually appears during childhood or adolescence, it can develop in adults.

Despite active research, type 1 diabetes has no cure. Treatment focuses on managing blood sugar levels with insulin, diet and lifestyle to prevent complications.

Symptoms

Type 1 diabetes signs and symptoms can appear relatively suddenly and may include:

  • Increased thirst
  • Frequent urination
  • Bed-wetting in children who previously didn't wet the bed during the night
  • Extreme hunger
  • Unintended weight loss
  • Irritability and other mood changes
  • Fatigue and weakness
  • Blurred vision

When to see a doctor Consult your doctor if you notice any of the above signs and symptoms in you or your child.

Causes

The exact cause of type 1 diabetes is unknown. Usually, the body's own immune system — which normally fights harmful bacteria and viruses — mistakenly destroys the insulin-producing (islet, or islets of Langerhans) cells in the pancreas. Other possible causes include:

  • Genetics
  • Exposure to viruses and other environmental factors

The role of insulin

Once a significant number of islet cells are destroyed, you'll produce little or no insulin. Insulin is a hormone that comes from a gland situated behind and below the stomach (pancreas).

  • The pancreas secretes insulin into the bloodstream.
  • Insulin circulates, allowing sugar to enter your cells.
  • Insulin lowers the amount of sugar in your bloodstream.
  • As your blood sugar level drops, so does the secretion of insulin from your pancreas.

The role of glucose

  • Glucose — a sugar — is a main source of energy for the cells that make up muscles and other tissues.
  • Glucose comes from two major sources: food and your liver.
  • Sugar is absorbed into the bloodstream, where it enters cells with the help of insulin.
  • Your liver stores glucose as glycogen.
  • When your glucose levels are low, such as when you haven't eaten in a while, the liver breaks down the stored glycogen into glucose to keep your glucose levels within a normal range.

In type 1 diabetes, there's no insulin to let glucose into the cells, so sugar builds up in your bloodstream. This can cause life-threatening complications.