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Type 1 diabetes
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Condition

Type 1 diabetes

Type 1 diabetes is an autoimmune disorder where the pancreas stops producing insulin, leading to high blood glucose levels.

Description

Type 1 diabetes is a disorder characterized by abnormally high levels of blood glucose. In this form of diabetes, specialized cells in the pancreas called beta cells stop producing insulin. Insulin controls how much glucose is passed from the blood into cells for energy. A lack of insulin results in the inability to use glucose for energy or to control the amount of glucose in the blood.

Uncontrolled type 1 diabetes can lead to a life-threatening complication called diabetic ketoacidosis. Because cells cannot take in glucose, the body breaks down fats for energy, producing waste products called ketones. These can build up to toxic levels, causing symptoms such as rapid breathing, a fruity odor on the breath, nausea, vomiting, and stomach pain.

Over many years, chronic high blood glucose can cause damage to blood vessels and nerves, leading to:

  • Diabetic retinopathy (vision loss or blindness)
  • Diabetic nephropathy (kidney damage or failure)
  • Diabetic neuropathy (pain, tingling, or loss of sensation, especially in the feet)
  • Increased risk of heart attacks and strokes

Frequency

Type 1 diabetes occurs in 10 to 20 per 100,000 people per year in the United States. By age 18, approximately 1 in 300 people in the United States develop the condition. It accounts for 5 to 10 percent of diabetes cases worldwide, and its incidence has been increasing by 2 to 5 percent each year for the past 20 years.

Causes

Type 1 diabetes is generally considered an autoimmune disorder, where the immune system attacks the body's own tissues—specifically the insulin-producing beta cells in the pancreas. The risk is increased by certain variants of the HLA-DQA1, HLA-DQB1, and HLA-DRB1 genes, which belong to a family of genes called the HLA complex. These genes help the immune system distinguish the body's own proteins from foreign invaders. Certain combinations of these variations, called a haplotype, are associated with a higher risk of an inappropriate immune response to beta cells.

Inheritance

A predisposition to develop type 1 diabetes is passed through generations in families, but the inheritance pattern is unknown.

Other Names for This Condition

  • Autoimmune diabetes
  • Diabetes mellitus type 1
  • Diabetes mellitus, insulin-dependent
  • Diabetes mellitus, type 1
  • IDDM
  • Insulin-dependent diabetes mellitus
  • JOD
  • Juvenile diabetes
  • Juvenile-onset diabetes
  • Juvenile-onset diabetes mellitus
  • T1D
  • Type 1 diabetes mellitus

Frequently Asked Questions

The honeymoon phase is a temporary period occurring shortly after diagnosis where remaining pancreatic beta cells briefly recover and produce small amounts of insulin. During this time, blood glucose levels may normalize more easily, and daily external insulin requirements often drop dramatically. However, this phase typically lasts from a few months to over a year before ending as autoimmune destruction completes. Insulin therapy must never be stopped entirely during this phase to avoid sudden diabetic ketoacidosis.
The 15-15 rule is a standard rescue protocol for blood glucose readings below 70 mg/dL without loss of consciousness. Consume 15 grams of fast-acting simple carbohydrates—such as 4 ounces of fruit juice, half a can of regular soda, or 3 to 4 glucose tablets. Wait 15 minutes and recheck blood glucose. If levels remain under 70 mg/dL, repeat with another 15 grams of fast-acting carbohydrate until levels stabilize, then eat a meal or complex carbohydrate snack with protein to prevent another drop.
Yes. First-degree relatives of individuals with type 1 diabetes can undergo blood screening for islet autoantibodies, such as GAD65, IA-2, and ZnT8. The detection of two or more autoantibodies indicates early-stage, presymptomatic autoimmune activity against beta cells. Early identification allows close metabolic surveillance, drastically lowers the risk of severe diabetic ketoacidosis at diagnosis, and may qualify individuals for preventative immunotherapies designed to delay clinical onset.
During acute illnesses like viral infections, stress hormones cause blood glucose and ketone production to surge even if food intake decreases. Patients should check blood sugar and ketone levels every 2 to 4 hours, continue basal insulin without interruption, drink plenty of carbohydrate-free hydrating fluids with electrolytes, and take supplemental fast-acting insulin corrections as prescribed. Urgent medical evaluation is necessary if ketones remain moderate-to-high, fever is persistent, or intractable vomiting prevents fluid retention.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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