Condition5 min read
Type 1 diabetes
T1DT1DM
An autoimmune condition in which the immune system destroys the insulin-making cells of the pancreas, so the body makes little or no insulin. People need insulin and regular glucose monitoring, and must know the warning signs of ketoacidosis.
It is an autoimmune disease. Its symptoms appear quickly: frequent urination and thirst, hunger despite eating, tiredness and blurred vision, unexplained weight loss. The most serious associated condition is diabetic ketoacidosis, which is an emergency.
It is diagnosed by glucose and A1C tests and confirmed by autoantibodies and a C-peptide test. Treatment includes insulin therapy (injections, pen or pump), glucose monitoring with meters or continuous glucose monitoring (CGM) and artificial pancreas systems, and islet or pancreas transplant in selected cases.
In one minute12
- What is it?
- An autoimmune disease in which the immune system destroys the insulin-producing cells of the pancreas.
- Who is usually affected?
- The NIDDK estimates that about 1.7 million adults and 304,000 children and adolescents were affected in the United States in 2021.
- Acute or chronic?
- Chronic, requiring lifelong insulin and glucose monitoring.
- Main symptoms
- Thirst, frequent urination, hunger, tiredness and weight loss.
- Red flags?
- Yes: signs of ketoacidosis and severe hypoglycaemia.
- Preventable?
- This page's sources do not cover preventing the disease itself; its acute complications are avoided with follow-up, ketone testing and not stopping insulin.
What is it?
In type 1 diabetes the body produces little or no insulin; it is an autoimmune disease in which the immune system destroys the insulin-producing cells of the pancreas.
According to the NIDDK in 2021: about 1.7 million American adults and 304,000 children and adolescents have type 1.
Symptoms
Frequent urination and intense thirst, hunger despite eating, blurred vision, tiredness, slow-healing wounds, recurrent infections, and unexplained weight loss.
Symptoms appear in children over a short period, and may develop more gradually in some adults.
When do symptoms appear?
The disease may first appear as ketoacidosis, especially in children who have not been diagnosed.
How is it diagnosed?
Random or fasting plasma glucose, the A1C test (a three-month average), autoantibodies to confirm type 1, and the C-peptide test to measure the pancreas's insulin production.
Treatment
The treatment categories usually used are listed here; this is not a prescription. The doctor chooses the plan according to each person's condition; do not change any medicine or dose without a specialist.
Insulin therapy with different types given by injection, pen or pump, glucose monitoring with devices or continuous sensing, artificial pancreas systems, and islet or pancreas transplant in selected cases. Doses are determined by the treating team.
Complications
Chronic high glucose harms the heart, kidneys, nerves, eyes, feet and teeth. Other complications include ketoacidosis, hypoglycaemia unawareness, psychological difficulties, eating disorders and osteoporosis.
Ketoacidosis: ketones build up in the blood because of a lack of insulin. Its symptoms are thirst, frequent urination, abdominal pain, nausea, deep breathing, a fruity smell on the breath, tiredness, confusion and blurred vision, and it usually develops within 24 hours.
Prevention
Follow the treating team's plan, measure glucose regularly, test ketones when glucose is high or when ill, and do not stop insulin even when not eating (according to the NHS). (Prevention of acute complications, not of the disease itself.)
When do you need urgent help?
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See your doctor within days
- Repeated high or unstable glucose readings need the plan adjusted with the treating team.1
Educational content only — no diagnosis, and no substitute for a clinician.
Common questions
Does someone with type 1 need insulin?
Yes; because the body produces little or no insulin, and insulin therapy is the basis of treatment according to the NIDDK.1
Questions for your doctor
- What are my HbA1c and glucose targets?
- When do I test ketones and what do I do when they are high?
- Would I benefit from a continuous sensor or a pump?
- How do I handle exercise, illness and fasting?
- What is the annual testing schedule (eye, kidney, foot)?
References
- 1NIDDK / NIH. What is type 1 diabetes?. www.niddk.nih.gov/health-information/diabetes/overview/what-is-diabetes/type-1-diabetesHealth agencies & guidelines · Accessed 2026-10-05
- 2NHS. Diabetic ketoacidosis. www.nhs.uk/conditions/diabetic-ketoacidosis/Health agencies & guidelines · Accessed 2026-10-03
Review status: Edited content · Last updated:
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Educational content only — no diagnosis, and no substitute for a clinician.