How does Type 1 diabetes work?
Type 1 diabetes is a lifelong condition that causes a person’s blood sugar (glucose) level to become too high. But type 1 diabetes doesn’t begin all at once. It develops gradually in stages, often before any symptoms appear.1 This means doctors can screen for early signs of the condition, helping to reduce the chance of starting the journey with a medical emergency.2
Understanding autoimmune type 1 diabetes
Autoimmune type 1 diabetes is a condition where the immune system mistakenly attacks insulin-producing beta cells in the pancreas.3 It isn’t caused by eating too much sugar or having an unhealthy lifestyle.4 While certain factors like genetics or the environment may play a role, it can affect people of any age, including children, teens, and adults.3
What is autoimmunity?
Autoimmunity happens when the immune system mistakenly attacks the body’s own healthy cells. Instead of responding to viruses or bacteria, the immune system produces autoantibodies that target parts of the body, such as the insulin-producing beta cells in the pancreas.5
These beta cells aren’t harmful, but the immune system mistakenly sees them as threats and tries to destroy them.3
In autoimmune type 1 diabetes, the body makes certain proteins called autoantibodies that target the beta cells and mark them for destruction. These include:
- GAD653
- IA-23
- ZnT83
- IAA (insulin autoantibodies)3
- ICA (islet cell antibodies)3
While these autoantibodies aren’t what destroy the beta cells, their presence is a sign of the autoimmune attack. Testing for these autoantibodies through screening is therefore valuable to identify people with an increased chance of developing autoimmune type 1 diabetes, even before symptoms appear.3
How does the immune system attack the pancreas?
In autoimmune type 1 diabetes, the body’s immune system mistakenly attacks the pancreas, specifically targeting the insulin-producing beta cells. Immune cells mistakenly see proteins on the beta cells as harmful, which leads to T cells (the immune system's main protectors) attacking the beta cells.1 Other immune cells also contribute to this response, and can be found in people with autoimmune type 1 diabetes.6
Over time, this autoimmune response leads to the gradual decline of insulin-producing beta cells in the pancreas. As these cells are lost, the body becomes less able to produce insulin naturally.6
What happens when the body can’t produce enough insulin?
Insulin is a hormone made by the pancreas. It helps move glucose from the food we eat into the body’s cells, where it is used for energy. When the pancreas is working properly, insulin helps keep glucose levels balanced throughout the day.7
Without enough insulin, glucose can’t enter the cells as it should. Instead, it starts to build up in the bloodstream, which leads to irregularly high glucose levels.7 This buildup means that, even though there’s glucose in the blood, the cells can’t use it effectively for energy.7 Learn more about the causes and risk factors of autoimmune type 1 diabetes.
How does the body manage without insulin?
When the body doesn’t have enough insulin, it can’t move glucose from the blood into the cells where it’s needed for energy. To make up for this, the body starts breaking down fat stores for fuel instead. This process releases substances called ketones.8
But in people with autoimmune type 1 diabetes, this shift can quickly become harmful. Without insulin to keep things in balance, fat breakdown speeds up, and ketones begin to build up in the blood. At the same time, the body’s ability to clear ketones is reduced.8
If ketone levels become too high, it can lead to diabetic ketoacidosis (DKA), which is a medical emergency. However, early detection through screening can help track the progression of autoimmune type 1 diabetes and reduce the likelihood of starting the journey with a medical emergency.8
Why can’t the body repair itself in autoimmune type 1 diabetes?
Unlike some other cells in the body, insulin-producing beta cells don’t regenerate once they’ve been destroyed.9
Adding to this challenge, the immune system doesn’t stop attacking beta cells after the disease starts. This ongoing immune activity makes it impossible for the pancreas to recover or repair itself.9
As such, unlike type 2 diabetes or prediabetes, autoimmune type 1 diabetes is considered irreversible and can’t be reversed through diet, exercise, or other lifestyle changes.4 As a result, people with autoimmune type 1 diabetes need to replace the missing insulin every day, either through injections or an insulin pump, to keep their glucose levels in a safe range.1 Uncover other common myths around autoimmune type 1 diabetes.
How does autoimmune type 1 diabetes develop?
Autoimmune type 1 diabetes develops over time. It starts with presymptomatic stages (Stage 1 or 2) when the immune system mistakenly starts attacking the insulin-producing beta cells in the pancreas. In Stage 2, the immune attack continues, and glucose levels begin to change. In Stage 3, known as symptomatic autoimmune type 1 diabetes, symptoms appear, and insulin production is significantly affected.1
While symptoms don’t emerge until later, one of the biggest breakthroughs in recent years is that we can now detect autoimmune type 1 diabetes early through screening, before symptoms show. This is done through a simple blood test that looks for autoantibodies. 1,3
Understanding that autoimmune type 1 diabetes develops in stages allows for better planning. By tracking how glucose levels and insulin production change over time, healthcare professionals can decide when insulin therapy might be needed. 1
If autoimmune type 1 diabetes runs in your family, or if someone has another autoimmune condition like celiac disease or thyroid disease, it’s a good idea to talk to your doctor about screening.10 Detecting the condition early can reduce the chance of a medical emergency.1
References
- Insel RA, Dunne JL, Atkinson MA, et al. Staging Presymptomatic Type 1 Diabetes: A Scientific Statement of JDRF, the Endocrine Society, and the American Diabetes Association. Diabetes Care. 2015;38(10):1964-1974. doi:https://doi.org/10.2337/dc15-1419
- Cherubini V, Grimsmann JM, Åkesson K, et al. Temporal trends in diabetic ketoacidosis at diagnosis of paediatric type 1 diabetes between 2006 and 2016: results from 13 countries in three continents. Diabetologia. 2020;63(8):1530-1541. doi:https://doi.org/10.1007/s00125-020-05152-1
- Lucier J, Mathias PM. Type 1 Diabetes. Nih.gov. Published October 5, 2024. Accessed May 9, 2025. https://www.ncbi.nlm.nih.gov/books/NBK507713/
- Singh M. Myths about Diabetes among Adolescents and Their Parents. Journal of Child and Adolescent Behaviour. 2014;02(04). doi:https://doi.org/10.4172/2375-4494.1000164
- Farzana Yasmeen, Pirzada RH, Ahmad B, Choi B, Choi S. Understanding Autoimmunity: Mechanisms, Predisposing Factors, and Cytokine Therapies. International Journal of Molecular Sciences. 2024;25(14):7666-7666. doi:https://doi.org/10.3390/ijms25147666
- Campbell-Thompson M, Rodriguez-Calvo T, Battaglia M. Abnormalities of the Exocrine Pancreas in Type 1 Diabetes. Current Diabetes Reports. 2015;15(10). doi:https://doi.org/10.1007/s11892-015-0653-y
- Rahman S. Role of Insulin in Health and Disease: an Update. International Journal of Molecular Sciences. 2021;22(12):6403. doi:https://doi.org/10.3390/ijms22126403
- Preeti Kanikarla-Marie, Jain SK. Hyperketonemia and ketosis increase the risk of complications in type 1 diabetes. Free Radical Biology and Medicine. 2016;95:268-277. doi:https://doi.org/10.1016/j.freeradbiomed.2016.03.020
- Oram RA, Sims EK, Evans-Molina C. Beta cells in type 1 diabetes: mass and function; sleeping or dead? Diabetologia. 2019;62(4):567-577. doi:https://doi.org/10.1007/s00125-019-4822-4
- Barker JM. Type 1 Diabetes-Associated Autoimmunity: Natural History, Genetic Associations, and Screening.The Journal of Clinical Endocrinology & Metabolism. 2006;91(4):1210-1217. doi:https://doi.org/10.1210/jc.2005-1679
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