Type 1 diabetes is a lifelong autoimmune condition in which the immune system destroys the cells in the pancreas that make insulin, so the body can no longer move sugar out of the blood and into cells, and insulin has to be replaced every day [1,3,4].
This page provides general information. It does not replace advice from a doctor or another qualified healthcare professional.
Food is broken down into a sugar called glucose, which travels in the blood. Insulin, a hormone made by the pancreas, lets glucose move from the blood into cells for energy [3].
In type 1 diabetes the immune system, which normally fights infections, destroys the cells in the pancreas that make insulin, called beta cells. The body then makes little or no insulin, and glucose builds up in the blood. A condition in which the immune system attacks the body’s own cells is autoimmune [1,3,4].
Type 1 diabetes is not caused by diet or lifestyle. The belief that it is causes real hurt. Eating sugar does not cause it, and nothing a person ate or avoided would have prevented it [4,9].
It is a different condition from type 2 diabetes, and confusing the two is common. In type 2 diabetes the body makes insulin but responds poorly, and treatment usually starts with other medicines. In type 1 the insulin-making cells are gone, so insulin is needed from diagnosis and for life [3,4,19]. Type 2 diabetes has its own guide.
Type 1 diabetes has stages, and the first two have no symptoms. The immune attack begins months or years before anyone feels unwell, and shows in a blood test as markers called islet autoantibodies. Stage 1 means two or more markers with normal glucose, stage 2 means glucose has begun to rise but not enough to diagnose, and stage 3 is when it is high enough. Someone at stage 1 or 2 already has the condition, not a risk of it [1,8].
An estimated 9.5 million people of all ages were living with type 1 diabetes worldwide in 2025, and around 513,000 were newly diagnosed that year. These are modeled estimates of diagnosed cases, and 119 of the 202 countries covered had no local data at all [2].
The age pattern surprises people. Of the 9.15 million estimated for 2024, only about 19.8% were under 20, while 68.6% were aged 20 to 59. Type 2 diabetes is over 90% of all diabetes worldwide, which is one reason type 1 gets mistaken for it [1].
Nobody knows why the immune system turns on the beta cells. Current understanding is that it takes inherited factors plus something in the environment, possibly a common virus [1,4,9].
Genes raise the chances, and most people affected have no family history. A gene is a set of instructions passed from parent to child. Many gene variants have been linked to type 1 diabetes, most involved in the immune system. Having a parent, brother or sister with it raises the chances to about 5% by age 20, against about 0.3% in the general population. Even so, more than 90% of children diagnosed have no family history [8,10].
Once two or more markers are confirmed, needing insulin eventually is close to certain [8].
Symptoms appear over days or weeks and can be severe. The main ones are urinating more than usual, especially at night, being very thirsty, feeling very tired and losing weight without trying, taught in the United Kingdom as the 4 Ts: toilet, thirsty, tired, thinner [5].
Other signs include blurred vision, increased hunger and repeated infections. In young children a return to bed-wetting can be the first sign [3,5].
When to seek urgent help. Anyone with these symptoms should be seen the same day where possible, which in the United Kingdom means an urgent appointment or NHS 111 [5].
Call emergency services, 999 in the United Kingdom or 911 in the United States, if someone with those symptoms also has any of the following [5]:
These can be signs of diabetic ketoacidosis, often shortened to DKA. Without insulin the body burns fat instead, producing acids called ketones that make the blood dangerously acidic. DKA is life-threatening and needs hospital treatment straight away [1,3,5]. It is common at diagnosis: across 13 high-income countries the pooled rate in children was 29.9%, and in the United Kingdom more than a quarter of children are already in DKA when diagnosed [1,11]. Do not drive there yourself. Ask someone else to drive, or call an ambulance [5].
A family doctor usually starts with a finger-prick test for blood glucose, and may test urine. If the result suggests type 1 diabetes, the person sees a hospital specialist that day to start treatment [5].
Diagnosis rests on blood glucose measurements, taken at random, after fasting, or as an HbA1c test showing average glucose over two to three months. These show diabetes, not the type [3].
Telling type 1 from type 2 takes extra tests. An autoantibody test looks for the immune markers, and a C-peptide test shows how much insulin the pancreas is still making [3,4].
Adults are frequently misdiagnosed as having type 2 diabetes. Up to 40% of adults over 30 living with type 1 diabetes may have been told at first that they had type 2, driven by an assumption that an adult with diabetes has type 2 by default, and by poor access to the tests that would settle it [3,13]. Anyone not improving on tablets can ask for them.
There is no cure. Insulin replaces what the body can no longer make and is needed every day for life. It cannot be a tablet, since stomach acid destroys it [4].
Insulin. Most people use more than one type, by injection with a pen several times a day or through a pump worn against the skin. Doses are matched to activity and to the carbohydrate in food, a skill taught on structured courses everyone should be offered [3,6,16].
Monitoring and automated insulin delivery. A continuous glucose monitor, or CGM, is a sensor worn under the skin that tracks glucose day and night and alarms when levels go too high or low [3,7]. Linking a CGM to a pump, with software deciding the doses, creates a hybrid closed loop system, or artificial pancreas. These have changed daily life substantially, reducing low glucose episodes and easing the workload of constant decisions [6,13]. Guidance in England recommends them for children, in pregnancy, and for adults whose glucose stays high despite other treatment [17]. This is optimal care, and it is expensive and only widely available in some high-income countries [1].
Low blood glucose. Too much insulin relative to food or activity causes hypoglycemia, or a hypo. Signs include hunger, shaking, sweating and dizziness, treated quickly with a sugary drink or glucose tablets. Some people stop noticing the warning signs, which needs specialist help [3,7].
Access is deeply unequal. In many countries, especially in poorer families, access to insulin, monitoring equipment and education is limited, which leads to avoidable emergencies and early death. The remaining life expectancy of a 10-year-old diagnosed in 2024 ranged from an estimated 6 years in one sub-Saharan African country to over 66 years in some high-income ones [1].
Care is shared between a specialist team and the person, with a yearly review, HbA1c checks every three to six months, and regular eye and foot checks [6]. Practical things help: carrying something sugary, carrying medical identification, making sure family, school or colleagues know how to recognize a hypo, and agreeing a plan for illness. Drivers who use insulin must tell the licensing authority, and pregnancy is planned with the team [7].
The mental load is real, and it is not a discipline problem. Type 1 diabetes asks for decisions all day, every day, and that is wearing. Diabetes distress is the name for feeling overwhelmed by the relentlessness of it, and around one in four people with type 1 diabetes have high levels of it. Readings are numbers, not a verdict on effort, which is why specialists avoid calling them good or bad. Anyone struggling is better off saying so than managing alone [12].
Clinical trials test whether a treatment works and is safe. Type 1 diabetes research is active across immune treatments, cell therapies and technology. Deciding whether to look into a study is personal, and it helps to take it in steps.
Worth being clear on what a study involves:
Every trial has rules about who can take part, called eligibility criteria. For a type 1 diabetes study they might include a confirmed diagnosis with specified autoantibodies present, a set age range, a set time since diagnosis, a C-peptide level inside set limits showing how much insulin the body still makes, an HbA1c inside a set range, and no other medicine or condition making the treatment unsafe.
trialport’s medifit helps people consider information related to possible medical suitability. It does not diagnose a condition, confirm eligibility or replace formal screening by the study team.
Explore type 1 diabetes clinical trials through trialport
A study can look right on paper and still be hard in practice:
trialport’s readifit helps people reflect on their understanding, motivation, time, routines, support, emotions and practical arrangements.
Useful questions to put to a research team:
Taking part is voluntary. A person can ask questions, speak with people they trust and choose not to participate.
Search for clinical trials at app.trialport.com.
Study status checked: 3 August 2026. Research moves quickly, so this list will date. For current information, search app.trialport.com.
Many countries have a general diabetes organization rather than one specific to type 1, and the treating clinic is then the best route.
Theresa May, later Prime Minister of the United Kingdom, was diagnosed with type 1 diabetes in 2013 while Home Secretary, in her fifties. Doctors first thought she had type 2, and it was two months before that was corrected. She described how hard the symptoms were to read: “The symptoms are tiredness, drinking a lot of water, losing weight, but it’s difficult to isolate things.” She called it “a real shock” [21,22].
Sonia Sotomayor, a justice of the United States Supreme Court, was diagnosed at seven after fainting in church, being constantly thirsty and wetting the bed. In 2011 she told a gathering of children with type 1 diabetes, of those early symptoms, “I was ashamed,” and described the first time she saw her mother cry. When the doctor said diabetes was not so bad, she thought, “If it isn’t so bad, why is my mommy crying?” [23]
Did eating too much sugar cause type 1 diabetes?
No. It is autoimmune, and diet and lifestyle habits do not cause it. Nothing a person or parent did brought it on [4,9].
What is the difference between type 1 and type 2 diabetes?
In type 1 diabetes the immune system destroys the insulin-making cells, so insulin is needed for life. In type 2 the body makes insulin but responds to it poorly. See our type 2 diabetes guide [3,4].
Can adults get type 1 diabetes?
Yes, commonly. In 2024 an estimated 56.5% of new diagnoses were in people aged 20 or older [1], and up to 40% of adults over 30 with type 1 are first told they have type 2 [13].
Is there a cure, and can it be prevented?
Neither, at present, though treatment has improved a great deal and research is active [18,20]. Teplizumab can delay the point at which insulin is needed at stage 2, which is not prevention [8].
What are the warning signs of DKA?
Symptoms worsening quickly, stomach pain, being sick, sleepiness or confusion, fast deep breathing, sweet or fruity-smelling breath. Call emergency services [5].
Will type 1 diabetes shorten my life?
Life expectancy is still reduced, by up to about 8 years, and that gap reflects access to care as much as anything else [7,13].
Written by: trialport editorial team
Reviewed by: Keith Berelowitz, Founder and CEO, trialport
Reviewed on: 3 August 2026
Next review due: 3 August 2027
References last checked: 3 August 2026