How do people get type 1 diabetes

Type 1 diabetes (Type 1 diabetes mellitus, Type 1 diabetes)

Type 1 diabetes is a metabolic disease that leads to increased blood sugar levels due to a mostly absolute lack of insulin. The development of type 1 diabetes is based on an autoimmune reaction in which the insulin-producing beta cells in the pancreas are destroyed by the body's own antibodies.

Short version:

  • About 40,000 people in Austria are affected by type 1 diabetes, including 3,500 children and adolescents.
  • Type 1 diabetes is often diagnosed in childhood and adolescence, as well as in young adults, but can also occur in older people (LADA diabetes)
  • In type 1 diabetes, the body's own antibodies destroy the insulin-producing beta cells in the pancreas and thus cause an insulin deficiency.
  • The exact causes of the development of the disease are not known to this day.
  • Typical symptoms are frequent urination, severe thirst, poor appetite and unwanted weight loss and physical exhaustion. However, type 1 diabetes can sometimes manifest itself slowly and with few symptoms.
  • The clinical diagnosis is made by a blood glucose determination and a urinalysis (evidence of glucose and ketone bodies). Severely decreased serum insulin and C-peptide as well as the detection of specific antibodies in the blood (attention: not always detectable) confirm the clinical diagnosis.
  • With good blood sugar control, the life expectancy of a person with type 1 diabetes is the same as that of a healthy person.
  • In cooperation with the Austrian Diabetes Society

What is Type 1 Diabetes?

Type 1 diabetes is a metabolic disorder that is too increased levels of sugar in the blood leads. The development of type 1 diabetes lies in the background Autoimmune reaction where the immune system turns against its own body. The insulin-producing beta cells of the pancreas are destroyed by the body's own antibodies (defense substances), which leads to an insulin deficiency. This usually happens in early childhood and adolescence, in rare cases not until later in adulthood.

Due to the absolute insulin deficiency, people with type 1 diabetes need insulin and have to supply this hormone artificially from the outside. A cure for this autoimmune disease is not yet possible. However, with the help of modern diabetes therapy, an almost unrestricted life can be led. This requires very good training and independence on the part of those affected.

+++ More on the topic: Autoimmune Disease +++

Who Does Type 1 Diabetes Affect?

Affects type 1 diabetes rather younger people (usually under 30), although elderly people can rarely get it. In contrast to type 2 diabetes, the patients are mostly normal or even slightly underweight. The reason for this is that due to the lack of insulin, the carbohydrates ingested through food get into the blood, but from there they cannot be absorbed into the cells without insulin.

In contrast to type 2 diabetes, there is one familial accumulation verifiable, but rather low. If both parents are people with type 1 diabetes, the risk of one child developing the same disease is around 20 percent. If only the father is affected, the risk is around five percent, in the case of the mother around 2.5 percent. Children of people with type 2 diabetes, on the other hand, develop 40 percent of type 2 diabetes, and 60 to 70 percent of both parents are affected.

+++ More on the topic: insulin and C-peptide +++

How does type 1 diabetes develop?

The hormone insulin is formed in the islets of Langerhans (island-like, embedded cell clusters of hormone-forming cells) of the pancreas. Most body cells need insulin in order to Absorb sugar from the bloodstream. In the cell, the sugar is burned into energy. If the sugar cannot be absorbed by the cells, the sugar concentration in the blood increases. If a certain concentration in the blood is exceeded, the sugar gets into the urine and is excreted through it.

In around 85 to 95 percent of all people with type 1 diabetes, antibodies that are responsible for destroying the body's own beta cells can be detected in the blood (the antibodies GAD, ICA, IA-2, IAA, zinc transporter 8). As a result, the pancreas cannot produce enough or no insulin. In addition, there is almost always a greatly reduced or negative C-peptide value (a value that reflects the insulin production of the pancreas). If the C-peptide is low, then insulin production is also low.

+++ More on the topic: Diabetes Type 2 +++

Causes of Type 1 Diabetes

The exact cause of this Malfunction of the immune system is still largely unknown today. It is believed that some Bacteria or viruses look so similar to the cells of the pancreas that the body not only renders these invading pathogens harmless, but also attacks its own cells.

Examples of viruses that are said to have a certain frequency in the development of type 1 diabetes are:

  • Coxsackie virus
  • Rubeola virus (rubella)
  • Echo viruses
  • Cytomegaly virus
  • Herpes virus
  • Representative of the enterovirus genus

To date, however, no clear evidence has been found.

There is also increasing evidence that vitamin D deficiency in infancy and early childhood is more likely to lead to type 1 diabetes.

+++ More on the topic: Vitamin D +++

What are the symptoms of type 1 diabetes?

The following symptoms can occur with high blood sugar:

  • frequent urination (polyuria)
  • severe thirst (polydipsia)
  • poor appetite
  • unwanted weight loss
  • Fatigue, tiredness and weakness
  • Dry mouth and night cramps in the calves
  • Visual disturbances
  • increased susceptibility to infection

These symptoms can be present in both type 1 and type 2 diabetes. Since the severe insulin deficiency in type 1 diabetes usually results in much higher blood sugar levels, the symptoms are correspondingly more pronounced and can develop within a few days to weeks.

+++ More on the topic: Diabetes in children +++

How is type 1 diabetes diagnosed?

The diagnosis of "type 1 diabetes" is based on a measurement of blood sugar and the HbA1c value ("long-term blood sugar"), as well as the detection of antibodies.

Blood glucose testing

In healthy people, the normal fasting blood sugar (before meals) is between 70 and 100 mg / dl in the blood. After eating, values ​​of 180-200 mg / dl can be measured even in healthy people. Strong evidence of overt (clinically recognizable) diabetes is Fasting blood sugar values ​​of over 126mg / dl and / or randomly measured blood sugar values ​​of over 200 mg / dl, whereby in the case of type 1 diabetes, significantly higher values ​​are often measured.

Hba1c value

This value indicates the average sugar concentration in the blood of the last (up to 12) weeks by showing how much blood sugar has permanently attached to the red blood pigment hemoglobin. HbA1c values ​​can also be measured in healthy people, which are below 5.7 percent. HbA1c values ​​between 6.0 and 6.5% correspond to a "prediabetic" metabolic situation in one HbA1c over 6.5% is called manifest diabetes. When diagnosed for the first time, the HbA1c value is well above this limit value in the majority of cases. The HbA1c is also suitable for monitoring therapy. This value is used to determine the mean blood sugar level for the last three to four months.

Oral glucose tolerance test (oGTT)

In this test, a sugary solution with a total of 75 grams of sugar is drunk and the blood sugar is then determined several times. Manifest diabetes is present if the measured Value after two hours still higher than 200mg / dl prediabetes is at a 2-hour value above 140 mg / dl.

+++ More on the topic: Diabetes and Pregnancy +++

Treatment of type 1 diabetes

Type 1 diabetes is caused by a lack of insulin. This deficiency is treated by giving this hormone. Insulin is injected under the skin (subcutaneously) every day; the exact amount depends on the carbohydrate content of the food (bolus requirement) and the basic requirement (basal requirement) and varies from person to person. In addition, the patient's blood sugar is measured about five times a day and used as a starting value for the blood sugar corrections. A newer way of measuring blood sugar is continuous glucose measurement (CGM), in which a tiny sensor is placed under the skin and measures the sugar concentration there every few minutes.

+++ More on the topic: Treatment of type 1 diabetes +++

Medical check-ups for type 1 diabetes

The recommended medical check-ups will help control blood sugar levels. They give the patient and the doctor feedback on how well the diabetes is controlled and help to avoid secondary and concomitant diseases. The medical checks include:

  • body weight
  • Blood pressure
  • Lipid status (blood lipids)
  • History of hypoglycaemia (low blood sugar)
  • HbA1c value
  • Sensitivity and blood circulation in the feet (foot inspection)
  • Kidney function
  • Electrocardiogram (EKG)
  • Eye examination (at the ophthalmologist)
  • Nerve examination (at the neurologist)

+++ More on the topic: What is the difference between type 1 and type 2 diabetes? +++


The high blood sugar content in the vessels in type 1 diabetes is unfavorable in the long term. The sugar molecules are deposited on all kinds of proteins in the blood and on the vessel walls and interfere with their function. In the long term, this can lead to the so-called late diabetic complications in the large and small vessels, as well as late damage to the eyes, kidneys and nerves. These only develop over time and can be held back with good blood sugar control.

The most important part of a treatment is one good sugar adjustment and control. Blood sugar should be as "close to normal" as possible, but values ​​that are too low should also be avoided. Treatment of possible concomitant diseases and good blood pressure and blood lipid settings are also essential.

Extensive studies have shown that good control of diabetes and accompanying diseases can reduce or even prevent the risk of late-stage diabetic damage and enable normal life expectancy.

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Univ. Prof. Dr. Martin Clodi (2015), Christopher Waxenegger (2021)
Medical review:
Prim. Univ.-Prof. Dr. Peter Fasching
Editorial editing:
Helga Quirgst, MSc (2015), Astrid Leitner (2021)

Status of medical information:

Austrian Diabetes Society (ÖDG): Diabetes mellitus - guidelines for practice, 2019

German Diabetes Society (DDG) S3 guideline: Therapy of type 1 diabetes, 2nd edition, 2018

Geisslinger G, Menzel S, Gudermann T, Hinz B and Ruth P. Mutschler Drug effects: pharmacology, clinical pharmacology, toxicology. Wissenschaftliche Verlagsgesellschaft Stuttgart, 11th edition, 2020

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ICD-10: E10