Diabetes mellitus refers to various forms of diabetes. What all these forms have in common at their onset is high blood sugar levels, also known as hyperglycemia

Type 2 Diabetes

Type 2 diabetes is the most common form. Together with a hereditary disposition for type 2 diabetes, overweight and a lack of physical activity are the causes of the disease.
Type 2 diabetes: an overview (diabinfo.de)

Prediabetes—The Precursor to Type 2 Diabetes

It is therefore important to already recognize prediabetes, the precursor to type 2 diabetes. Blood sugar levels are already elevated, though not yet high enough to be classified as type 2 diabetes. It is a metabolic disorder that often develops over years without accompanying symptoms. Specific lifestyle measures can lower blood sugar values at an early stage and thus reduce the risk of developing type 2 diabetes.
What is prediabetes? (diabinfo.de)

Type 1 Diabetes

Type 1 diabetes usually occurs during childhood and adolescence, but can also appear in adulthood. It is caused by an autoimmune process that completely destroys the insulin-producing beta cells in the islets of Langerhans in the pancreas.
Type 1 diabetes: an overview (diabinfo.de)

Other Forms

In addition to type 1 and type 2 diabetes, gestational diabetes is also widespread.
Gestational diabetes: an overview (diabinfo.de)

There are also other rarer forms of diabetes, such as MODY diabetes.

Research news: Diabetes Subtypes

It has been shown that diabetes is more diverse than the long-established classification into type 1 and type 2 diabetes would suggest.

Subtypes of Prediabetes

In the DZD Prediabetes Lifestyle Intervention Study (PLIS), six subtypes were already identified in the preliminary stages of diabetes (prediabetes). This enables a more precise assessment of the risk of developing diabetes.
Three of the newly identified subtypes are characterized by a low risk of diabetes, three by an increased risk. People who belong to the high-risk subtypes are more likely to develop type 2 diabetes, fatty liver or damage to the kidneys and cardiovascular system. A new study argues in favor of remission of prediabetes as a therapeutic goal, i.e., a reduction in symptoms. This approach protects against the development of type 2 diabetes and leads to improved kidney and vascular function in the long term.

Translational Research Successes: Subtypes of Prediabetes Discovered

Preventing diabetes (diabinfo.de)

Subtypes of Type 2 Diabetes

Analyses of large clinical studies, including the German Diabetes Study by the DZD, have identified five subtypes of diabetes. Depending on the subtype, the risk of developing complications such as fatty liver and damage to the eyes, nerves or kidneys varies in people with diabetes.  With the help of mathematical formulas, routinely collected variables can be used to find out which people produce less insulin, are prone to high blood pressure or lipid metabolism disorders, or develop specific complications of diabetes within the first five years after they have been diagnosed with diabetes. These research findings have the potential to change the way type 2 diabetes is understood and treated and make it possible to enter the world of precision diabetology.  

Translational Research Successes: Treating Diabetes More Precisely

Subtypes of Diabetes in Children and Adolescents 

There are also different subtypes of diabetes in children and adolescents. A study with DZD participation identified ten different subgroups of diabetes in young people, including seven groups of children with type 1 diabetes (autoimmune diseases) with certain antibodies in the blood, and three groups without these antibodies. The new findings could enable more precise diabetes prognosis and therapy in the future.

Research news: Diabetes in Childhood and Adolescence – Different Subgroups Identified