Diabetes classification

Author: Dr Sorin Ioacara | Last update: November 9th, 2020

A tree with lots of branches

Discover here: Suspicions for other types of diabetes | Main diabetes types | Type 1 diabetes | Type 2 diabetes | Secondary diabetes | Gestational diabetes

A correct classification of the form of diabetes offers the chance of a more effective treatment. The classification of diabetes poses more significant problems compared to its diagnosis. For example, diabetes mellitus with onset in the first six months is in over 99.9% other forms of diabetes besides the classic type 1 diabetes. That is why it has been called neonatal diabetes.

Diabetes in children with onset after the age of six months is type 1 diabetes in more than 50% of cases. When there are doubts about the correctness of type 1 diabetes diagnosis, it is a good idea to consult a centre experienced in rare forms of diabetes.

When should you suspect other types of diabetes than the classic ones?

An infant with a toy in his mouth suggesting neonatal diabetes

Diagnosing diabetes is not always easy. And the hardship is just beginning. It may not be possible to pinpoint on spot the exact form of diabetes the patient is suffering from. However, tracking the course of diabetes will, in many cases, elucidate the precise subtype of the disease. You should suspect another type of diabetes in any child with absent type 1 diabetes antibodies and at least one of the following conditions:

  • Family history of monogenic diabetes (e.g. MODY)
  • Onset before the age of 12 months (less than six months is for sure not type 1 diabetes)
  • Fasting blood glucose in the morning <150 mg/dl (8.3 mmol/l) in a normal-weight child without symptoms
  • Transient remission lasting more than one year
  • Required insulin <0.5 U/kg body weight more than one year after onset
  • The association of other severe conditions such as deafness or optic atrophy.
  • Exposure to drugs that can affect the endocrine pancreas: immunosuppressants, glucocorticoids, some antidepressants

The main types of diabetes

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There are four broad categories of diabetes. For an experienced diabetologist, however, there are several hundred small categories of diabetes. The immediate consequence of a correct inclusion in one of these hundreds of mini-categories is receiving a more precise treatment. The following is a brief presentation of the main categories of diabetes. You can find detailed information in their dedicated chapters.

The primary forms of diabetes are the following:

  1. Type 1 diabetes
  2. Type 2 diabetes
  3. Secondary diabetes mellitus (other specific types)
    • Monogenic diabetes affecting insulin secretion
    • Genetic defects in insulin action
    • Diseases of the exocrine pancreas
    • Endocrine diseases
    • Drugs and toxic substances
    • Infections
    • Rare forms of autoimmune diabetes
    • Complex genetic syndromes
  4. Gestational diabetes

Type 1 diabetes mellitus

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Type 1 diabetes mellitus has a dedicated chapter. It is an autoimmune endocrine disorder characterized by the almost total removal of pancreatic beta cells by the immune system. In some cases of type 1 diabetes, doctors cannot demonstrate the autoimmunity, at least using current technical means. In these situations, type 1 diabetes is idiopathic, i.e. of unknown origin. Without treatment, the spontaneous evolution is towards diabetic ketoacidosis.

Type 2 diabetes mellitus

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Type 2 diabetes is an endocrine disorder characterized by a significant reduction in the ability of the pancreas to secrete the entire amount of insulin required by the body. A substantial resistance to the action of insulin always accompanies type 2 diabetes in children. The cause of this form of diabetes is a combination of genetic factors, sedentary lifestyle and overeating (especially fat).

Secondary diabetes

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Secondary diabetes mellitus has a dedicated chapter. A synonym for it would be other specific types of diabetes. This broad group of diabetes subtypes, all have in common that doctors know the primary cause that led to diabetes. For this reason, in many cases, there is a distinct therapeutic solution, much more useful than the standard one.

Gestational diabetes

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Gestational diabetes is a form of diabetes that has the peculiarity that you discover it in the 2nd or 3rd trimester of pregnancy. Diabetes found in the first trimester of pregnancy is not gestational diabetes, but type 1, type 2 or secondary diabetes. It often pre-existed before pregnancy. The diagnosis of gestational diabetes automatically disappears at birth, but may recur in a future pregnancy.


  1. American Diabetes Association Guideline 2020
  2. ISPAD Clinical Practice Consensus Guidelines 2018
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