Classification of Diabetes


There are many different types of diabetes resulting from various causes. The tables below provide a classification by aetioloigy (cause).

Classification of Diabetes Mellitus

Type 1 Diabetes (T1DM)

  • Type 1A
    Immune mediated
  • Type 1B
Type 1 diabetes accounts for 5-10% of cases, and results from the destruction of insulin-producing beta-cells in the pancreas. It usually results in absolute insulin deficiency.

Therapy requires insulin replacement by injection or insulin pump.

Type 2 Diabetes (T2DM) Type 2 diabetes is the ‘diabetes’ that is currently a Hot Topic frequently featured in the news and media. Type 2 diabetes accounts for up to 95% of cases.

It may be essentially insulin resistance with relative insulin deficiency, or may be predominantly an insulin secretory defect with accompanying insulin resistance… or it may be something inbetween…

Therapy ranges from lifestyle changes through to close dietary management, daily medication, and often, eventually insulin replacement.

Other Specific Types

  • Genetic defects of beta-cell function (MODY)
  • Genetic defects in insulin action
  • Diseases of the exocrine pancreas
  • Endocrinopathies
  • Drug-induced or Chemical-induced
  • Infections
  • Uncommon forms of immune-mediated diabetes
  • Other genetic syndromes

MODY has proven to be a useful tool for the invetigation of potential new therapies for Type 2 diabetes.


This group embraces the majority of diabetes for which a specific cause is either definitely known (or sometimes definitely not known (!))


Therapy is usually dictated by the degree of insulin insufficiency.


Gestational Diabetes (GDM) Defined as: Any degree of glucose intolerance that is discovered during pregnancy. Reflecting the ratio of Type 2 to Type 1 diabetes, GDM represents nearly 90% of pregnancies complicated by diabetes.

Therapy is determined by immediate blood glucose levels.


Diabetes is a disorder characterised by a higher than normal blood glucose (sugar) level (hyperglycaemia). Blood glucose levels are normally controlled by the hormone insulin; this is produced by beta cells in the pancreas (a gland which lies just below the stomach).

Glucose, from the sugars and starches that we eat, is transported in the bloodstream. Insulin is needed for glucose to leave the bloodstream and enter the body’s cells where it is burned to provide energy. Without insulin, cells are deprived of glucose and energy, and the blood glucose level rises.


Classification of Diabetes Mellitus

– Other Specific Types/Causes


Genetic defects of beta-cell function (MODY)

  • MODY1
  • MODY2
  • MODY3
  • MODY4
  • MODY5
  • MODY6
  • Mitochondrial DNA

>> more detailed information on MODY subtypes

Genetic defects in insulin action

  • Type A insulin resistance
  • Leprechaunism
  • Rabson-Mendenhall syndrome
  • Lipoatrophic diabetes

Diseases of the exocrine pancreas

  • Pancreatitis
  • Trauma / pancreatectomy
  • Neoplasia
  • Cystic fibrosis
  • Haemochromotosis
  • Fibrocalculus pancreatopathy


  • Acromegaly
  • Cushing’s syndrome
  • Glucagonoma
  • Phaeochromocytoma
  • Hyperthyroidism
  • Somatostatinoma
  • Aldosteronoma

Drug / chemical-induced

  • Vacor
  • Pentamidine
  • Nicotinic acid
  • Glucocorticoids
  • Thyroid hormone
  • Diazoxide
  • beta-Adrenergic agonists
  • Thiazides
  • Dilantin
  • alpha-Interferon


  • Congenital rubella
  • Cytomegalovirus

Uncommon forms of immune-mediated diabetes

  • “Stiff-man” syndrome
  • Anti-insulin receptor antibodies

Other genetic syndromes

  • Down’s syndrome
  • Klinefelter’s syndrome
  • Turner’s syndrome
  • Wolfram’s syndrome
  • Friedreich’s ataxia
  • Huntingdon’s chorea
  • Laurence-Moon-Biedl syndrome
  • Myotonic dystrophy
  • Porphyria
  • Prader-Willi syndrome


American Diabetes Association