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Classification of Diabetes

    Type 1 Diabetes. This is due to ß-cell destruction leading to an absolute deficiency of insulin. It is usually acute in onset and requires obligatory treatment with insulin to percent life threatening ketoacidosis coma. It accounts for 10% or less of all diabetes.

    Type 2 Diabetes. This is due to an imbalance between insulin secretion and insulin action. It is often insidious in onset and may have been present a number of years before diagnosis. It accounts for 90% or more of all diabetes.

    Type 3 Diabetes. This is a group of disorders, many of genetic origin, that lead to or are associated with diabetes. In particular Type 3A is an autosomal dominant genetic defect in ß-cell function characterised by onset at an early age. They were previously referred to as maturity-onset diabetes of the young (MODY). They include HNF-1ß, glucokinase and less commonly HNF-4ß, HNF-1ß, insulin promoter factor (IPF)-1 and NeuroD1 gene defects. They should be considered in those diagnosed aged <30 years with a strong family history of diabetes extending over 3 generations. The various types are: A Genetic defects of ß-cell function; B Genetic defects of insulin action; C Diseases of the exocrine pancreas; D Endocrinopathies; E Drug induced; F Infections; G Other immune mediated; H Other genetic syndromes associated with diabetes.

    Type 4 Diabetes/ Gestational Diabetes Mellitus. This is a glucose intolerance found in pregnancy and documented to revert back to normal after delivery. It usually recurs in subsequent pregnancies and there is a high future risk of diabetes in the mother.

    Categorisation of diabetes can thus usually be done on clinical grounds and with observation of the natural history. Only when there is sufficient uncertainty to have significant impact on the management plan is further more detailed investigation warranted.

    General Classification of Diabetes

    Type 1

    Remember, these statements are generalities

    Type 2


    Either can occur at almost any age


    Rapid onset

    Either can be slow or rapid in onset

    Slow onset


    Truly asymptomatic T2DM is unusual


    Weight loss

    No all T2DM patients are obese and many lose weight at diagnosis


    Ketonuria + ve

    Urine ketones must be tested for

    Ketonuria - ve

    Ketoacidosis likely

    T2DM can still get hyperglycaemic coma e.g. HONK


    Insulin mandatory

    Many patients with T2DM are insulin treated.

    Insulin maybe