History and exam

Key diagnostic factors

Random plasma glucose ≥11.1 mmol/L (≥200 mg/dL). A typical presenting feature.[37][35]

Getting up at night to urinate is typical.[35]

Getting up at night to drink water is typical.[35]

Other diagnostic factors

Usually presents in childhood or adolescence with the highest incidence observed in children aged 10-14 years, but can occur at any age.[13]

Weight loss occurs at onset; often rapid in adults.[37][35]

Occurs with high or fluctuating blood sugar levels.

Suggest diabetic ketoacidosis. See our topic Diabetic ketoacidosis.

Suggests diabetic ketoacidosis. See our topic Diabetic ketoacidosis.

Suggests diabetic ketoacidosis. See our topic Diabetic ketoacidosis.

Suggests diabetic ketoacidosis. See our topic Diabetic ketoacidosis.

Suggests diabetic ketoacidosis. See our topic Diabetic ketoacidosis.

Excessive tiredness is a typical presenting feature in children in particular.[35]

May suggest diabetic ketoacidosis. See our topic Diabetic ketoacidosis.

Suggests diabetic ketoacidosis. See our topic Diabetic ketoacidosis.

Risk factors

Over 50 genetic loci associated with type 1 diabetes risk have been identified.[15][31] Genetic variation in the HLA region (involved in the immune response), accounts for a large proportion, with HLA DR4-DQ8 and HLA DR3-DQ2 conferring the highest risk.[15][14]

The risk of type 1 diabetes in children with an affected family member is 5% (compared to a risk of 0.3% in children without an affected family member).[14] In one study, concordance for type 1 diabetes was 27.3% in monozygotic twins and 3.8% in dizygotic twins.[32]

In genetically susceptible individuals, environmental factors may trigger the immune-mediated destruction of pancreatic beta cells.[15]

There is significant geographical variation in the incidence of type 1 diabetes, and it is more common in European people and less common in Asian people.[7] Human leukocyte antigen (HLA) risk profile for type 1 diabetes is widening over time, which may reflect increased environmental influence on susceptible genotypes.[33] Regional variation suggests different contributing risk exposures.[15]

Strongest evidence to date is for human enteroviruses.[16][17][18]

Among dietary factors, supplementation with vitamin D may be protective.[19][20] Further research is required to determine the effect of cow's milk, early introduction of cereals, or maternal vitamin D ingestion on type 1 diabetes risk.[21][22][23] There is no consensus about the effect of breastfeeding on risk for type 1 diabetes.[34]

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