History and exam

Key diagnostic factors

common

hyperglycaemia

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

polyuria

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

polydipsia

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

Other diagnostic factors

common

young age

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

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

blurred vision

Occurs with high or fluctuating blood sugar levels.

nausea and vomiting

Suggest diabetic ketoacidosis. See our topic Diabetic ketoacidosis.

abdominal pain

Suggests diabetic ketoacidosis. See our topic Diabetic ketoacidosis.

clinical dehydration

Suggests diabetic ketoacidosis. See our topic Diabetic ketoacidosis.

abdominal pain

Suggests diabetic ketoacidosis. See our topic Diabetic ketoacidosis.

tachypnoea

Suggests diabetic ketoacidosis. See our topic Diabetic ketoacidosis.

lethargy

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

May suggest diabetic ketoacidosis. See our topic Diabetic ketoacidosis.

uncommon

coma or altered mental status

Suggests diabetic ketoacidosis. See our topic Diabetic ketoacidosis.

Risk factors

strong

genetic predisposition

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]

weak

geographical region

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]

infectious agents

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

dietary factors

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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