Investigations

1st investigations to order

urine dipstick

Test
Result
Test

Glycosuria is present in most children with type 2 diabetes mellitus (T2DM); absence of accompanying ketonuria suggests, but does not prove, T2DM as opposed to type 1 diabetes mellitus.

Result

glycosuria

random plasma glucose

Test
Result
Test

Confirms diagnosis in the presence of symptoms of hyperglycaemia (e.g., polyuria, polydipsia, and unexplained weight loss) or hyperglycaemic crisis.[1]​​

Result

≥11.1 mmol/L (≥200 mg/dL)

fasting plasma glucose

Test
Result
Test

Order after a minimum 8-hour fast.[1]​ ​In the absence of unequivocal hyperglycaemia, confirm an elevated result with an HbA1c (which can be done on the same sample), a second fasting plasma glucose, or another diabetes diagnostic test.[1]​​

Result

≥7 mmol/L (≥126 mg/dL)

HbA1c

Test
Result
Test

In the absence of unequivocal hyperglycaemia, confirm with a repeat HbA1c or another diabetes diagnostic test.[1]​​

HbA1c reflects degree of hyperglycaemia over the preceding 3 months.[1]​​

Result

≥48 mmol/mol (6.5%)

autoantibodies to insulin, islet cells, islet antigens, glutamic acid decarboxylase, and zinc transporter 8

Test
Result
Test

Children and adolescents with overweight or obesity in whom a diagnosis of type 2 diabetes is being considered should have these pancreatic autoantibodies tested to exclude a diagnosis of type 1 diabetes.[1]​​

Results of pancreatic autoantibody testing may not always be available at the initiation of treatment. Treatment will need to be adjusted if patients are positive for pancreatic autoantibodies and a diagnosis of type 1 diabetes is confirmed. For more information, see Type 1 Diabetes.

Result

typically negative

Investigations to consider

2-hour plasma glucose

Test
Result
Test

Plasma glucose is measured 2 hours after 75 g oral glucose load.[1]​​

Patients should be advised to consume a varied diet with at least 150 g of carbohydrate on the 3 days prior to testing, as fasting and carbohydrate restriction can falsely increase plasma glucose levels.[1]​​

Result

≥11.1 mmol/L (≥200 mg/dL)

random C-peptide

Test
Result
Test

Not done routinely for diagnosis of diabetes, but may be useful in differentiating between type 1 and type 2 diabetes.[55]

Absolute insulin deficiency is a key feature of type 1 diabetes, which results in low (<0.2 nanomol/L) or undetectable levels of plasma C-peptide.[55]

C-peptide results must be interpreted in the clinical context of disease duration, comorbidities, and family history.[55]

Although C-peptide can be helpful in evaluating the endogenous production of insulin, both type 1 and type 2 diabetes can be associated with insulinopenia, and endogenous insulin production can be detected in some individuals with type 1 diabetes for prolonged periods of time after diagnosis.

Result

>1 nanomol/L

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