Investigations

1st investigations to order

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Confirms diagnosis in the presence of symptoms of polyuria, polydipsia, and unexplained weight loss.[1]

Result

≥11 mmol/L (≥200 mg/dL)

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Fasting is defined as no caloric intake for at least 8 hours.

Result

≥6.9 mmol/L (≥126 mg/dL)

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Plasma glucose is measured 2 hours after 75 g oral glucose load.

Result

≥11 mmol/L (≥200 mg/dL)

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In the presence of hyperglycaemia suggest type 1 diabetes.

Result

medium or high quantity

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Reflects degree of hyperglycaemia over the preceding 3 months.

Result

≥48 mmol/mol (≥6.5%)

Investigations to consider

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C-peptide is a byproduct formed when pro-insulin is processed to insulin. Therefore, its levels reflect insulin production. Half life of C-peptide is 3 to 4 times longer than that of insulin.

Low or undetectable C-peptide level indicates absence of insulin secretion from pancreatic beta cells.

Result

low or undetectable

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These include autoantibodies to glutamic acid decarboxylase, insulin, islet cells, islet antigens (IA2 and IA2-beta), and the zinc transporter ZnT8.

Presence indicates autoimmune beta-cell destruction.

Result

positive

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