Investigations
1st investigations to order
random plasma glucose
Test
Hyperglycaemia in hospitalised patients is defined as blood glucose >7.8 mmol/L (>140 mg/dL).[1]
Clinically significant hypoglycaemia is defined as glucose levels <3.9 mmol/L (<70 mg/dL), regardless of the presence or severity of acute symptoms.[1]
A random plasma glucose of ≥11.1 mmol/L (≥200 mg/dL) accompanied by symptoms of hyperglycaemia (polyuria, polydipsia, weight loss) or hyperglycaemic crisis confirms a diagnosis of diabetes.[1]
Result
hyperglycaemia in hospitalised patients: blood glucose >7.8 mmol/L (>140 mg/dL); level 1 hypoglycaemia: blood glucose <3.9 mmol/L (<70 mg/dL) and ≥3.0 mmol/L (≥54 mg/dL); level 2 hypoglycaemia: blood glucose <3.0 mmol/L (<54 mg/dL); level 3 hypoglycaemia: severe event characterised by altered mental and/or physical status requiring assistance for treatment of hypoglycaemia
HbA1c
Test
HbA1c ≥48 mmol/mol (≥6.5%) on two separate occasions, or a single HbA1c ≥48 mmol/mol (≥6.5%) in combination with either a fasting glucose ≥7 mmol/L (≥126 mg/dL) or a random plasma glucose of ≥11.1 mmol/L (≥200 mg/dL), is diagnostic of diabetes.[1]
The oral glucose tolerance test is not usually done during hospitalisation. HbA1c may be useful in differentiating previously unrecognised diabetes from transient hyperglycaemia. A normal HbA1c in the face of new hyperglycaemia suggests transient hyperglycaemia, while a raised HbA1c suggests long-standing diabetes. HbA1c can also help assess prior treatment and control of known diabetes.[1]
Result
≥48 mmol/mol (≥6.5%) suggests chronic hyperglycaemia; elevated HbA1c must be confirmed on a separate occasion for diagnosis of diabetes
serum urea, creatinine, and eGFR
Test
Renal insufficiency is a risk factor for hypoglycaemia.
Result
may be abnormal in diabetic nephropathy
spot urine albumin/creatinine ratio (ACR)
Test
Normal to mildly increased: ACR <30 mg/g; moderately increased (formerly microalbuminuria): ACR 30-299 mg/g; severely increased (formerly macroalbuminuria): ACR ≥300 mg/g.[1]
Result
may be abnormal in diabetic nephropathy
serum ketones
Test
Serum ketone levels should be interpreted in the context of the clinical picture, as elevations can occur in conditions such as starvation.
Beta-hydroxybutyrate is considered raised when levels exceed 300 micromol/L (3 mg/dL).
Urine ketone testing is not recommended as it may reflect ketone levels from several hours earlier, limiting its usefulness in acute assessment.
Result
may be positive
Investigations to consider
post-discharge fasting plasma glucose or HbA1c
Test
All patients admitted to hospital with new-onset hyperglycaemia should be assessed for the presence of diabetes with a post-discharge fasting glucose or HbA1c.
Abnormal results need to be confirmed on a separate day.
Result
≥7 mmol/L (≥126 mg/dL) or HbA1c ≥48 mmol/mol (≥6.5%) is diagnostic of diabetes mellitus
post-discharge 2-hour post-load glucose after 75 g oral glucose (oral glucose tolerance test)
Test
All patients admitted to hospital with new-onset hyperglycaemia should be assessed for the presence of diabetes with a follow-up test. Testing 2-hour post-load glucose after 75 g oral glucose may be needed when diabetes is strongly suspected post-discharge, but fasting plasma glucose (<7 mmol/L [<126 mg/dL]) or HbA1c is not diagnostic. 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]
Abnormal results need to be confirmed on a separate day.
Result
2-hour plasma glucose ≥11.1 mmol/L (≥200 mg/dL) is diagnostic of diabetes mellitus
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