Tests
1st tests to order
random plasma glucose
Test
Hyperglycemia in hospitalized patients is defined as blood glucose >140 mg/dL (>7.8 mmol/L).[1] Glucose levels <70 mg/dL (<3.9 mmol/L) are considered clinically important hypoglycemic events independent of the severity of acute hypoglycemic symptoms.[1]
As a diagnostic screening test, random plasma glucose of ≥200 mg/dL (≥11.1 mmol/L) accompanied by symptoms of hyperglycemia (polyuria, polydipsia, weight loss) or hyperglycemic crisis confirms a diagnosis of diabetes.[1]
Result
hyperglycemia in hospitalized patients: blood glucose >140 mg/dL (>7.8 mmol/L); level 1 hypoglycemia: blood glucose <70 mg/dL (<3.9 mmol/L) and ≥54 mg/dL (≥3.0 mmol/L); level 2 hypoglycemia: blood glucose <54 mg/dL (<3.0 mmol/L); level 3 hypoglycemia: severe event characterized by altered mental and/or physical status requiring assistance for treatment of hypoglycemia
HbA1c
Test
HbA1c ≥6.5% (≥48 mmol/mol) on two separate occasions, or a single HbA1c ≥6.5% (≥48 mmol/mol) in combination with either a fasting glucose ≥126 mg/dL (≥7.0 mmol/L) or a random plasma glucose of ≥200 mg/dL (≥11.1 mmol/L), is diagnostic of diabetes.[1]
The oral glucose tolerance test is not usually done during hospitalization. HbA1c may be useful in differentiating previously unrecognized diabetes from transient hyperglycemia. A normal HbA1c in the face of new hyperglycemia suggests transient hyperglycemia, while an elevated level suggests long-standing diabetes. HbA1c can also help assess prior treatment and control of known diabetes.[1]
Result
≥6.5% (≥48 mmol/mol) suggests chronic hyperglycemia; elevated HbA1c must be confirmed on a separate occasion
serum BUN, creatinine, and eGFR
Test
Renal insufficiency is a risk factor for hypoglycemia.
Result
may be abnormal in diabetic nephropathy
spot urine albumin/creatinine ratio
Test
Microalbuminuria has historically been defined as 30-299 micrograms/mg creatinine.
Macroalbuminuria has historically been defined as ≥300 micrograms/mg creatinine.
Result
<30 micrograms/mg creatinine is normal and excludes diabetic nephropathy
serum ketones
Test
Need to correlate with clinical picture, because serum ketones may be elevated in starvation.
Beta-hydroxybutyrate is elevated when >3 mg/dL (>300 micromol/L).
Urine ketones are not recommended as they may reflect the patient's state several hours ago.
Result
may be positive
Tests to consider
post-discharge fasting plasma glucose or HbA1c
Test
All patients admitted to the hospital with new-onset hyperglycemia 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
≥126 mg/dL (≥7.0 mmol/L) or HbA1c ≥6.5% (≥48 mmol/mol) is diagnostic of diabetes mellitus
post-discharge 2-hour postload glucose after 75 g oral glucose
Test
All patients admitted to the hospital with new-onset hyperglycemia should be assessed for the presence of diabetes with a follow-up test. Testing 2-hour postload glucose after 75 g oral glucose may be needed when diabetes is strongly suspected post-discharge, but fasting plasma glucose (<126 mg/dL [<7.0 mmol/L]) 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 ≥200 mg/dL (≥11.1 mmol/L) is diagnostic of diabetes mellitus
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