Hypoglycemia and Glucose Tolerance Test Quiz

Glucose Measurement

• Hypoglycemia in adults is defined as a glucose level below 70 mg/dL (3.9 mmol/L) after an overnight fast.
• In the given patient, whole blood glucose is 77 mg/dL (4.2 mmol/L), serum blood glucose is 88 mg/dL (4.8 mmol/L), and CSF glucose is 56 mg/dL (3.1 mmol/L).

Glucose Tolerance Testing

• Preparation for standard glucose tolerance testing includes overnight fasting.
• A fasting glucose of 90 mg/dL (5 mmol/L) would correspond to a 2-hour postprandial glucose result of around 140 mg/dL (7.8 mmol/L) for normal glucose metabolism.

Cerebrospinal Fluid (CSF) Glucose

• A healthy person with a blood glucose of 80 mg/dL (4.4 mmol/L) would have a CSF glucose value of around 60-70 mg/dL (3.3-3.9 mmol/L).
• CSF for glucose assay should be collected in a fluoride-containing tube to inhibit glycolysis.

Oral Glucose Tolerance Test (OGTT)

• If a patient becomes nauseated and vomits 90 minutes after receiving a standard 75 g carbohydrate dose for an OGTT, the test should be stopped and restarted at a later time.

Diabetes Diagnosis

• A 2-hour postprandial glucose value of 200 mg/dL (11.1 mmol/L) or higher demonstrates unequivocal hyperglycemia diagnostic for diabetes mellitus.

Hypoglycemia in Infants

• Serum levels that define hypoglycemia in pre-term or low birth weight infants are below 40 mg/dL (2.2 mmol/L).

Glucose Concentrations

• A fasting serum glucose concentration of 95 mg/dL (5.2 mmol/L) is considered impaired fasting glucose.
• Pregnant women with symptoms of thirst, frequent urination, or unexplained weight loss should have a 2-hour OGTT performed.

Blood Glucose Variations

• In the fasting state, arterial and capillary blood glucose concentrations vary from venous glucose concentration by approximately 5-10 mg/dL (0.3-0.6 mmol/L).

Glycolysis

• The conversion of glucose or other hexoses into lactate or pyruvate is called glycolysis.