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Glucose, plasma, serum

Glucose levels in serum and plasma are used to diagnose and monitor therapy in diabetes. Three main tests are used for the diagnosis of diabetes according to the American Diabetic Association:

  1. Fasting plasma glucose
  2. Random plasma glucose test
  3. Two hours post-glucose load.


Immunoassay, high performance liquid chromatography.

Reference levels

Fasting blood glucose

  1. Symptoms of diabetes plus a fasting plasma glucose level of 126 mg/dL on two occasions after an 8 hour fast.

  2. If the measurement is between 110 and 126 this is impaired fasting glucose.  An oral glucose tolerance test should be performed. It is reserved for patients without symptoms in which fasting glucose test is nondiagnostic. It should be done after an overnight fast. Results are valid only when the patient is not under stress and physical activity is unrestricted and daily carbohydrate intake is more than 150g/dL.

Random blood glucose

  1. A random plasma glucose of 200 mg /dL or greater denotes diabetes.

2-hour postprandial blood sugar (2-hour PP)

  1. This is a measurement of blood glucose done exactly 2 hours after taking a meal.

  2. Between 140 mg/dL to 200 mg/dL glucose level denotes impaired glucose tolerance. Whilst this condition is asymptomatic it carries an increased risk of large vessel disease.

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