Clinical Significance

   A 2-hour post-prandial blood sugar (glucose) test measures the blood sugar exactly 2 hours after the start of a meal. It is useful for diagnosing and managing diabetes mellitus and other carbohydrate metabolism disorders including gestational diabetes, neonatal hypoglycemia, idiopathic hypoglycemia, and pancreatic islet cell carcinoma.

Specimen

   Serum

Stability

   Refrigerated (preferred) : 7 days

   Frozen : 30 days

Reference Range

   65 – 180 mg/dL

Interpretation

   Any of the following results, confirmed on a subsequent day, can be considered diagnostic for diabetes: Fasting plasma or serum glucose ≥ 126 mg/dL after an 8-hour fast, 2-Hour plasma or serum glucose ≥ 200 mg/ dL during a 75-gram oral glucose tolerance test (OGTT), Random glucose >200 mg/dL, plus typical symptoms.

   Patients with "impaired" glucose regulation are those whose fasting serum or plasma glucose fall between 101 and 126 mg/dL, or whose 2-hour value on oral glucose tolerance test fall between 140 and 199 mg/dL. These patients have a markedly increased risk of developing type 2 diabetes and should be counseled for lifestyle changes and followed up with more testing. Indications for screening and testing include strong family history, marked obesity, history of babies over 9 pounds, and recurrent skin and genitourinary infections.

   Glucose levels of 25 mg/dL or lower in infants younger than 1 week are considered to be potentially life threatening, as are glucose levels of 40 mg/dL or lower in infants older than 1 week. Glucose levels of 400 mg/dL and higher are considered a critical value.

Limitation

   At ambient temperature, the glucose concentration in the blood will decrease by 10% per hour. Therefore, in a nongel separator tube, the specimen should be centrifuged as soon as possible and the plasma or serum removed from the cells. If the blood is drawn in a serum separator tube (SST) or plasma separator tube (PST), the glucose is stable once the specimen has been spun and the gel is in place.