Glucose Tolerance Testing - Mayo Medical Laboratories

Porter Medical Center Laboratory115 Porter DriveMiddlebury, VT 05753Oral Glucose Tolerance Test [Non-Gestational]Diabetes Mellitus is a metabolic disease characterized by insufficient insulin secretion or increased cellular resistanceto insulin. Fasting glucose is the recommended screening test; however, a glucose challenge may be neededto confirm the diagnosis. Many other conditions can cause hyperglycemia so patients should be ambulatory andotherwise healthy to ensure meaningful results.ProtocolPatients should be instructed to maintain normal activity and to consume a diet, which provides at least 150 gramsof carbohydrate per day three days prior to testing. If possible all medications should be discontinued. Testingshould be performed in the morning after a 10 to 12 hour fast (water is allowed). This test is not appropriate forthe inpatient population.Non-pregnant Adults: 2-hour glucose tolerance test.1. Collect a fasting blood sample in gray top tube. A urine sample is unnecessary.2. Give 75-gram dose of Glucola (10 fl. oz.).3. Collect blood glucose sample at 2 hours. Collect in gray top tube.4. LABEL BOTH SAMPLES WITH TIME OF COLLECTION.Children: 2-hour glucose tolerance test.1. Collect a fasting blood sample in gray top tube. A urine sample is unnecessary2. Give glucose dose of 0.8 gram of glucose per lb. body weight (1.75 g/kg ideal weight) to a maximum of75 grams. Children weighing more than 95 lbs receive 75 grams of glucose. Refer to the chart.3. Collect blood glucose sample 2 hours. Collect in gray top tube.4. LABEL BOTH SAMPLES WITH TIME OF COLLECTION.Reference RangesFasting plasmaglucoseNormal Impaired Fasting Glucose Diabetes Mellitus 110 mg/dl and < 126 mg/dl> or = 126 mg/dl withclassic symptomsRandom plasma> or = 200 mg/dl with

Porter Medical Center Laboratory115 Porter DriveMiddlebury, VT 05753Interpretation: Criteria for diagnosis according to the American Diabetes Association, revised 1997.Diabetes Mellitus (Non-Gestational): The diagnosis may be made by any of the following three findings.All findings must be confirmed by documenting any one of the three findings on a subsequent day.1. Fasting plasma glucose > or = 126 mg/dl, confirmed by repeat testing.2. Random plasma glucose >or = 200 mg/dl and classic symptoms (polydipsia, polyuria, and weightloss).3. Oral glucose tolerance test with 2-hour plasma glucose > or = 200 mg/dl.Impaired Fasting Glucose1. Fasting glucose > or = 110 mg/dl and less than 126 mg/dl.OR2. Two-hour oral glucose tolerance test with 2-hour glucose > or = 140 mg/dl but < 200 mg/dl.ORAL GLUCOSE TOLERANCE TEST DOSAGE CHARTPatients receive a glucose dose of 75 grams for adults (1.75 gram/kg body weight or 0.8 grams/lb. body weight).Patients weighing more than 95 lbs. receive 75 grams of glucose (10 fl. oz.)WEIGHT WEIGHT IN KG GLUCOSE IN GMS GLUCOSE IN Fl. Oz DOSE IN CC (ml) DISCARD CC (ml)IN LBS95 43 75 10 300 090 41 72 9.6 288 1285 38 68 9.1 273 2780 36 64 8.5 255 4575 34 60 8.0 240 6070 32 56 7.4 222 7865 30 52 6.9 207 9360 27 48 6.4 192 10855 25 44 5.9 177 12350 23 40 5.3 159 14145 20 36 4.8 144 15640 18 32 4.3 129 17135 16 28 3.7 111 18930 14 24 3.2 96 20425 12 20 2.7 81 21920 9 16 2.1 63 23715 7 12 1.6 48 25210 5 8 1.0 30 270References1. Oral Glucose Tolerance Test (Non-Gestational), Prepared by Mary E. Tang, M.D., FAHC LaboratoryServices Directory, December 2004.Glucose Tolerance Testing (Non-gestational) - 2 - JUNE 2013