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2 Hour, 75 gram Glucose Tolerance Test, Non-pregnancy

Item Value
Approval req'd? No
Available Stat? No
Utilization Guidelines THIS TEST IS NO LONGER RECOMMENDED FOR ROUTINE USE.

See Additional Information.
Test code OGT, GT120
Test group Glucose
Performed by Parnassus & Mt. Zion Chemistry
In House Availability Test available 24 hours per day 7 days per week
Method Oxygen consumption (O2 electrode with glucose oxidase)
Patient Preparation The patient should be instructed by the care-giver to eat a normal diet containing at least 150 g of carbohydrate and carry out normal physical activity for at least 3 days prior to the morning of the test. An 8-14 hour fast is required before initial baseline sample collection.
Collection Instructions For outpatients, PLEASE SCHEDULE IN ADVANCE with the ACC outpatient lab, 415-353-2736, or Post St. lab, 415-885-7531. Outpatient testing at ACC available 0730-1530 weekdays, and at 2330 Post St. 0800-1400 weekdays.

The patient should be seated for the test and should not smoke.

A gray top tube should be used.

For patients < 18 years of age, obtain the patient's weight and give the patient 1.75 g of glucose per kg of body weight. If the weight is in pounds, divide by 2.2 to get kg. Do not provide more than 75 g dose regardless of body weight.
Container type Gray top
Amount to Collect 1 mL blood Click here for Microdetermination info
Sample type Serum
Preferred volume 0.5 mL serum
Min. Volume 0.2 mL serum Click here for Microdetermination info
Units mg/dL
Normal range
Fasting 70-99 mg/dL
Normal < 140 mg/dL
Impaired glucose tolerance 140-199 mg/dL
Diabetes mellitus > 199 mg/dL*


* If confirmed on another day by repeat OGT, or a diagnostic elevation of the fasting or non-fasting glucose.
Synonyms Diabetes mellitus
Stability Room temperature 8 hours, refrigerated 2 days
Additional information Based on 75 g dose ingested over 5 minutes.

THIS TEST IS NO LONGER RECOMMENDED FOR ROUTINE USE.

When performed it is abbreviated to a single 2 hour post-glucose specimen.

All patients should be screened with a fasting glucose: Do not perform this test if the fasting glucose exceeds 125!

90% of patients whose 2 hour level is > 199 mg/dL have fasting hyperglycemia, obviating the need for tolerance testing.

Reference values from position statement of the American Diabetes Association on Diagnosis and Classification of Diabetes (Diabetes Care, Volume 34, Supplement 1, January 2011).
Last Updated 10/21/2014 11:51:55 AM
Entry Number 1030
Lab Procedure Link Click here for Procedure
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