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Glucose Tolderance, 2hr Post dose (non-OB)
Test CodeGTT2H (cs) - NOCO
Alias/See Also
Includes:
GLUC F (GTT)
GLUC 2 (GTT)
GLUC F (GTT)
GLUC 2 (GTT)
CPT Codes
82951
Preferred Specimen
1.0 mL plasma from Green top (Lithium Heparin)
Minimum Volume
0.5 mL
Other Acceptable Specimens
1.0 mL serum from Serum Gel or Red Top
Instructions
A copy of the Glucose Tolerance Patient Information should be given to the outpatient.
- Draw blood early in morning from a patient fasting at least 8 hours.
- Perform glucose monitor from green-top (LiHep) tube or on a fingerstick specimen before giving patient 75 g GlucolaTM supplied.
- For outpatients drawn at an NCMC service center: If fasting glucose monitor or fingerstick glucose is >120 mg/dL, notify North Colorado Medical Center Chemistry Department at 970-810-6412 and forward fasting tube for a STAT Glucose. If this value is >120 mg/dL, do not proceed with procedure. Chemistry department will notify a pathologist, and he will contact patient’s physician. Patient will be asked to wait (if outpatient) until physician can be contacted.
- For patients drawn at remote clinics: A fasting glucose monitor or fingerstick glucose is >120 mg/dL is diagnostic of diabetes mellitus. However, finger stick glucose value is not as accurate as confirmatory glucose value from a standard chemistry analyzer. Therefore, dependent on the magnitude of finger stick glucose value, a clinic physician may make the determination as to whether to send a fasting specimen to the laboratory (eg, for a very high finger stick value that is probably diagnostic for DM) or to proceed to 2 hour GTT (eg, a finger stick value that is in the vicinity of 120 mg/dL)
- If fasting glucose is <120 mg/dL, proceed as follows:
- Instruct patient to drink 300 mL (10 oz. cup) of water. For males and non-pregnant females, administer 75 g of GlucolaTM. Patient must complete ingestion of GlucolaTM within 5 to 10 minutes.
- Record the time of the start of GlucolaTM (all timings proceed from this point).
- Draw blood at 2 hours after ingestion of 75 g GlucolaTM.
- Label tubes with the patient’s full name, fasting or 2 hour, and date and time of collection.
- If symptoms such as pallor, sweating, fainting, or marked nausea develop during test, procedure should be discontinued and repeated at another time.
- For further information see Patient Preparation for Glucose Tolerance Testing in Specimen Collection and Preparation.
Specimen Stability
| Temperature | Time |
| Refrigerated | 72 hours |
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Gross hemolysis
For NCMC only: Gross lipemia if plasma - Serum specimen needed if Grossly Lipemic.
For NCMC only: Gross lipemia if plasma - Serum specimen needed if Grossly Lipemic.
Methodology
Hexokinase Bichromatic Endpoint
Setup Schedule
Monday through Sunday; Continuously
Report Available
Same day
Reference Range
<135 mg/dL
Critical Values:
0-31 days <40 mg/dL or >300 mg/dL
31 days - 150 years: <50 mg/dL or >500 mg/dL
Critical Values:
0-31 days <40 mg/dL or >300 mg/dL
31 days - 150 years: <50 mg/dL or >500 mg/dL
Clinical Significance
The Glucose Tolerance Test is designed to evaluate patients suspected of having diabetes mellitus. This study is two hours in duration, includes a 75g dose of glucose, and requires two separate blood collections: Fasting (Baseline) and 2 hours post glucose load.
Performing Laboratory
Banner Fort Collins Medical Center Laboratory
Mckee Medical Center Laboratory
North Colorado Medical Center Laboratory
Summit View Laboratory
