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HelpTest Code LAB169 Glucose Tolerance 2 Hour
Useful For
Aiding in the diagnosis of diabetes mellitus
Methodology
Enzymatic reference method with hexokinase
Performing Laboratory
Bozeman Health Laboratory Services
Specimen Requirements
Patient Preparation:
- Patient should maintain a normal carbohydrate diet (at least 300 g of carbohydrates per day) for 3 days prior to test.
- Patient should follow physicians instructions regarding fast.
- Patient must not eat or drink during testing. Ice chips may be given to moisten mouth.
Performance of Test:
- Draw a fasting blood specimen.
- Have adult patient drink entire 75 g of glucose tolerance beverage.
- Ingestion should be completed within 10 minutes. Timing starts at this point.
- If patient vomits, cancel test and reschedule.
- Exactly 1-hours after ingestion of glucose beverage, draw blood.
- Exactly 2-hours after ingestion of glucose beverage, draw blood.
Specimen Collection:
Specimen Type: Plasma or serum
Container/Tube: Light-green top (lithium heparin gel), red top or gold top
Specimen Volume: 1 mL
Specimen Minimum Volume: 0.5 mL
Collection Instructions: Label specimen with time of draw. Complete clot formation should take place before centrifugation. Spin down and separate cells within half an hour of collection.
Additional Information
-
Includes fasting and 2-hour plasma tests for glucose
Specimen Transport Temperature
Ambient <8 hours/Refrigerated >8 hours
Specimen Stability
| Specimen Type | Temperature | Time |
|---|---|---|
| Plasma or serum | Ambient | 8 hours |
| Refrigerated | 3 days |
Note: Glycolysis decreases serum glucose by approximately 5% to 7% per hour in normal, uncentrifuged, coagulated blood at ambient temperature.
Reference Values
Fasting Glucose: 70-99 mg/dL
2-hour Glucose: 70-139 mg/dL
Critical values (automatic call-back): ≤50 mg/dL or ≥400 mg/dL
Day(s) Test Set Up
Monday through Sunday
Test Classification and CPT Coding
82947