75 gram, fasting, 2-hour, non-gestational glucose tolerance
Test Mnemonic
GTNG2
CPT Codes
- 82951 - QTY (1)
Includes
- Fasting
- 1 Hour
- 2 Hour
Performing Laboratory
Cleveland Clinic Laboratories
Specimen Requirements
| Volume | Type | Container | Collect Temperature | Transport Temperature | Special Instructions |
|---|---|---|---|---|---|
| 1 mL | Plasma | Potassium oxalate/sodium fluoride (Gray) | Centrifuge and refrigerate. | Aliquot into CCL aliquot tube |
Minimum Specimen Requirements
| Volume | Type | Container | Collect Temperature | Transport Temperature | Special Instructions |
|---|---|---|---|---|---|
| 0.3 mL |
Stability
| Environmental Condition | Description |
|---|---|
| Ambient | 24 hours |
| Refrigerated | After removed from cells: 72 hours |
| Frozen | Unacceptable |
Days Performed
Sun - Sat
Turnaround Time
8 hours
Methodology
| Name | Description |
|---|---|
| Glucose Hexokinase |
Reference Range
| 1 Hour | |||||
|---|---|---|---|---|---|
| Sex | Age From | Age To | Type | Range | Range Unit |
| Normal | See comment | Urgent | >500 | mg/dL | Urgent | Inpatient only: 40-49 mg/dL (First result only, once every 24 hours.) | mg/dL | Critical | <40 | mg/dL |
| 2 Hour | |||||
| Sex | Age From | Age To | Type | Range | Range Unit |
| Normal | 74-139 | mg/dL | Urgent | >500 | mg/dL | Urgent | Inpatient only: 40-49 mg/dL (First result only, once every 24 hours.) | mg/dL | Critical | <40 | mg/dL |
| Fasting | |||||
| Sex | Age From | Age To | Type | Range | Range Unit |
| Normal | 74 - 99 | mg/dL | Urgent | >500 | mg/dL | Urgent | Inpatient only: 40-49 mg/dL (First result only, once every 24 hours.) | mg/dL | Critical | <40 | mg/dL |
Special Info
Patient should be fasting at least 8 hours prior to the test. Collect a fasting specimen. Then administer 75 grams of Dextrose within 5 minutes. Collect specimens at 1 and 2 hours post glucose load. Indicate collection time on each specimen.
Clinical Info
Confirmation of diabetes mellitus American Diabetes Association guidelines state a diabetes mellitus diagnosis is preliminarily made when the fasting plasma glucose meets or exceeds 126 mg/dL and/or the 2 hr glucose tolerance meets or exceeds 200 mg/dL. In the absence of unequivocal hyperglycemia, results should be confirmed with repeat testing. Patients are at increased risk for diabetes mellitus (prediabetes) when the fasting glucose is 100 to 125 mg/dL or the 2 hr glucose tolerance result is 140 to 199 mg/dL. A diagnostic cutoff for the 1 hr time point is not established, and should be clinically determined.