Test Details
Methodology
Enzymatic
Result Turnaround Time
Within 1 day
Turnaround time is defined as the usual number of days from the date of pickup of a specimen for testing to when the result is released to the ordering provider. In some cases, additional time should be allowed for additional confirmatory or additional reflex tests. Testing schedules may vary.
Test Includes
Glucose level two hours after meal or glucose drink
Use
Only a minority of patients with diabetes mellitus have the classic symptoms of polyuria, polyphagia, polydipsia, and weight loss. The two-hour postprandial glucose is extensively used to establish the diagnosis of diabetes mellitus. It may be used along with FBS to follow patients with impaired glucose tolerance.
Follow up women who had gestational diabetes, of whom most revert after delivery to normal glucose tolerance (up to half ultimately become diabetic).
It is used as part of the work-up for hypertriglyceridemia, neuropathy, retinopathy, glycosuria and for certain types of renal diseases. Work-up of vulvovaginitis, blurred vision, fatigue, and some instances of urinary tract infections.
Causes of postprandial hypoglycemia include alimentary type (commonly secondary to prior gastrointestinal surgery); reactive hypoglycemia without prior gastrointestinal surgery—alimentary or spontaneous, functional, idiopathic, indeterminate; some prediabetics; leucine-induced; fructose-induced; galactosemia; indeterminate group.
Contraindications
References
Specimen Requirements
Specimen
Serum or plasma
Volume
1 mL
Minimum Volume
0.5 mL serum or 0.5 mL plasma (Note: This volume does not allow for repeat testing.)
Container
Gel-barrier tube (1) or gray-top (sodium fluoride/potassium oxalate plasma) tube (1)
Collection Instructions
Collect specimen two hours from the beginning of meal. Separate serum or plasma from cells within 45 minutes of venipuncture. Gray-top tubes only, may be submitted without centrifugation. Label tube with patient's name and collection time.
Stability Requirements
Temperature | Period |
|---|---|
Room temperature | 14 days |
Refrigerated | 14 days |
Frozen | 14 days |
Freeze/thaw cycles | Stable x3 |
Reference Range
65−139 mg/dL
Storage Instructions
Maintain specimen at room temperature.
Patient Preparation
Adequate meal or 75-gram glucose load two hours before two-hour postprandial glucose, as specified by the patient's physician. Patient is allowed usual meal (breakfast or lunch). Patient must complete meal within 15 to 20 minutes.
Causes for Rejection
Stressed patients (surgery, infection, corticosteroids) should not have GTT; specimens not labeled with collection time
LOINC® Map
| Order Code | Order Code Name | Order Loinc | Result Code | Result Code Name | UofM | Result LOINC |
|---|---|---|---|---|---|---|
| 002022 | Glucose, Two-Hour Postprandial | 1521-4 | 002022 | Glucose, Two-Hour Postprandial | mg/dL | 1521-4 |
| Order Code | 002022 | |||||
| Order Code Name | Glucose, Two-Hour Postprandial | |||||
| Order Loinc | 1521-4 | |||||
| Result Code | 002022 | |||||
| Result Code Name | Glucose, Two-Hour Postprandial | |||||
| UofM | mg/dL | |||||
| Result LOINC | 1521-4 |