ARUP's Laboratory Test Directory

Glucose Tolerance Test : 0020542

Mnemonic: GTT

Ordering Recommendation: Use to diagnose gestational diabetes mellitus, diabetes mellitus, or impaired glucose tolerance.
Methodology: Quantitative Enzymatic
Performed: Sun-Sat
Reported: Within 24 hours
Specimen Required: Patient Prep: Patient should fast for at least eight hours prior to collection of fasting specimen.

Collect: Collect 2 timed specimens (fasting and 120 minutes). Gray (sodium fluoride/potassium oxalate). Collect separate tube for each timed specimen.

Specimen Preparation: Separate plasma from cells and refrigerate within 2 hours of collection. Transfer 1 mL plasma per time point to individual ARUP Standard Transport Tube. (Min: 0.2 mL/time point)

Storage/Transport Temperature: Refrigerated.

Stability (collection to initiation of testing): After separation from cells: Ambient: 24 hours; Refrigerated: 1 week; Frozen: 1 year
Reference Interval:
Glucose (fasting and 120 min). Interpretation available on consultation with medical director.
Note: Administer 75 g glucola. Do not mix with water unless directions on product label indicate to do so. The patient should be fasting for at least eight hours prior to start of test, should remain inactive, and receive nothing by mouth (including tobacco) during test period.  A small sip of water or ice is permissible. Reasons for invalid results include emesis and conditions which delay stomach emptying.
CPT Code(s): 82947; 82950
Cross References: Glucose (Glucose Tolerance Test)