Sign in →

Test Code 2500081 GTT 3 HR

Specimen Requirements

2.0 mL Serum

Special Instructions

Test Requirements:

Fasting whole blood glucose level <130 mg/dl or serum/plasma fasting glucose <140 mg/dl.   If glucose levels are higher than the fasting limits allow the patient’s physician must be contacted.   Only if the physician dictates it is okay to proceed may testing continue.  Otherwise, testing must be discontinued and the test cancelled.

Dosage:

Adults – 1 bottle (100 grams) glucose beverage

Children – 1.75gm/kg of body weight (1 kg=2.2 lbs), then same as 1 hr.

Specimens:

A whole blood finger-stick glucose may be performed for the fasting specimen.  If the finger stick glucose is >130 mg/dl, a serum /plasma specimen must be drawn and tested.  All other specimens will be serum/plasma.  Acceptable serum/plasma specimens are oxalated (gray-top) plasma, lithium heparin (green-top) plasma, plain red-top serum tubes or SST (Black Red-Top) serum tube.

Procedure:

A fasting blood specimen and urine should be collected and tested.  If values are acceptable to continue, dose patient, collect a blood and urine specimen as follows, after patient finish glucose beverage:

30 minutes, 1 hour, 2 hours, and 3 hours.

Dosage:

Adults – 1 bottle (100 grams) glucose beverage

Children – 1.75gm/kg of body weight (1 kg=2.2 lbs), then same as 1 hr.

 

Example:

 

If patient finishes the glucose beverage at 0915 the drawing schedule will be as follows.

  • 30 minute draw – 0945
  • 1 hour draw – 1015
  • 2 hour draw – 1115
  • 3 hour draw - 1215

 

Notes:

  • Do not allow patient to leave treatment area.
  • If patient becomes ill and vomits test must be stopped and physician notified.
  • If patient eats or drinks (other than small amount of water) test must be stopped and physician notified.
  • Blood specimens may still be collected and tested, even if patient cannot collect a urine specimen.  A comment will be added to the tolerance results that states that patient was, “unable to void”.

Reference Values

 

 

    Adults   OB Patients
Fasting   65-95 mg/dL   105 mg/dL
30 minutes   30-60 mg/dl above fasting   no specimen
1 hour   20-50 mg/dl above fasting   190 mg/dL
2 hours   5-15 mg/dl above fasting   165 mg/dL
3 hours   Fasting level or below   145 mg/dL
        (considered gestational diabetes if two or more values are elevated)

 

Specimen Stability Information

3 days 2-8°C

Day(s) Test Set Up

Monday through Sunday

CPT

82951

LOINC

50586-7

Methodology

Hexokinase