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Test Code N.3HRGLU GLUCOSE TOLERANCE, 3 HR

Important Note

This test should be done in the morning after an overnight fast of between 8 and 14 hours, and after at least 3 days of unrestricted diet (150 or more grams carbohydrate per day) and unlimited physical activity. The patient should remain seated and should not smoke throughout the test. Patients can have nothing by mouth except water during test period.

GLUCOSE DOSE: 100 grams.

Each transfer tube must be clearly marked with time of draw.

Methodology

Automated Chemistry Analyzer

Specimen Requirements

Serum or Plasma

Container: SST tube or Lithium heparin plasma (green top tube)

Specimen Collection: 1 mL each specimen (minimum 0.5 mL each specimen)

  1. Draw fasting specimen just prior to 100 gram glucose load. Draw 30 minutes, 1 hour, 2 hour and 3 hour post-dose specimens.
  2. Clearly label specimens. Each transfer tube must be labeled with time of draw.  
  3. Allow specimen to clot completely if a serum (SST) was used for the draw.
  4. Separate serum (SST) or plasma (Lithium Heparin) from cells within 24 hours and transport refrigerated. If a red top tube is collected, separate serum from cells within 2 hours and place in separate plastic tube and cap immediately.
  5. Properly label specimen with patient's name, DOB, requisition number and type of tube drawn i.e. GREEN.

Alternate Specimens: Gray top (Sodium Fluoride)

Specimen Transport/Stability

Refrigerated: 24 hours on gel, 7 days poured off

Specimen Rejection

1.  Clotted specimen

2.  Exceeding stability requirements

3. Unlabeled specimen

Maximum Laboratory Time

24 - 48 hours

Reference Ranges

Glucose            mg/dL
Fasting         < 140
30 min         < 200
60 min         < 200
90 min         < 200
120 min         < 200

Reference ranges based on the recommendations of the American Diabetes Association.

It is the position of the ADA that prolonged testing beyond two hours is seldom needed from the clinical point of view.

Day(s) Test Set Up

Daily

Test Classification and CPT Coding

82951

82952