Specimen Requirement

1. Lithium heparin plasma (green) is the specimen of choice. 0.5mL
2. Serum (red/gold) and EDTA plasma (purple) are also acceptable sample types.
3. It is recommended that the serum or plasma be separated from contact with cells within 30 minutes from time of collection.
4. Serum/plasma glucose specimens are stable for 8 hours at 25°C, or 72 hours at 4°C. 

A fasting specimen is assayed prior to the patient consuming the glucose drink. If the fasting result is acceptable the patient is given the appropriate quantity of glucose drink.

Serum or lithium heparin plasma collected at specified time intervals after the patient has consumed 100 gm of glucose drink. 

• Fasting specimen must be tested and less than 126 mg/dl before the glucose drink is given.
• If the fasting glucose is ≥ 126 mg/dL contact the ordering physician before continuing the tolerance test.
• If the physician is not available contact a pathologist before proceeding.
• The patient should have had at least 3 days of unrestricted diet and normal physical activity.
• Instruct the patient to remain seated or reclined throughout the procedure.
• The patient may have water to drink but nothing else. Coffee and smoking materials are prohibited.
• Children under 16 years will be given a glucose load based upon their actual body weight. Include information regarding child’s weight when requesting the test.
• The test is administered in the morning following a fast of between 8-10 hours.
• The NIH (National Institute of Health) recommends a 2 hour procedure with blood collected at fasting and 2 hours; (3 hour procedure in pregnant subjects, with an additional specimen collected at the first and third hour. See Glucose Tolerance
  Gestational.)
• A physician can request a longer OGTT (Oral Glucose Tolerance Test) with different dosages and specimen collection intervals. Consult a pathologist when this is ordered.