Glucose Tolerance Test, 4 Specimens
Quest Diagnostics
Sample type: Plasma
Requires fasting: Yes
Phlebotomy required
Details
Glucose Tolerance Test, 4 Specimens - For appropriate interpretation of this test, the patient must fast overnight and ingest a 75 g load of glucose, immediately after a fasting specimen is obtained. (for children, the glucose load is 1.75 g/kg of body weight, up to 75). The diagnosis of diabetes is made if glucose exceeds 200 mg/dL in the 2 hour specimen and in any preceding specimen.
- Glucose, Fasting
- Glucose, 2nd specimen
- Glucose, 3rd specimen
- Glucose, 4th specimen
Estimated days for results: Results should be available in 2 - 5 business days after the sample is collected
2–5 business days
Diagnostic Criteria for Diabetes Mellitus
Glucose Value (mg/dL)
Interpretation Fasting 1 Hr Tolerance 2 Hr Tolerance
Normal <100 Not established <140
Impaired Fasting 100–125
Impaired Tolerance 140–199
Diabetes ≥126* ≥200 ≥200*
*Must be confirmed by testing on a subsequent day.
Specimen 1: 65–99 mg/dL
- Fasting before a blood draw means you don't eat or drink anything except water.
- Your doctor should provide any special instructions related to fasting for your test. Always follow your doctor's instructions.
Blood Draw Options with Fullscript
Fullscript offers several convenient phlebotomy options to complete your lab testing:
Quest Diagnostics Patient Service Centers (PSC)
- Location: Visit a nearby Quest Diagnostics Patient Service Center.
- Cost: $10 sample collection fee (paid during lab order checkout).
- Scheduling: Schedule your appointment here. Appointments are recommended to reduce wait times. Walk-ins are accepted, but may experience delays. Aim to arrive 10 minutes before your appointment.
- Collection Instructions:
- Bring a valid ID.
- Bring your digital or printed requisition form, available in the Labs tab of your Fullscript account.
- Check-in: Scan the QR code from your confirmation email or follow kiosk instructions.
- More Info: Quest Diagnostics blood draw guide
Getlabs Mobile Phlebotomy
- Location: Sample collection at your home or office.
- Cost: $85 sample collection fee (paid during lab order checkout).
- Availability: Available in most locations – enter your ZIP code during checkout to confirm.
- Scheduling: Schedule your appointment here through your Fullscript account.
- Collection Instructions:
- Have your digital or printed requisition form and valid ID ready.
- Your phlebotomist will contact you by phone to coordinate arrival.
- More Info: Getlabs blood draw guide
- Preferred Specimen(s): Four - 1 mL plasma specimens collected in fluoride/oxalate (gray-top) tubes
- Alternative: NA
- Minimum Volume: 0.5 mL
- Collection Instructions: NA
- Transport Container: Fluoride/oxalate (gray-top) tube
- Transport Temperature: Room Temperature
- Specimen Stability:
- Room temperature: 7 days
- Refrigerated: 7 days
- Frozen: 28 days
- Reject Criteria:
- Unspun serum or plasma separator tube (SST or PST) • Red-top or green-top tube (serum or heparinized plasma not separated from cells) • Anticoagulants other than lithium heparin, sodium heparin or fluoride/oxalate
State restrictions:
Patient can't order this test if they are located in Hawaii, Puerto Rico, New Jersey, New York, or Rhode Island
