The standard 2 hour glucose tolerance test is useful for screening for type 2 diabetes in non-pregnant patients.

Allina Health provides an FDA-approved prescription glucose drink that is free from dyes and is certified kosher. An order for an Alternative Glucose Tolerance, 2 hr (LAB15142) must be placed by the provider, if the decision is made to use an alternate source.

• See patient preparation information on Specimen tab for more details

Fasting is required prior to sample collection

Fasting for a blood test

• The decision to use alternate glucose source for OGTT testing, is the responsibility of the treating provider and patient and must be ordered by the provider.
• The provider must place the appropriate Alternative Glucose Tolerance, 2 hr (LAB15142) and provide any instructions to the patient. Testing will be delayed if a standard OGTT order was placed and the patient comes to the lab with an alternate glucose source. 
• The patient must bring the alternate glucose source for the test. The laboratory does not provide alternate glucose sources or give patient instructions for using alternate sources.  
• If a patient shows up with an outside glucose drink or candy but the provider placed a standard GTT order, testing cannot proceed until the provider places the correct order.

Lt green plasma separator (PST)

1. Draw a fasting specimen
   • Immediately following collection, mix sample thoroughly by gentle inverting 8 - 10 times to prevent clotting
   • If the fasting glucose is >126, cancel the testing as not indicated and notify the ordering physician
2. Give fasting patient 75 gm glucose solution
   • Must be consumed within 10 minutes
3. Draw second specimen at 2 hours
4. Label with time and hour collected

Spin within two (2) hours of sample collection

Lt green plasma separator (PST)

Gold serum separator (SST) tube

Grey Sodium flouride (NaFl)

Lavender (EDTA), 4mL

Gold:

1. Allow sample to clot for a minimum of 30 minutes
2. Spin within two (2) hours of sample collection

Dk green/lavender: 

1. Spin
2. Transfer the plasma to an AHL False Bottom Plasma/Serum Transport Tube labeled as the appropriate plasma type, within two (2) hours of sample collection

Grey:

If a grey top tube will not reach the Central Laboratory within 24 hours of collection, it should be spun down, and the plasma transferred to an AHL False Bottom Plasma/Serum Transport Tube labeled as NaFl plasma. 

Additional testing cannot be added on to this sample.

Gold serum separator (SST) tube

Grey Sodium flouride (NaFl) or

False bottom plasma/serum transport vial/tube (AHL)

Serum/plasma:

Refrigerated - 3 days

Ambient - 8 hours

• Improper labels (unlabeled or mislabeled)
• Hemolysis (some procedures)
• Improper anticoagulant or ratio
• Delay in transport
• Improper storage temperature affecting results
• Inappropriate timing of collection
• Improper container
• Leaking container resulting in compromised specimen
• Quantity not sufficient (QNS)

Hexokinase

The 2-hour glucose tolerance protocol for gestational diabetes is not orderable or supported at Allina Health. This is to ensure that all pregnant patients receive the same standard of diagnostic care. The gestational GTT tests available from our laboratory are the Glucose, gestational screen and the Glucose tolerance, 3 hour gestational, recommended by the American College of Obstetrics and Gynecology (ACOG). If a 2-hour gestational GTT is requested, the provider must be contacted to either (1) place a new order for the Glucose gestational screen (1-hour); or, (2) direct the patient to a different laboratory for administration of the 2-hour protocol.

Medical necessity