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Glucose Tolerance Test, 2 Hour
MessageChemistry
Test Code
LAB1237005
Alias/See Also
Glucose Tolerance Test Fasting
2 HR GTT
2 HR GTT
CPT Codes
82950
Preferred Specimen
Light green top tube (lithium heparin plasma)
Minimum Volume
Whole blood: 600 uL (one full light-green-top microtainer or two full red-top microtainers).
Serum/plasma: 300 uL plasma.
Serum/plasma: 300 uL plasma.
Other Acceptable Specimens
Gold top (serum separator tube) or Red Top
Instructions
Not recommended to diagnose gestational diabetes.
If patient has order for 2 hour GTT and diagnosis of pregnancy, ask how many weeks pregnant. If <15 weeks, okay to proceed with standard 2 hour GTT.
If >15 weeks call office to confirm order and ask if they would like to switch to 1 or 3 hour GTT as 2 hour Gtt is not built in Epic to properly diagnose gestational diabetes. If provider insists on 2 hour GTT, process and add comment to order. Draw the fasting glucose. If the results are less than 126mg/dl, give the patient 75 grams of glucola.
Draw the next specimen 2 hours later. (2 specimens total)
Note: If there is a request for a 2 hr GTT on a patient <16 years of age, weigh the patient. Document in patient chart patient weight and adjusted oral glucose dose given. If patient weighs >95 lbs (43 kg), adjust oral glucose dose to 1.75 gm/kg as seen below. If ≥16 years and/or >95 lbs (43 Kg), standard dosing applies.
If patient has order for 2 hour GTT and diagnosis of pregnancy, ask how many weeks pregnant. If <15 weeks, okay to proceed with standard 2 hour GTT.
If >15 weeks call office to confirm order and ask if they would like to switch to 1 or 3 hour GTT as 2 hour Gtt is not built in Epic to properly diagnose gestational diabetes. If provider insists on 2 hour GTT, process and add comment to order. Draw the fasting glucose. If the results are less than 126mg/dl, give the patient 75 grams of glucola.
Draw the next specimen 2 hours later. (2 specimens total)
Note: If there is a request for a 2 hr GTT on a patient <16 years of age, weigh the patient. Document in patient chart patient weight and adjusted oral glucose dose given. If patient weighs >95 lbs (43 kg), adjust oral glucose dose to 1.75 gm/kg as seen below. If ≥16 years and/or >95 lbs (43 Kg), standard dosing applies.
Specimen Stability
Ambient: up to 24 hours. Refrigerated: 7 days. Frozen: 1 year.
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Hemolyzed, contaminated, QNS, not enough volume
FDA Status
Approved
Setup Schedule
Everyday
Report Available
Same day
Limitations
In fresh specimens, catalase released from the lysis of red blood cells causes a negative bias in glucose results. The degree of bias is proportional to the degree of hemolysis. In fresh samples, a negative bias of up to 10% may be observed with a level of hemolysis associated with a hemoglobin concentration of 250 mg/dL.
Reference Range
<180 mg/dL
Performing Laboratory
Hoag Newport/ Hoag Irvine
