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Glucose, Fasting and Postprandial/2-Hour

Test Code


CPT Code(s)

82947 (x2)

Patient Preparation

Fasting required. Fasting is defined as no consumption of food or beverage other than water for at least 8 hours before testing.

Preferred Specimen(s)

Two - 1 mL plasma specimens collected in fluoride/oxalate (gray-top) tubes

Minimum Volume

0.5 mL each specimen

Alternative Specimen(s)

Plasma from fluoride/oxalate (gray-top) tube in a plastic screw-cap vial • Serum (separated from cells immediately) in a plastic screw-cap vial • Spun SST® • Plasma from lithium heparin (green-top) tube in a plastic screw-cap vial • Plasma from sodium heparin (green-top) tube in a plastic screw-cap vial

Collection Instructions

First specimen obtained fasting. Second specimen obtained 2 hours following a meal. Label each specimen with the specific draw time. Serum and plasma submissions must be separated from cells.

Transport Container

Fluoride/oxalate (gray-top) tubes

Transport Temperature

Room temperature

Specimen Stability

Room temperature: 4 days
Refrigerated: 7 days
Frozen: 28 days

Whole blood (gray-top) tube
Room temperature: 24 hours
Refrigerated: 72 hours
Frozen: Unacceptable

Sodium fluoride plasma
Room temperature: 7 days
Refrigerated: 7 days
Frozen: 28 days

Heparinized plasma
Room temperature: 48 hours
Refrigerated: 7 days
Frozen: 28 days

Note: Serum and plasma submissions must be separated from cells

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


Spectrophotometry (SP)

Performing Laboratory

Quest Diagnostics - Southwest Region


Glucose levels may be depressed if sample is left on clot for an excessive length of time.

Reference Range(s)

Glucose, Plasma 65-99 mg/dL
Glucose, Postprandial/2-Hour  <140 mg/dL

Clinical Significance

Postprandial glucose levels may be abnormally high in patients with gestational diabetes. If results are positive, and the patient is pregnant, a 3-hour oral glucose tolerance test should be performed for confirmation of gestational diabetes.

LOINC®' Code(s)

The Result and LOINC information listed below should not be used for electronic interface maintenance with Quest Diagnostics. Please contact the Quest Diagnostics Connectivity Help Desk for more information at 800-697-9302.

NOTE: The codes listed in the table below are not orderable Test Codes.

Result NameLOINC CodeComponent Name
25014500GLUCOSE, PLASMA1558-6Glucose^post CFst
25014600GLUCOSE, POSTPRANDIAL/ 2 HOUR1521-4Glucose^2H post meal

Reference ranges are provided as general guidance only. To interpret test results use the reference range in the laboratory report.

The CPT codes provided are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payer being billed.

LOINC assignment is based on a combination of test attributes, including the method used by the performing laboratory. For tests not performed by Quest Diagnostics, codes are assigned by the performing laboratory.

* The tests listed by specialist are a select group of tests offered. For a complete list of Quest Diagnostics tests, please refer to our Directory of Services.