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Glucose, 2-Hour Post Prandial

PC Glucose

Test Codes

Prescribed Meal: EPIC: LAB5061, Beaker: GL2PC, Glucola Load: EPIC: LAB5065, Beaker: GLUPG

Department

Chemistry

Instructions

• Record the exact time drawn on the tubes.
• Specimen collection should occur 2 hours after the patient consumes a physician prescribed meal.
• NOTE: If the physician does not prescribe a specific menu, the Laboratory will administer a 75 g Glucola load. Order the test as follows:
  
  

  • Prescribed Meal: EPIC: LAB5061, Beaker: GL2PC

  • Glucola Load: EPIC: LAB5065, Beaker: GLUPG

Specimen Collection Criteria

Collect (preferred specimen): One Gray-top Potassium Oxalate/Sodium Fluoride tube drawn exactly two hours after the completion of the prescribed meal or administration of the oral glucose load. (Minimum Whole Blood: 4.0 mL)
Also acceptable: One Gold-top SST tube (Minimum Whole Blood: 4.0 mL) drawn under the same guidelines as given above.

Contact Laboratory for acceptability of other tube types.
See Minimum Pediatric Specimen Requirements for Microtainer^® collection.

Physician Office/Draw Specimen Preparation

Let SST specimens clot 30-60 minutes then immediately centrifuge to separate serum from cells. Refrigerate (2-8°C or 36-46°F) the centrifuged SST tube within two hours of collection.

Maintain Gray-top tubes refrigerated (2-8°C or 36-46°F) prior to courier transport.

NOTE: If serum or heparinized plasma is left in contact with blood cells for extended periods, glucose will be metabolized. Glucose levels decrease by about 5-7% or 7 mg/dL/hour at room temperature in normal specimens containing normal numbers of RBC's and WBC's. 

Preparation for Courier Transport

Transport: Centrifuged SST or Gray-top tube, refrigerated (2-8°C or 36-46°F). (Minimum: 0.5 mL)

Rejection Criteria

• Grossly hemolyzed specimens.
• Inadequately centrifuged Microtainers^® or Gold-top tubes.
• Red-top tubes with serum not separated from cells within two hours of collection.
• Gray-top tubes that are not received within 24 hours of the time of collection. 

In-Lab Processing

Let SST specimens clot 30-60 minutes. Centrifuge SST, Gray-top tubes, or Microtainers^® to separate serum or plasma from cells. Deliver immediately to the appropriate testing station.

Storage

Specimen Stability for Testing:

Centrifuged SST Tubes and Microtainers^® with Separator Gel
Room Temperature (20-26°C or 68-78.8°F): 2-4 hours
Refrigerated (2-8°C or 36-46°F): 7 days
Frozen (-20°C/-4°F or below): Unacceptable

Red-top Tubes and Microtainers^® without Separator Gel
Room Temperature (20-26°C or 68-78.8°F): 2-4 hours
Refrigerated (2-8°C or 36-46°F): Unacceptable
Frozen (-20°C/-4°F or below): Unacceptable

Gray-top Tubes
Room Temperature (20-26°C or 68-78.8°F): 24 hours
Refrigerated (2-8°C or 36-46°F): 7 days
Frozen (-20°C/-4°F or below): Unacceptable

Serum Specimens (Pour-Overs)
Room Temperature (20-26°C or 68-78.8°F): 2-4 hours
Refrigerated (2-8°C or 36-46°F): 7 days
Frozen (-20°C/-4°F or below): 7 days

Plasma Specimens (Aliquots)
Room Temperature (20-26°C or 68-78.8°F): 2-4 hours
Refrigerated (2-8°C or 36-46°F): 7 days
Frozen (-20°C/-4°F or below): 7 days

Specimen Storage in Department Prior to Disposal:

Refrigerated (2-8°C or 36-46°F): 7 days

Laboratory

Dearborn Chemistry Laboratory
Farmington Hills Chemistry Laboratory 
Grosse Pointe Chemistry Laboratory 
Royal Oak Automated Chemistry Laboratory 
Troy Chemistry Laboratory
Taylor Chemistry Laboratory
Trenton Chemistry Laboratory
Wayne Chemistry Laboratory 

Performed

Sunday – Saturday, 24 hours a day.
Results available within 4 hours.

Reference Range

Fasting: 60-99 mg/dL.
2-Hour Post Prandial: Less than 140 mg/dL.

Test Methodology

Enzymatic, Spectrophotometry.

Interpretation

In a normal individual plasma/serum glucose levels vary only slightly during a 24-hour period and are usually in the range of 45-130 mg/dL. Following a meal, the glucose increase is rarely greater than 10-15 mg/dL and a 2-hour pc value should be less than 140 mg/dL. However, following a 75 g glucose load (as in glucose tolerance test), the increase in plasma glucose in a healthy middle-aged subject may be 20-50 mg/dL higher than if the same amount of carbohydrate was given as a meal. In healthy individuals over 65 years, a random glucose may increase to 180 mg/dL. In IDDM plasma glucose may fluctuate by as much as 150 mg/dL following food intake.

Hyperglycemia is most commonly due to either type 1 or 2 diabetes mellitus, but may occur with other major endocrine diseases (e.g., Cushing's disease, acromegaly), drugs (e.g., steroids) and pancreatic disease.

Hypoglycemia is probably best diagnosed by Whipple's triad:

1. Signs/symptoms, often precipitated by fasting.
2. Plasma/serum glucose less than 45 mg/dL.
3. Symptoms relieved by administration of glucose.

In older diabetic subjects, signs and symptoms of hypoglycemia may occur at levels greater than 45 mg/dL. Causes of hypoglycemia include reactive, drug or ethanol-induced, factitious, insulinoma, adrenocortical insufficiency, hypopituitarism, and massive liver disease.

If serum or heparinized plasma is left in contact with blood cells for extended periods, glucose will be metabolized. Glucose levels decrease by about 5-7% or 7 mg/dL/hour at room temperature in normal specimens containing normal numbers of RBC's and WBC's.

Clinical Utility

Glucose measurements are used in the diagnosis and management of disorders of carbohydrate metabolism; these include diabetes mellitus, neonatal hypoglycemia, idiopathic hypoglycemia, and pancreatic islet cell tumors.

CPT Codes

82947

Contacts

Last Updated

10/22/2023