ARUP's Laboratory Test Directory

Lactose Tolerance : 0020407

Mnemonic: LACTOL

Methodology: Quantitative Enzymatic
Performed: Sun-Sat
Reported: Within 24 hours
Specimen Required: Patient Prep: Recommend drawing specimens for baseline (fasting), 30 minutes, 60 minutes, 120 minutes, and 180 minutes after lactose load (lactose may be obtained from a hospital pharmacy). Fasting patient should be given 50 g lactose in 200-300 mL water consumed in 5 to 10 minutes. Note: If severe lactase deficiency is suspected, the dose should be lowered.

Collect: Gray (sodium fluoride/potassium oxalate). Collect separate tube for each timed point.

Specimen Preparation: Separate plasma from cells ASAP or within 2 hours of collection. Transfer 1 mL plasma for each time point to individual ARUP Standard Transport Tubes. (Min: 0.5 mL per timed determination)

Storage/Transport Temperature: Refrigerated.

Stability (collection to initiation of testing): After separation from cells: Ambient: 24 hours; Refrigerated: 72 hours; Frozen: 1 year
Reference Interval:
Fasting glucose: 64-128 mg/dL
Normal lactose tolerance: 20-30 mg/dL elevation in glucose over fasting level after 50 g lactose load.
Interpretive Data: A less than 20 mg/dL increase in glucose over the fasting level, with gastrointestinal symptoms after a lactose load is considered abnormal and consistent with lactase deficiency.
Note: Glucose in whole blood at room temperature undergoes glycolysis at a rate of approximately 7 percent each hour.
CPT Code(s): 82951; add 82952 x2 each specimen beyond three