ARUP's Laboratory Test Directory

0020407: Lactose Tolerance

Test Mnemonic: LACTOL
Methodology: Enzymatic

Performed: Sun-Sat

Reported: Within 24 hours

Specimen Required:  
Collect: One 5 mL gray (sodium fluoride/potassium oxalate) for each timed determination. Recommend drawing specimens for baseline (fasting), 30 minutes, 60 minutes, 120 minutes, and 180 minutes after lactose load. (Min: 3 mL gray for each timed determination)

Transport: 1 mL plasma for each timed determination at 2-8°C. (Min: 0.5 mL)  Submit specimen in an ARUP Standard Transport Tube.

Pediatric Collection/Transport: 1 mL in a 3 mL gray-top for each time point at 2-8°C. Recommend drawing samples for baseline (fasting), 30 minutes, 60 minutes, 120 minutes, and 180 minutes after lactose load.

Remarks: Separate plasma from cells ASAP.  Fasting patient should be given 50 g lactose in 200-300 mL water consumed in five to 10 minutes. Note: if severe lactose deficiency is suspected, the dose should be lowered.

Stability: After separation from cells: Ambient: 24 hours; Refrigerated: 3 days; 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 lactose deficiency.



CPT Code(s):
82951 Tolerance test (GTT); 82952 x2 Tolerance test, each additional beyond three specimens

 

 

 
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