ARUP's Laboratory Test Directory
| 0020407: Lactose Tolerance |
| Test Mnemonic: LACTOL | |
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Methodology: Enzymatic
Performed: Sun-Sat Reported: Within 24 hours |
| Specimen Required: | |
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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 |
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| Reference Interval: |
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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: | |
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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.
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| CPT Code(s): | |
| 82951 Tolerance test (GTT); 82952 x2 Tolerance test, each additional beyond three specimens |