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Test Code LACTOL Lactose Tolerance, LAB2571

Performing Laboratory

St. Luke's Hospital Cedar Rapids

Specimen Requirements


Preferred: Green-top (lithium heparin) tube

Acceptable: Gold-top serum gel tube or plain red-top tube
Specimen Volume: 0.1 mL of plasma or serum

Collection Instructions: Patient must be fasting (however, water may be taken)

                 and refrain from smoking during test. A fasting specimen will be drawn, then

                 a 50 g lactose dose given. Additional specimens will be drawn at 15 minutes, 

                 30 minutes, 60 minutes, 90 minutes, and 120 minutes post dose.

Note: Label specimen appropriately (plasma and fasting, 15 minutes, 30 minutes, 60 minutes, 90 minutes, or 120 minutes post dose).



Reference Values

A peak maximal rise of 25 mg/dL in the blood glucose signifies normal lactase activity. A peak rise below 20 mg/dL strongly suggests lactase deficiency.

False-positive reactions may occur in the presence of vomiting, gastric stasis, or severe diarrhea. False-negative reactions may occur in the presence of diabetes.

Day(s) Test Set Up

Monday through Friday

Useful For

Samples should be separated immediately or within 2 hours.  Separated specimens should be analyzed immediately or kept at 2 – 8°C and analyzed within 7 days. For longer storage, samples may be frozen at -20°C for up to 3 months.



Test Classification and CPT Coding

82951-3 Specimens

82952-Each additional specimen

Analytic Time

Within 3 hours upon beginning testing