Lactose Tolerance Test
Also known as: Lactose Consumption Test
Use
Evaluate lactose intolerance, malabsorption syndromes. May be abnormal with Crohn's disease, small bowel resections, jejunitis, Giardia lamblia infestation, Whipple disease, and cystic fibrosis.
Special Instructions
Patients must fast for eight hours before the test, and are not allowed to smoke or chew gum during the test. They are encouraged to drink a moderate amount of water (one to two glasses) and must remain seated or in bed during the test. Proper labeling of specimens is critical for accurate results.
Limitations
This test may return false positives due to normal insulin responses to carbohydrate loads. A normal response is characterized by a glucose increase of over 30 mg/dL, while a lactase deficiency shows an increase of less than 20 mg/dL. Since 25% of normal individuals have flat glucose tolerance tests, additional tests such as a glucose tolerance test might be necessary to confirm results.
Methodology
Automated Analyzer (Clinical Chemistry)
Biomarkers
LOINC Codes
- 69555-1
- 12638-3
- 26777-3
- 26778-1
- 26779-9
- 26780-7
Result Turnaround Time
1 day
Related Documents
For more information, please review the documents below
Specimen
Plasma
Volume
Full tube for each sample
Minimum Volume
1 mL each tube
Container
Gray-top (sodium fluoride) tube
Collection Instructions
Draw fasting sample prior to lactose administration. For children up to 12 years, administer 2 g/kg body weight with a maximum of 50 g in 250 mL water. For adults, administer 50 g in 250 mL water. Collect specimens at 30, 60, 90, and 120 minutes following lactose administration. Label each tube with the patient's name and time of drawing.
Patient Preparation
Patient should fast for eight hours before testing. No smoking or gum chewing allowed during the test. Patient is encouraged to drink a moderate amount of water during the test, and should remain seated or in bed.
Storage Instructions
Maintain specimen at room temperature.
Causes for Rejection
Gross elevation of fasting blood glucose; improper labeling
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 14 days |
| Refrigerated | 14 days |
| Frozen | 14 days |