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Tests and diagnosis
By Mayo Clinic staffYour doctor may suspect lactose intolerance based on your symptoms and your response to reducing the amount of dairy foods in your diet. Your doctor can confirm the diagnosis by conducting one or more of the following tests:
- Lactose tolerance test. The lactose tolerance test gauges your body's reaction to a liquid that contains high levels of lactose. Two hours after drinking the liquid, you'll undergo blood tests to measure the amount of glucose in your bloodstream. If your glucose level doesn't rise, it means your body isn't properly digesting and absorbing the lactose-filled drink.
- Hydrogen breath test. This test also requires you to drink a liquid that contains high levels of lactose. Then your doctor measures the amount of hydrogen in your breath at regular intervals. Normally, very little hydrogen is detectable. However, if your body doesn't digest the lactose, it reaches your colon and ferments, causing hydrogen and other gases to be released, absorbed by your intestines and eventually exhaled. Large amounts of exhaled hydrogen measured during a breath test indicate that you aren't fully digesting and absorbing lactose.
- Stool acidity test. For infants and children who can't undergo other tests, a stool acidity test may be used. Undigested lactose ferments in the colon, creating lactic acid and other acids that can be detected in a stool sample. The lactose tolerance test and the hydrogen breath test may be dangerous for infants and children who can't tolerate high levels of lactose required for those tests.
References
- Lactose intolerance. In: Ferri FF. Ferri's Clinical Advisor 2010. Philadelphia, Pa.: Mosby; 2010. http://www.mdconsult.com/das/book/body/178347893-5/0/2088/0.html. Accessed Jan. 14, 2010.
- Marchiondo K. Lactose intolerance: A nursing perspective. Medsurg Nursing. 2009;18:9.
- Lomer MCE, et al. Review article: Lactose intolerance in clinical practice - Myths and realities. Alimentary Pharmacology & Therapeutics. 2008;27:93.
- Lactose intolerance. National Institute for Diabetes and Digestive and Kidney Diseases. http://digestive.niddk.nih.gov/ddiseases/pubs/lactoseintolerance/index.htm. Accessed Jan. 14, 2010.
- Lactose intolerance. American Gastroenterological Association. http://www.gastro.org/wmspage.cfm?parm1=854. Accessed Jan. 14, 2010.
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