Lactose intolerance is gastrointestinal upset after having foods that have lactose. Lactose is a sugar found in milk and other dairy foods.
Lactase is a digestive enzyme that breaks down lactose so the body can absorb it. Some people are born unable to make lactase. Others make less over time.
Lactose ferments in the colon and causes problems in people who do not make enough lactase.
This condition often starts when a person is a child. It is also more common in people who are Black and those of Ashkenazi Jew and Hispanic ancestry.
Things that may raise your risk are:
Problems often start 2 hours after eating a food that has lactose. Problems may be mild or severe. It depends on how much lactose was eaten.
It may cause:
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The doctor will ask about your symptoms and health history. A physical exam will be done.
These tests may be done to help make the diagnosis:
The doctor may also advise not eating lactose for a month to see whether symptoms stop.
There is no cure. Treatment is aimed at managing symptoms.
Foods with lactose often have nutrients the body needs, such as calcium. Foods can be eaten to replace them. Supplements are also an option.
A dietitian can help a person make these changes:
People who can only have small amounts of lactose can take lactase enzymes. It can be added as a liquid to foods. It can also be taken as a tablet before eating foods that have lactose.
There are no methods to prevent lactose intolerance.
American College of Gastroenterology
American Gastroenterological Association
Canadian Association of Gastroenterology
Dietitians of Canada
Lactose intolerance. National Institute of Diabetes and Digestive and Kidney Diseases website. Available at: https://www.niddk.nih.gov/health-information/digestive-diseases/lactose-intolerance. Accessed September 19, 2019.
Lactose intolerance in adults. EBSCO DynaMed website. Available at: https://www.dynamed.com/condition/lactose-intolerance-in-adults. Updated June 29, 2018. Accessed September 19, 2019.
Lactose intolerance in children. EBSCO DynaMed website. Available at: https://www.dynamed.com/condition/lactose-intolerance-in-children. Updated June 29, 2018. Accessed September 19, 2019.
Understanding food allergies and intolerances. American Gastroenterological Association website. Available at: https://www.gastro.org/practice-guidance/gi-patient-center/topic/lactose-intolerance. Accessed September 19, 2019.
Vandenplas Y. Lactose intolerance. Asia Pac J Clin Nutr. 2015 Dec;24 Suppl 1:S9-S13.
Last reviewed September 2019 by
EBSCO Medical Review Board Dianne Rishikof, MS, RDN, LDN, IFNCP
Last Updated: 9/2/2020