by EBSCO Medical Review Board


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.

Risk Factors

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:

  • Cramping
  • Bloating
  • Belly pain
  • Gas
  • Diarrhea
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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:

  • Lactose breath hydrogen test to measure hydrogen in the breath after a person has lactose
  • Lactose tolerance test to check the sugar levels in the blood after a person has lactose

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.

Options are:

Dietary Changes

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:

  • Eating smaller amounts of milk or milk products with a meal. Many people can have 4 to 8 ounces of milk without having problems.
  • Eating dairy products that are easier to digest, such as hard cheeses and yogurt
  • Drinking lactose-free milk and lactose-reduced milk and milk products
  • Checking product labels for lactose in things like breads, baked goods, cereals, and salad dressing
  • Checking for words on product labels that refer to lactose, such as whey, curds, and milk by-products
  • Taking medicines that do not contain lactose


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: Accessed September 19, 2019.

Lactose intolerance in adults. EBSCO DynaMed website. Available at: . Updated June 29, 2018. Accessed September 19, 2019.

Lactose intolerance in children. EBSCO DynaMed website. Available at: . Updated June 29, 2018. Accessed September 19, 2019.

Understanding food allergies and intolerances. American Gastroenterological Association website. Available at: Accessed September 19, 2019.

Vandenplas Y. Lactose intolerance. Asia Pac J Clin Nutr. 2015 Dec;24 Suppl 1:S9-S13.

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