Lactose Intolerance

Lactose intolerance is the inability or insufficient ability to digest lactose, a sugar found in milk and milk products. Lactose intolerance is caused by a deficiency of the enzyme lactase, which is produced by the cells lining the small intestine. Lactase breaks down lactose into two simpler forms of sugar called glucose and galactose, which are then absorbed into the bloodstream.

Not all people with lactase deficiency have digestive symptoms, but those who do may have lactose intolerance. Most people with lactose intolerance can tolerate some amount of lactose in their diet.

People sometimes confuse lactose intolerance with cow milk allergy. Milk allergy is a reaction by the body’s immune system to one or more milk proteins and can be life threatening when just a small amount of milk or milk product is consumed. Milk allergy most commonly appears in the first year of life, while lactose intolerance occurs more often in adulthood.


Symptoms of lactose intolerance include:

  • Abdominal pain or discomfort
  • Bloating
  • Diarrhea
  • Gas

Risk Factors

Risk factors for developing lactose intolerance include:

  • Age: adults and older adults
  • Ethnicity: African American, American Indian, Asian and Hispanic
  • Genetics: a parent who is lactose intolerant
  • If you have or have had one of the following: celiac disease, Crohn’s diease, chemotherapy, or severe diarrheal illness

When to See a Doctor

Occasional abdominal distress such as cramping, bloating, or diarrhea may result from a number of causes and often resolves on its own. Effective treatments are available for lactose intolerance. If your symptoms have not resolved within a few days, are persistent, or if they recur, it’s time for a thorough evaluation and consultation with a specialist.

Treatment Options

Treatment options for individuals with lactose intolerance vary and may include following a special diet, free of lactose.


Lactose intolerance cannot be prevented but its’ symptoms and effects can be managed with dietary changes.

Learn More

Learn more about lactose intolerance with resources from the National Institutes of Health

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