Lactose Intolerance

Condition Basics

What is lactose intolerance?

Lactose intolerance is a problem that makes it hard to digest lactose. Lactose is a type of natural sugar found in milk and dairy products. This condition isn't the same thing as a food allergy to milk.

When lactose moves through the large intestine (colon) without being properly digested, it can cause gas, belly pain, bloating, and diarrhea. Some people who have lactose intolerance can't eat or drink any milk products. Others can eat or drink small amounts of milk products or certain types of milk products without problems.

What causes it?

Lactose intolerance occurs when the small intestine doesn't make enough of an enzyme called lactase. Your body needs lactase to break down, or digest, lactose. Sometimes the small intestine stops making lactase after a short-term illness, such as a stomach infection, or as part of a lifelong disease, such as cystic fibrosis.

What are the symptoms?

Symptoms of lactose intolerance can be mild to severe. Your symptoms may depend on how much lactase your body makes. Symptoms usually start 30 minutes to 2 hours after you eat or drink milk products.

Symptoms may include:

  • Bloating.
  • Pain or cramps.
  • Gurgling or rumbling sounds in your belly.
  • Gas.
  • Loose stools or diarrhea.
  • Throwing up.

How is lactose intolerance diagnosed?

A doctor can usually tell if you have lactose intolerance by asking questions about your symptoms. You may be asked to avoid dairy products for a short time to see if your symptoms improve. If symptoms improve, you may be asked to add small amounts of milk products to see if your symptoms return.

Sometimes doctors order tests to confirm the diagnosis. These simple tests check to see if you are digesting lactose normally.

  • Hydrogen breath test. This is the most accurate lactose intolerance test. If the hydrogen levels in your breath are high, you may have lactose intolerance.
  • Lactose tolerance test. This test measures your blood sugar after you eat or drink lactose. If your blood sugar levels don't rise, you may be lactose-intolerant. This test is not done for people who have diabetes.

These two tests usually aren't done for babies or very young children.

What can you do about lactose intolerance?

If you have lactose intolerance:

  • Limit the amount of milk and milk products in your diet.
  • Eat or drink milk and milk products that have reduced lactose. Try milk with reduced lactose, such as Lactaid milk.
  • Eat or drink other foods instead of milk and milk products. Try soy milk and soy cheese. And use nondairy creamers in your coffee.
  • Use lactase products. These are dietary supplements that help you digest lactose.
  • Try yogurt. Some people who are lactose-intolerant can eat some kinds of yogurt without problems, especially yogurt with live cultures.
  • Read food labels for lactose and for lactose's "hidden" names. These include dry milk solids, whey, curds, milk by-products, and nonfat dry milk powder.
  • Get enough calcium in your diet. Foods that have calcium include:
    • Broccoli, bok choy, kale, collard greens, mustard greens, and turnip greens.
    • Canned sardines.
    • Calcium-fortified orange juice.
    • Calcium-fortified soy milk and tofu.
    • Almonds.
    • Dried beans.


Current as of: September 20, 2023

Author: Healthwise Staff
Clinical Review Board
All Healthwise education is reviewed by a team that includes physicians, nurses, advanced practitioners, registered dieticians, and other healthcare professionals.