Health Library

Lactose Intolerance

Lactose Intolerance

What is lactose intolerance?

Lactose intolerance is when your body can’t break down or digest lactose. Lactose is a sugar found in milk and milk products.

Lactose intolerance happens when your small intestine does not make enough of a digestive juice (enzyme) called lactase. Lactase is needed to break down the lactose in food so it can be absorbed by your body.

People who are lactose intolerant have unpleasant symptoms after eating or drinking milk or milk products. These symptoms include bloating, diarrhea, and gas.

Lactose intolerance is not the same thing as having a food allergy to milk.

Lactose intolerance is most common in Asian Americans, African Americans, Mexican Americans, and Native Americans.

What causes lactose intolerance?

Lactose intolerance can happen to children or adults. Here are some common causes of this condition:

  • Lactose intolerance often runs in families (hereditary). In these cases, over time a person’s body may make less of the lactase enzyme. Symptoms may occur during the teen or adult years.
  • In some cases the small intestine stops making lactase after an injury or after a disease or infection.  
  • Some babies born too early (premature babies) may not be able to make enough lactase. This is often a short-term problem that goes away.
  • In very rare cases some newborns can’t make any lactase from birth.

What are the symptoms of lactose intolerance?

Each person’s symptoms may vary. Symptoms often start about 30 minutes to 2 hours after you have food or drinks that have lactose.

Symptoms may include:

  • Belly (abdominal) cramps and pain
  • Nausea
  • Bloating
  • Gas
  • Diarrhea

How severe your symptoms are will depend on how much lactose you have had. It will also depend on how much lactase your body makes.

The symptoms of lactose intolerance may look like other health problems. Always see your health care provider to be sure.

How is lactose intolerance diagnosed?

Your health care provider will talk to you about your past health and family history. He or she will give you a physical exam.

You may be asked not to have any milk or milk products for a short time to see if your symptoms get better.

You may also have some tests to check for lactose intolerance. These may include:

  • Lactose tolerance test. This test checks how lactose is absorbed by your digestive system. You will be asked not to eat or drink anything for about 8 hours before the test. This often means not eating after midnight. For the test, you will drink a liquid that has lactose. Some blood samples will be taken over a 2-hour period. These will check your blood sugar (blood glucose) level. If your blood sugar levels don’t rise, you may be lactose intolerant.
  • Hydrogen breath test. You will drink a liquid that has a lot of lactose. Your breath will be checked several times. High levels of hydrogen in your breath may mean you are lactose intolerant.
  • Stool acidity test. This test is used for infants and young children. It checks how much acid is in the stool. If someone is not digesting lactose, their stool will have lactic acid, glucose, and other fatty acids.  

How is lactose intolerance treated?

There is no treatment that can help your body make more lactase. But you can manage your symptoms by changing your diet.

In the past, people who were lactose intolerant were told to stop taking dairy products. Today, health experts suggest you try different dairy foods and see which ones cause fewer symptoms. That way you can still get enough calcium and other important nutrients.

Lactose intolerance symptoms can be unpleasant, but they won’t hurt you. So try to find dairy foods that don’t cause severe symptoms.

Here are some tips for managing lactose in your diet:

  • Start slowly. Try adding small amounts of milk or milk products and see how your body reacts.
  • Have milk and milk products with other foods. You may find you have fewer symptoms if you take milk or milk products with your meals. Try eating cheese with crackers or having milk with cereal.   
  • Eat dairy products with naturally lower levels of lactose. These include hard cheeses and yogurt.
  • Look for lactose-free and lactose-reduced milk and milk products. These can be found at many food stores. They are the same as regular milk and milk products. But they have the lactase enzyme added to them.
  • Ask about lactase products. Ask your health care provider if you should take a lactase pill or lactase drops when you eat or drink milk products.

If you have trouble finding dairy products that don’t cause symptoms, talk to your health care provider. He or she can suggest other foods to be sure you get enough calcium. You may need to take calcium supplements.

Children with lactose intolerance should be seen by a health care provider. Children and teenagers need dairy foods. They are a major source of calcium for bone growth and health. They also have other nutrients that children need for growth.

Living with lactose intolerance

Lactose intolerance can affect you every time you eat a snack or meal. So you need to be careful about the foods you eat every day.

It’s important to read food labels. Lactose is often added to some boxed, canned, frozen, and prepared foods such as:

  • Bread
  • Cereal
  • Lunch meats
  • Salad dressings
  • Cake and cookie mixes
  • Coffee creamers

Check food labels for words that may mean a food has lactose in it, such as:

  • Butter
  • Cheese
  • Cream
  • Dried milk
  • Milk solids
  • Powdered milk
  • Whey

When should I call my health care provider?

Call your health care provider if you have trouble managing your symptoms. Some symptoms can be embarrassing. Your health care provider can work with you to help keep them under control.

Key points about lactose intolerance

  • Lactose intolerance is when your body can’t break down or digest lactose. Lactose is a sugar found in milk and milk products.
  • It happens when you don’t have enough of an enzyme called lactase. Lactase breaks down lactose in food.
  • The most common symptoms of lactose intolerance are belly cramps and pain, nausea, bloating, gas, and diarrhea.
  • There is no treatment that can help your body make more lactase.
  • You can manage your symptoms by changing your diet.

Next steps

Tips to help you get the most from a visit to your health care provider:
  • Before your visit, write down questions you want answered.
  • Bring someone with you to help you ask questions and remember what your provider tells you.
  • At the visit, write down the names of new medicines, treatments, or tests, and any new instructions your provider gives you.
  • If you have a follow-up appointment, write down the date, time, and purpose for that visit.
  • Know how you can contact your provider if you have questions.
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