What I need to know about

Lactose Intolerance

National Digestive Diseases 

Information Clearinghouse

What I need to know about

Lactose Intolerance
Contents

What is lactose?....................................................... 1

What is lactose intolerance? .................................. 1

Can anyone have lactose intolerance? .................. 4

What are the symptoms of lactose 

intolerance? ............................................................. 5

How does lactose intolerance affect 

my health?................................................................ 6

How does my doctor know if I have lactose 

intolerance? ............................................................. 6

How much lactose can I have?............................... 9

What can I do if I have lactose 

intolerance? ........................................................... 10

Eating, Diet, and Nutrition .................................. 10

Calcium and Vitamin D........................................ 13

How will I know if a food or medicine 

has lactose? ............................................................ 14

Points to Remember............................................. 18

Hope through Research ....................................... 19

Pronunciation Guide............................................. 20

For More Information .......................................... 20

Acknowledgments................................................. 21
1

What is lactose?

Lactose* is a sugar found in milk and milk 

products. The small intestine produces lactase,

an enzyme that breaks down lactose. The small 

intestine is an organ that breaks down the food 

you eat. Enzymes are proteins that help to cause 

chemical changes in the body.

*See the Pronunciation Guide for tips on how to 

say the words in bold type.

What is lactose intolerance?

Lactose intolerance means you have symptoms 

such as bloating, diarrhea, and gas after you have 

milk or milk products. 

If your small intestine does not produce much 

lactase, you cannot break down much lactose. 

Lactose that does not break down goes to your 

colon. The colon is an organ that absorbs water 

from stool and changes it from a liquid to a solid 

form. In your colon, bacteria that normally live in 

the colon break down the lactose and create fluid 

and gas, causing you to have symptoms. 
2

The causes of low lactase in your small intestine 

can include the following:

● In some people, the small intestine makes less 

lactase starting at about age 2, which may lead to 

symptoms of lactose intolerance. Other people 

start to have symptoms later, when they are 

teenagers or adults. 

● Infection, disease, or other problems that harm 

the small intestine can cause low lactase levels. 

Low lactase levels can cause you to become 

lactose intolerant until your small intestine heals. 

● Being born early may cause babies to be lactose 

intolerant for a short time after they are born. 

● In a rare form of lactose intolerance, the small 

intestine produces little or no lactase enzyme from 

birth. 

The digestive tract

Small 

intestine

Colon
3

Not all people with low lactase levels have 

symptoms. If you have symptoms, you are lactose 

intolerant.

Most people who are lactose intolerant can 

have some milk or milk products and not have 

symptoms. The amount of lactose that causes 

symptoms is different from person to person. 
4

People sometimes confuse lactose intolerance 

with a milk allergy. While lactose intolerance is a 

digestive problem, a milk allergy is a reaction by 

the body’s immune system to one or more milk 

proteins. If you have a milk allergy, having even a 

small amount of milk or milk product can be life 

threatening. A milk allergy most commonly occurs 

in the first year of life. Lactose intolerance occurs 

more often during the teen years or adulthood.

Can anyone have lactose intolerance?

Anyone can have lactose intolerance. In the 

United States, some people are more likely to be 

lactose intolerant, including 

● African Americans

● American Indians

● Hispanics/Latinos

● Asian Americans

People with European heritage are least likely to 

be lactose intolerant.
5

What are the symptoms of lactose 

intolerance?

Common symptoms of lactose intolerance include

● bloating, a feeling of fullness or swelling, in your 

belly

● pain in your belly

● diarrhea

● gas

● nausea

You may feel symptoms 30 minutes to 2 hours after 

you have milk or milk products. You may have 

mild or severe symptoms. 
6

How does lactose intolerance affect 

my health?

In addition to having unpleasant symptoms, you 

may have trouble getting enough nutrients, such as 

calcium and vitamin D. Milk and milk products are 

sources of calcium. Calcium is a mineral the body 

needs for strong bones and teeth. If you do not get 

enough calcium, over time your bones may become 

less dense and break easily.

How does my doctor know if I have 

lactose intolerance?

Your doctor will try to find out if you have lactose 

intolerance with the following:

● Medical, family, and diet history. Your doctor 

will ask you questions about your medical and 

family history, your diet, and your symptoms. 

● Physical exam. A physical exam may help your 

doctor find out if you have lactose intolerance or 

another problem. During a physical exam, your 

doctor usually

•	 checks for bloating in your belly

•	uses a stethoscope to listen to sounds within 

your belly

•	taps on your belly to check for tenderness or 

pain
7

After taking a history and completing a physical 

exam, your doctor may ask you to stop having milk 

and milk products to see if your symptoms go away. 

If your symptoms do not go away, your doctor 

might order the following tests: 

● Hydrogen breath test. This test checks the 

amount of a gas called hydrogen in your breath. 

Normally, a person’s breath only has a small 

amount of hydrogen after you eat lactose and 

the body breaks it down. Lactose that the body 

does not break down causes high amounts of 

hydrogen in the breath. For this test, you have a 

drink with a known amount of lactose. A doctor 

asks you to breathe into a balloon-type container 

that measures hydrogen. A doctor usually 

performs this test at a hospital, on an outpatient 

basis. Smoking and some foods and medicines 

may affect the results. Your doctor will tell you 

what foods and medicines you need to avoid 

before the test.
8

● Stool acidity test. If your body does not break 

down lactose, the lactose creates acid. The 

stool acidity test measures the amount of acid 

in the stool from a bowel movement. Doctors 

sometimes use this test for infants and young 

children. The doctor will give you a container to 

take home for catching and storing your child’s 

stool. You will need to return the sample to the 

doctor, and the doctor will send it to a lab for 

testing.
9

How much lactose can I have? 

Most people with lactose intolerance can eat or 

drink some lactose without symptoms. Different 

people can have different amounts of lactose. 

For example, one person may have severe 

symptoms after drinking a small amount of milk. 

Another person can drink a large amount without 

symptoms. Some people can easily eat yogurt and 

hard cheeses such as cheddar and Swiss, while 

other milk products cause them to have symptoms. 

Research suggests that many people could have the 

amount of lactose in 1 cup of milk in one sitting 

without symptoms or with only minor symptoms. 

You may be able to have more lactose if you have it 

with meals or in small amounts throughout the day. 

Many people who have lactose intolerance do not 

need to avoid milk or milk products completely. If 

you avoid milk and milk products altogether, you 

may take in less calcium and vitamin D than you 

need. 
10

What can I do if I have lactose 

intolerance?

If you have lactose intolerance, you can make 

changes to what you eat and drink. Some people 

may only need to have less lactose. Others may 

need to avoid lactose altogether. Using products 

that contain lactase helps some people. 

Eating, Diet, and Nutrition

Talk with your doctor about your dietary plan. A 

dietary plan can help you manage the symptoms 

of lactose intolerance and get enough nutrients. If 

you have a child with lactose intolerance, follow 

the diet plan that your child’s doctor recommends. 
11

Milk and milk products. You may be able to have 

milk and milk products without symptoms if you 

● drink small amounts of milk—half a cup or 

less—at a time

● drink small amounts of milk with meals, such as 

having milk with cereal or having cheese with 

crackers

● add small amounts of milk and milk products to 

your diet a little at a time and see how you feel

● eat milk products that are easier for people with 

lactose intolerance to break down:

•	 yogurt

•	hard cheeses such as cheddar and Swiss
12

Lactose-free and lactose-reduced milk and milk 

products. You can find lactose-free and lactosereduced milk and milk products at the grocery 

store. These products are just as healthy for you as 

regular milk and milk products. 

Lactase products. You can use lactase tablets and 

drops when you have milk and milk products. The 

lactase enzyme breaks down the lactose in food. 

Using lactase tablets or drops can help you prevent 

symptoms of lactose intolerance. Check with 

your doctor before using these products. Some 

people, such as young children and pregnant and 

breastfeeding women, may not be able to use these 

products. 
13

Calcium and Vitamin D 

If you are lactose intolerant, make sure you 

get enough calcium each day. Milk and milk 

products are the most common sources of 

calcium. Other foods that contain calcium 

include

● fish with soft bones, such as canned salmon or 

sardines 

● broccoli and other leafy green vegetables

● oranges

● almonds, Brazil nuts, and dried beans

● tofu

● products with the label showing added 

calcium, such as cereals, fruit juices, and 

soy milk

Vitamin D helps the body absorb and use 

calcium. Be sure to eat foods that contain 

vitamin D, such as eggs, liver, and certain kinds 

of fish, such as salmon. Also, being outside in 

the sunlight helps your body make vitamin D. 

Some companies add vitamin D to milk and 

milk products. If you are able to drink small 

amounts of milk or eat yogurt, choose those 

that have vitamin D added. 
14

Talk with your doctor about how to get enough 

nutrients—including calcium and vitamin D—in 

your diet or your child’s diet. Ask if you should 

also take a supplement to get enough calcium 

and vitamin D.

For safety reasons, talk with your doctor 

before using dietary supplements or any other 

nonmainstream medicine together with or in 

place of the treatment your doctor prescribes. 

Read more at www.ods.od.nih.gov and 

www.nccam.nih.gov.

How will I know if a food or medicine 

has lactose?

Lactose is in many food products and in some 

medicines.

Food Products

Lactose is in milk and all foods made with milk, 

such as

● ice cream

● cream 

● butter 

● cheese 
15

● cottage cheese

● yogurt 

Rarely, people with lactose intolerance are even 

bothered by small amounts of lactose. Some 

boxed, canned, frozen, packaged, and prepared 

foods contain small amounts of lactose. These 

foods include

● bread and other baked goods

● waffles, pancakes, biscuits, and cookies, and the 

mixes to make them

● prepared or frozen breakfast foods such as 

doughnuts, frozen waffles and pancakes, toaster 

pastries, and sweet rolls

● boxed breakfast cereals

● instant potatoes, soups, and breakfast drinks

● potato chips, corn chips, and other packaged 

snacks

● prepared meats, such as bacon, sausage, hot 

dogs, and lunch meats
16

● margarine

● salad dressings

● liquid and powdered milk-based meal 

replacements

● protein powders and bars

● candies

● nondairy liquid and powdered coffee creamers

● nondairy whipped toppings
17

Look for certain words on food labels. These 

words mean the food has lactose:

● milk

● lactose

● whey

● curds

● milk by-products

● nonfat dry milk powder

● dry milk solids—another name for dry milk 

powder
18

Medicines

Some medicines contain lactose, including 

● prescription medicines, such as birth control pills 

● over-the-counter medicines, such as products to 

treat stomach acid and gas 

These medicines most often cause symptoms in 

people with severe lactose intolerance. If you 

have lactose intolerance, ask your doctor if your 

medicines contain lactose. 

Points to Remember

● Lactose is a sugar found in milk and milk 

products. 

● Lactose intolerance means you have symptoms 

such as bloating, diarrhea, and gas after you have 

milk or milk products.

● Your doctor will try to find out if you have 

lactose intolerance with a medical, family, and 

diet history; a physical exam; and medical tests.

● Most people with lactose intolerance can eat or 

drink some lactose without symptoms.

● If you have lactose intolerance, you can make 

changes to what you eat and drink. Some people 

may only need to have less lactose. Others may 

need to avoid lactose altogether.
19

● Talk with your doctor about how to get enough 

nutrients—including calcium and vitamin D—in 

your diet or your child’s diet. Ask if you should 

also take a supplement to get enough calcium 

and vitamin D. For safety reasons, talk with your 

doctor before using dietary supplements or any 

other nonmainstream medicine together with or 

in place of the treatment your doctor prescribes.

● Lactose is in many food products and in some 

medicines.

Hope through Research

The National Institute of Diabetes and Digestive 

and Kidney Diseases’ (NIDDK’s) Division of 

Digestive Diseases and Nutrition conducts and 

supports basic and clinical research into digestive 

disorders such as lactose intolerance. 

Clinical trials are research studies involving people. 

Clinical trials look at safe and effective new ways to 

prevent, detect, or treat disease. Researchers also 

use clinical trials to look at other aspects of care, 

such as improving the quality of life for people 

with chronic illnesses. To learn more about clinical 

trials, why they matter, and how to participate, 

visit the NIH Clinical Research Trials and You 

website at www.nih.gov/health/clinicaltrials. For 

information about current studies, visit 

www.ClinicalTrials.gov.
20

Pronunciation Guide

calcium (KAL-see-uhm)

enzyme (EN-zym)

hydrogen (HY-droh-jen)

intestine (in-TESS-tin)

intolerance (in-TOL-ur-uhnss)

lactase (LAK-tayss)

lactose (LAK-tohss) 

supplement (SUH-pluh-muhnt)

For More Information

Academy of Nutrition and Dietetics

120 South Riverside Plaza, Suite 2000

Chicago, IL 60606–6995

Internet: www.eatright.org 

International Foundation for Functional 

Gastrointestinal Disorders

700 West Virginia Street, Suite 201

Milwaukee, WI 53204

Phone: 1–888–964–2001 or 414–964–1799

Fax: 414–964–7176

Email: iffgd@iffgd.org

Internet: www.iffgd.org 
21

Acknowledgments

Publications produced by the Clearinghouse are 

carefully reviewed by both NIDDK scientists and 

outside experts. This publication was originally 

reviewed by Rachel Fisher, M.S., M.P.H., R.D., 

and Jean Pennington, Ph.D., R.D., Division of 

Nutrition Research Coordination, NIDDK.

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Internet: www.digestive.niddk.nih.gov

The National Digestive Diseases Information Clearinghouse 

(NDDIC) is a service of the National Institute of Diabetes and 

Digestive and Kidney Diseases (NIDDK). The NIDDK is part of 

the National Institutes of Health of the U.S. Department of Health 

and Human Services. Established in 1980, the Clearinghouse 

provides information about digestive diseases to people with 

digestive disorders and to their families, health care professionals, 

and the public. The NDDIC answers inquiries, develops and 

distributes publications, and works closely with professional and 

patient organizations and Government agencies to coordinate 

resources about digestive diseases.

This publication is not copyrighted. The Clearinghouse 

encourages users of this publication to duplicate and distribute 

as many copies as desired.

This publication is available at www.digestive.niddk.nih.gov.

This publication may contain information about medications 

and, when taken as prescribed, the conditions they treat. When

prepared, this publication included the most current information 

available. For updates or for questions about any medications, 

contact the U.S. Food and Drug Administration toll-free at 

1–888–INFO–FDA (1–888–463–6332) or visit www.fda.gov. 

Consult your health care provider for more information.
NIH Publication No. 14–2751

May 2014

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