Could You Have Lactose Intolerance?

Medically Reviewed by Neha Pathak, MD on September 20, 2021
5 min read

Thirty minutes have passed since you ate a bowl of ice cream, and now your stomach is cramping and gassy. You feel like you might have diarrhea. Does this sound like you? Or, you had milk, mashed potatoes, or even candy almost 2 hours ago and have these symptoms. Does that sound like you? If either does, you could have lactose intolerance.

Lactose is the main sugar in milk and most other dairy products. Your small intestine makes the enzyme lactase to help you digest that sugar. When you're lactose intolerant, you don't make enough lactase to digest lactose well.

You can't cure lactose intolerance, but if you change what and how you eat, you may get rid of your symptoms.

Millions of Americans have symptoms of lactose intolerance:

You can use trial and error to find out what foods cause symptoms, and in what amount. And then check in with your doctor for a diagnosis. You may be sensitive to small amounts of foods that have lactose, or you may only have symptoms if you eat a lot of lactose foods. Your symptoms may be severe or mild. Lactose intolerance is different for everyone

There are four types of lactose intolerance, and they all have different causes.

  • Primary lactose intolerance is the most common form. Our bodies typically start a decline in lactase production as infants when we start switching to more solid food. As lactase levels decrease, dairy products become harder to digest. People with primary lactose intolerance make a lot less lactase. That makes dairy products hard to digest by adulthood. It’s caused by genes and is common among people of an African, Asian, Hispanic, Mediterranean, and southern European background. It’s less common if your heritage is from northern or western Europe.
  • Secondary lactose intolerance happens because of an injury, illness, or possibly a surgery. Any of these can affect your small intestine and cause you to make less lactase. Celiac disease and Crohn’s disease are two of the most common intestinal diseases linked to low lactase.
  • Developmental lactose intolerance happens in babies who are born prematurely. It usually goes away on its own, lasting for only a short time after birth.
  • Congenital lactose intolerance is very rare and happens when no lactase (or a very small amount of it) is produced by the small intestine from birth. It’s a genetic disorder, and both parents have to pass the gene on to their child.


Lactose intolerance is not the same as a dairy allergy. The two are often confused. If you have a dairy allergy, you’re allergic to certain proteins in milk and dairy products. Dairy allergy reactions can be life-threatening.

The symptoms of lactose intolerance are less severe than those of a dairy allergy. People with a dairy allergy need to avoid all foods and drinks that contain milk or other dairy products. If you’re lactose intolerant, you may be able to eat and drink small amounts of dairy products. How much varies from person to person. Lactose intolerance reactions aren’t life-threatening.

Milk and dairy products are the best-known lactose foods, but there are many others. Some nondairy products have a protein called casein, which can have traces of lactose. To avoid symptoms from lactose intolerance, read food labels carefully. When shopping or cooking, look for these ingredients that have lactose:

  • Curds
  • Dry milk solids
  • Milk
  • Milk byproducts
  • Dry milk powder
  • Whey
  • Casein

If you are highly sensitive to lactose, you may need to avoid foods such as:

  • Baked goods
  • Bread, baking, and pancake mixes
  • Breakfast cereals
  • Certain types of candy, such as milk chocolate
  • Instant foods (breakfast drink mixes, mashed potatoes, soups, and meal replacement drinks)
  • Margarine
  • Nondairy creamers (liquid and powdered)
  • Nondairy whipped topping
  • Processed meats (bacon, hot dogs, sausage, and lunch meats)
  • Protein and meal replacement bars
  • Salad dressing


Your doctor may ask you to keep a diary of the foods you eat, to note when you have symptoms, and to stop eating an offending food to see if your symptoms go away. To help make a diagnosis, some doctors simply look at your symptoms and whether avoiding dairy products for 2 weeks relieves them.

If uncertain, your doctor may do other tests to confirm the diagnosis, , such as:

Hydrogen breath test. Normally, people have very little hydrogen in their breath. If your body doesn't digest lactose, though, hydrogen builds in your intestines, and after a while, it's in your breath. This test measures how much hydrogen is in your breath after you have a lactose-loaded drink several times in a few hours. If your levels are high 3 to 5 hours later, your body does not digest lactose well.

Lactose tolerance test. When your body breaks down lactose, it releases sugar into your blood. This tests how much sugar is in your blood. After you fast, a small sample of blood is taken. Then, you drink a liquid that is high in lactose. Two hours later, you give another blood sample. Because lactose causes blood sugar levels to rise, your blood sugar levels in this sample should be higher. If you're lactose intolerant, you'll have just a low rise in blood sugar. But this test is rarely done anymore.

You can't change how well your body digests lactose, but you can cut or even stop your symptoms.

Talk with your doctor or a registered dietitian who can help you plan a healthy diet that keeps you feeling good. Keep a food diary to help you learn how much (if any) dairy you can eat without having symptoms. Many people don't need to stop eating all dairy.

If you make small changes in what you eat, you may be able to prevent symptoms by helping your body digest dairy foods easier.

Don't eat dairy alone. It's easier for your body to digest lactose when you eat it with other foods. So try having small amounts of milk or dairy foods with meals.

Choose easier-to-digest dairy products. Some people find it easier to digest dairy products like cheese, yogurt, and cottage cheese.

Use lactose-free or reduced-lactose milk and dairy products. You can find dairy products with most of the lactose removed, or lactase added, at many grocery stores.

Switch to dairy-free products. There are many non-dairy options, such as almond, rice, or soy milks. Special note about infants and young children: When babies have symptoms of lactose intolerance (although it's rare in children under age 6), pediatricians advise changing from cow's milk formula to soy milk formula until the symptoms go away, then slowly adding cow's milk formula and dairy products back into their diets.

Take a lactase enzyme replacement. These are available over the counter in pills or capsules. Take the advised dose with your first drink or bite of dairy to help prevent lactose intolerance symptoms.