Lactose Intolerance

Last Updated August 2021 | This article was created by editorial staff and reviewed by Beth Oller, MD


What is lactose intolerance?

Lactose intolerance is a condition that causes stomach discomfort. It’s your body’s dislike of the sugar contained in milk. This includes all dairy products. Lactose intolerance is not a milk allergy. It’s not a life-threatening problem. It is a common problem. Babies have the lactase enzyme, so they are not lactose intolerant (although premature babies may not have the enzyme). Lactose intolerance may first appear in children at the age of 3.

Symptoms of lactose intolerance

Symptoms include:

  • Nausea
  • Stomach cramps/pain
  • Bloating
  • Gas
  • Diarrhea

You may hear gurgling noises in your stomach.

What causes lactose intolerance?

Lactose intolerance is caused by a missing enzyme. It’s called lactase. Lactase lives in your small intestine. Some people don’t have it because of infection, Celiac disease, Crohn’s disease, or inflammatory bowel disease (IBD). In rare cases, it is hereditary.

How is lactose intolerance diagnosed?

The “milk challenge” is the easiest way to diagnose lactose intolerance. Avoid eating and drinking all dairy products for several days. This includes milk, ice cream, and cheese. Drink a glass of milk. If you have stomach problems an hour later, you are probably lactose intolerant. If you aren’t sure, see your doctor. Your doctor will ask you questions about your symptoms and your history with dairy products. If they are unsure, there are other tests, including:

  • A blood test to test for lactose intolerance or the gene. You will be asked to drink a beverage with lactose in it. Two hours later, your blood is drawn and sent to a lab.
  • A hydrogen breath test. This can be done in a hospital, lab, or your doctor’s office. You will be asked to drink a beverage that contains lactose. After 15 minutes, you’ll be asked to blow into balloon-like bags every 15 minutes. The air inside the bags will be tested for hydrogen. If your air contains a lot of hydrogen, you are probably lactose intolerant. The full test takes about 2 hours.
  • Stool acidity test (where you provide a stool sample). This is a common test for infants and young children.
  • Genetics test. This involves taking a sample of your genes through a blood or a saliva (spit) sample.
  • A surgical biopsy of your intestine. This is done at a hospital. It requires anesthesia (medicine that puts you into a deep sleep). Your doctor will make a small cut in your stomach near your small intestine. He or she will take a sample. It will be sent to a lab.

Can lactose intolerance be prevented or avoided?

You can reduce discomfort by doing the following:

  • Cut back on the amount of dairy you eat or drink. One serving of milk should be ¼ or ½ cup.
  • Have food in your stomach (not more dairy).
  • Wait several hours before having more dairy.
  • Choose foods with less lactose. Those include buttermilk and hard cheeses (cheddar, parmesan, Romano), ice cream, and goat cheese.
  • Substitute soy or nondairy products. Use a nondairy coffee creamer.
  • Take supplements that help you digest lactose. These are pills you can chew before you eat or drink dairy.
  • Look for lactose-free foods in the grocery store.
  • Eat yogurt (if you can). Yogurt helps with stomach upset.

Talk to your doctor about vitamin supplements. Eat foods that are naturally high in calcium. These include leafy greens, oysters, sardines, canned salmon, shrimp, and broccoli. Choose orange juice and cereals with added calcium.

Lactose intolerance treatment

There is no cure for lactose intolerance. Watch what you eat and drink to reduce stomach pain, gas, and diarrhea.

Living with lactose intolerance

Living with stomach pain, gas, and bloating is uncomfortable. To feel better, watch what you eat and drink. Limiting your dairy will make your feel more comfortable.

Questions to ask your doctor

  • Could gas, bloating, diarrhea, and pain be a sign of a serious condition?
  • Can I develop lactose intolerance later in life?
  • Can you build up a tolerance for lactose as you age?
  • Do I need to take a calcium supplement if I don’t have dairy in my diet?