Understanding Lactose Intolerance

Lactose is the natural sugar present in milk and in foods made from milk, such as yogurt, ice cream and cheese. A person with lactose intolerance does not produce enough lactase enzymes to break down lactose in their small intestine.

Symptoms of lactose intolerance range from mild to severe depending on the amount of lactose consumed and the amount a person can tolerate.

Common symptoms of lactose intolerance include:

  • Gas
  • Bloating
  • Abdominal pain
  • Loose stool or diarrhea1

Generally, these symptoms occur between 30 minutes to 2 hours after consuming milk or milk products.

People with celiac disease may be lactose intolerant because their small intestine is damaged. They cannot break down lactose well. However, unlike gluten exposure in people with celiac disease, lactose does not damage your intestine.

Common Questions About Lactose Intolerance

Take-Home Messages

  • If you were recently diagnosed with celiac disease, you may have lactose intolerance.
  • If you have removed all the gluten from your diet and you are still having symptoms, you may have lactose intolerance.
  • There are several ways to test for lactose intolerance — a trial at home or the hydrogen breath test is the most common.
  • Keep a food diary or avoid lactose for a week to help you figure out if you have lactose intolerance. You may need to limit your intake of lactose while your intestine heals.
  • Lactose intolerance can usually be controlled on a low-lactose diet. Complete avoidance of lactose is usually not necessary.
  • For many, the ability to tolerate lactose often slowly returns as the intestine heals. This often allows most or all dairy products to be added back into one’s diet.
  • If you do not tolerate or do not like milk products, there are many dairy-free products to choose from that contain calcium. There are very few vitamin D-rich food sources in the American diet.
  • You may be asked to take calcium and vitamin D supplements if your low lactose diet does not provide enough of these nutrients.
  • As always, talk to your dietitian or doctor when making any changes in your diet to avoid missing any important nutrients.



  1. Lactose Intolerance. National Digestive Diseases Information Clearinghouse www.niddk.nih.gov. September 2021. Accessed March 3, 2022.
  2. Deng Y, Misselwitz B, Dai N, et al. Lactose intolerance in adults: biological mechanism and dietary management. Nutrients. 2015;7(9):8020-35.
  3. Diagnosis of Lactose Intolerance. National Digestive Diseases Information Clearinghouse. www.niddk.nih.gov. Accessed March 1, 2022.
  4. Eating, Diet, and Nutrition for Lactose Intolerance. National Digestive Diseases Information Clearinghouse. www.niddk.nih.gov. Accessed March 1, 2022.
  5. Dietary Guidelines for Americans 2020-2025. 9th Edition. www.dietaryguidelines.gov. Accessed March 1, 2022.

Revision Date: March 1, 2022
Editors: Elisabeth Moore, RD, LDN and Melinda Dennis, MS, RDN, LD