Lactose Intolerance

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Definition & Facts

If you have lactose intolerance, you have digestive symptoms—such as bloating, diarrhea, and gas—after you consume foods or drinks that contain lactose. Lactose intolerance may affect your health if it keeps you from getting enough nutrients, such as calcium and vitamin D.

Symptoms & Causes

Symptoms of lactose intolerance may include bloating, diarrhea, gas, nausea, and pain in your abdomen. Lactose intolerance is caused by lactose malabsorption, a condition in which your small intestine makes low levels of lactase and can’t digest all the lactose you eat or drink.


To diagnose lactose intolerance, your doctor will ask about your symptoms, family and medical history, and eating habits. Your doctor may perform a physical exam and tests to help diagnose lactose intolerance or to check for other health problems.


You can manage lactose intolerance symptoms by changing your diet to limit or avoid foods that contain lactose. Some people may only need to limit lactose, while others may need to avoid lactose altogether. Using lactase products can help some people manage their symptoms.

Eating, Diet, & Nutrition

Talk with your doctor or a dietitian about changing your diet to help manage lactose intolerance symptoms and make sure you get enough nutrients. You may need to reduce the amount of lactose you eat or drink. Most people with lactose intolerance can eat or drink some lactose without symptoms.

Clinical Trials

The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) and other components of the National Institutes of Health (NIH) conduct and support research into many diseases and conditions.

This content is provided as a service of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), part of the National Institutes of Health. The NIDDK translates and disseminates research findings through its clearinghouses and education programs to increase knowledge and understanding about health and disease among patients, health professionals, and the public. Content produced by the NIDDK is carefully reviewed by NIDDK scientists and other experts.

The NIDDK would like to thank:
Rachel Fisher, M.S., M.P.H., R.D., NIDDK Office of Nutrition Research