Diagnosis of Lactose Intolerance

How do doctors diagnose lactose intolerance?

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. Other conditions, such as irritable bowel syndrome, celiac disease, inflammatory bowel disease, or small bowel bacterial overgrowth can cause symptoms similar to those of lactose intolerance.

Your doctor may ask you to stop eating and drinking milk and milk products for a period of time to see if your symptoms go away. If your symptoms don’t go away, your doctor may order additional tests.

Physical exam

During a physical exam, your doctor may

• check for bloating in your abdomen
• use a stethoscope to listen to sounds within your abdomen
• tap on your abdomen to check for tenderness or pain

What tests do doctors use to diagnose lactose intolerance?

Your doctor may order a hydrogen breath test to see how well your small intestine digests lactose.

Hydrogen breath test

Doctors use this test to diagnose lactose malabsorption and lactose intolerance. Normally, a small amount of hydrogen, a type of gas, is found in your breath. If you have lactose malabsorption, undigested lactose causes you to have high levels of hydrogen in your breath.

For this test, you will drink a liquid that contains a known amount of lactose. Every 30 minutes over a few hours, you will breathe into a balloon-type container that measures the amount of hydrogen in your breath. During this time, a health care professional will ask about your symptoms. If both your breath hydrogen levels rise and your symptoms get worse during the test, your doctor may diagnose lactose intolerance.