Lactose Intolerance Test

Also known as: lactose tolerance test.

What is a lactose intolerance test?

Lactose intolerance is the inability to digest the sugar found in milk. It’s a common medical condition. A lactose intolerance test is the medical test used to determine if an individual is lactose intolerant and, if so, just how severe the condition is.

What happens during the procedure?

Under medical supervision, the patient drinks a lactose-rich liquid. Two hours later, a blood test measures the glucose levels in the blood. If glucose has not gone up, it means that the individual is lactose intolerant.

Additionally a hydrogen breath test can be done to determine if a patient is lactose intolerant. During this test, the patient will drink a lactose containing liquid and then breathe into balloons at various intervals to measure how much hydrogen gas is in the breath.

Is any special preparation needed?

No special preparations are needed for this test.

What are the risk factors?

The test causes the symptoms of lactose intolerance, including diarrhea, nausea, cramps, bloating, gas and vomiting.

Reviewed by: Carrie Firestone Baum, MD

This page was last updated on: September 16, 2025 12:41 PM