About Our Lactose Tolerance Test
Purpose of the Test
A lactose tolerance test, also commonly referred to as a lactose intolerance test, is used to help determine whether your body can properly digest lactose, a sugar found in milk and other dairy products. It is commonly used to help diagnose lactose intolerance in people who experience symptoms after consuming dairy. These symptoms often develop within 30 minutes to a few hours after consuming lactose-containing foods.
This test may be recommended if you have ongoing digestive symptoms such as bloating, gas, abdominal pain, or diarrhea after eating or drinking foods that contain lactose. It may also be used as part of an evaluation for malabsorption, a condition in which the body has difficulty breaking down or absorbing nutrients from food.
Because symptoms of lactose intolerance can overlap with other digestive conditions, testing can help clarify whether lactose is contributing to your symptoms.
What Does Our Lactose Tolerance Test Measure?
A lactose tolerance test measures how your body processes lactose after you consume a standard amount of it. Lactose is a type of sugar that must be broken down by an enzyme called lactase in the small intestine before it can be absorbed.
If your body does not produce enough lactase, lactose is not fully digested and instead passes into the large intestine. There, bacteria feed on the lactose (ferments), producing hydrogen gas and other byproducts (methane and carbon dioxide) that can lead to symptoms such as bloating, gas, nausea, and diarrhea.
This type of testing may also be called a lactose malabsorption test or lactose sensitivity test, depending on how it is used. There are two main ways to evaluate lactose tolerance in the body:
- Hydrogen breath test: This is the most commonly used test for lactose intolerance. It measures the amount of hydrogen in your breath before and after consuming lactose. Increased hydrogen levels suggest that lactose is not being properly digested and is instead being fermented by bacteria in the large intestine.
- Glucose blood test: A blood test measures changes in blood glucose levels after consuming a lactose product. When lactose is properly digested, it is broken down into glucose and galactose, which can be absorbed into the bloodstream. If blood glucose levels do not rise as expected, it may suggest that lactose is not being properly broken down.
The type of test used depends on your symptoms, medical history, and your provider’s recommendation. Blood testing is used less often than the breath test but may be recommended in certain situations.
When Should I Get a Lactose Tolerance Test?
Lactose tolerance testing may be recommended if you have symptoms that suggest your body is not properly digesting lactose. These symptoms often occur after consuming milk or other dairy products and can vary in severity depending on how much lactose is consumed, how well your body produces lactase, and your individual tolerance levels.
Many people wonder how to test for lactose intolerance or how to diagnose lactose intolerance when trying to understand symptoms after eating dairy. Symptoms typically develop within 30 minutes to a few hours after consuming lactose and may include a range of digestive discomfort that can vary from mild to more severe:
- Bloating
- Abdominal pain or cramping
- Excess gas
- Diarrhea
- Nausea
Because these symptoms can overlap with other digestive conditions, such as irritable bowel syndrome or food sensitivities, testing may be used to help confirm whether lactose intolerance is the cause.
In some cases, your provider may recommend testing to help rule out other causes of similar symptoms, such as celiac disease or small intestinal bacterial overgrowth (SIBO), especially if symptoms do not improve with dietary changes.
Testing may also be appropriate in situations where symptoms are persistent or unclear, including:
- People who regularly experience digestive symptoms after consuming dairy
- People who are unsure whether their symptoms are related to lactose or another condition
- People undergoing evaluation for malabsorption or other gastrointestinal disorders
Tests for lactose intolerance are not necessary for everyone. Many people can identify lactose intolerance based on their symptoms and dietary patterns. However, testing can be helpful when symptoms are ongoing, severe, or difficult to manage, or when a clear diagnosis is needed to guide dietary changes.
If you are unsure whether a lactose tolerance test is appropriate, a health care provider can help evaluate your symptoms, medical history, dietary patterns, and overall digestive health.
Finding a Lactose Tolerance Test
How to Get Tested
If lactose intolerance is a concern, your provider can help determine the most appropriate test based on your symptoms. In most cases, you’ll set up an appointment at a doctor’s office, hospital, or clinical laboratory.
Testing for lactose intolerance is typically done with a hydrogen breath test. After fasting 8-12 hours, a lactose solution is taken with breath samples collected every 15-20 minutes over a two-three hour period. This test measures how your body processes lactose over time.
In some cases, blood samples are taken after fasting and several times after partaking the lactose solution, generally 30, 60, 90, and 120 minutes after ingestion. These tests are used to evaluate changes in glucose levels after consuming the lactose solution.
Can I Take the Test at Home?
Options for a lactose intolerance test at home are limited compared to a clinical setting. Some providers offer a lactose intolerance test kit that allows you to collect breath samples and send them to a laboratory for analysis. Because a home lactose intolerance test may still require careful preparation, at-home options may still involve guidance from a health care provider or testing service.
How Much Does the Test Cost?
The cost of a lactose tolerance test depends on the type of test performed, where the test is conducted, and whether you have health insurance. Testing may be covered when ordered by a health care provider, though you may still be responsible for copays or deductibles.
Taking a Lactose Tolerance Test
A lactose tolerance test is usually performed using breath or blood samples collected over a period of time after you consume a drink containing lactose. The test is designed to measure how your body responds as it digests lactose.
Before the Test
Preparation is important to help ensure accurate results. You will typically need to fast overnight before the test, meaning you should not eat or drink anything except water. Also avoid excessive exercising.
Your health care provider may ask you to stop taking certain medications, such as antibiotics, laxatives, or antacids, for a period of time before testing. These medications can affect how your digestive system functions and may influence test results.
You may also be advised to avoid smoking, strenuous exercise, or certain foods before the test. Follow any specific instructions provided by your health care provider or testing facility.
During the Test
During a hydrogen breath test, you will be asked to drink a liquid that contains a standard amount of lactose. Breath samples are then collected at regular intervals by breathing into a collection device. The test measures hydrogen levels in your breath over time.
For a blood test, a sample is taken before you consume the lactose drink and then at set intervals afterward. These samples are used to measure changes in blood glucose levels.
The full testing process may take several hours, depending on the type of test being performed.
After the Test
After the test is complete, you can usually return to your normal activities unless your provider gives you other instructions.
Some people may experience temporary symptoms such as bloating, gas, or abdominal discomfort during or after the test, especially if they have difficulty digesting lactose.
Results are typically available within a few days. A health care provider will review your results and explain what they may indicate, as well as whether any follow-up or dietary changes are recommended.