Lactose Tolerance Tests
Reviewed
Also called: Hydrogen Breath Test, Oral Lactose Tolerance, Lactose Tolerance Serum Test, Lactose Intolerance Test, Lactose Breath Test, Disaccharide Absorption Test
Lactose tolerance tests measure your body's ability to break down lactose. There are two types: a hydrogen breath test that measures hydrogen gas in your breath, and a glucose blood test that measures blood glucose levels after drinking a lactose-containing liquid.
Specimen: For the hydrogen breath test: breath samples. For the glucose blood test: blood samples.
Why this test may be ordered
- Diagnose lactose intolerance
- Check for other health conditions that may cause similar symptoms, such as irritable bowel syndrome, celiac disease, small intestinal bacterial overgrowth (SIBO), Crohn's disease, or ulcerative colitis
Preparation and collection
Fast (not eat or drink) for eight to 12 hours before the test. Stop taking antibiotics for two to four weeks before the test. Do not smoke or exercise strenuously the day before the test. You may also need to stop taking certain medicines, such as laxatives, antacids, and stool softeners; tell your provider about everything you take and do not stop any medicines unless your provider tells you to. If you are having a breath test, you may need to brush your teeth or rinse your mouth shortly before the test.
For the hydrogen breath test, you breathe into a balloon-type container. For the glucose blood test, a health care professional takes a blood sample from a vein in your arm.
If you are lactose intolerant, you may feel cramps or bloating after drinking the lactose beverage. The supplied source states there are no other risks to having a hydrogen breath test. There is very little risk to having a blood test; there may be slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.
Understanding results
Your results will be interpreted by your healthcare professional. The following patterns are based on the test type.
- Hydrogen breath test: increased hydrogen level: An increased level of hydrogen and worsening symptoms after drinking lactose. Limitation: You may need more tests to figure out the cause of your symptoms. Next step: This probably means you have lactose intolerance.
- Hydrogen breath test: little or no increase in hydrogen level: Little or no increase in hydrogen after drinking lactose. Limitation: But sometimes you can have a negative result and still have lactose intolerance. You may need more tests to figure out the cause of your symptoms. Next step: This means your symptoms are probably not caused by lactose intolerance.
- Glucose blood test: glucose level did not increase: Your glucose levels did not increase after drinking lactose. Limitation: You may need more tests to figure out the cause of your symptoms. Next step: This probably means you have lactose intolerance.
- Glucose blood test: glucose level increased: Your glucose levels increased after drinking lactose. Limitation: But if you have diabetes, your blood glucose may increase even if you have lactose intolerance. You may need more tests to figure out the cause of your symptoms. Next step: This means your symptoms are probably not caused by lactose intolerance.
- If you are lactose intolerant, you may feel cramps or bloating after drinking the lactose beverage. The supplied source states there are no other risks to having a hydrogen breath test. There is very little risk to having a blood test; there may be slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.
- A negative result does not completely rule out lactose intolerance; further testing may be needed.
What to do next
If you are diagnosed with lactose intolerance, you should be able to manage your condition by limiting or avoiding foods with lactose, such as milk and cheese. Some people with lactose intolerance can have a limited amount of dairy without symptoms. Other people may need to avoid lactose altogether. Taking a supplement that contains lactase may also help manage your condition. Be sure to talk to your provider about planning your diet and/or taking lactase supplements.
- Diarrhea
- Abdominal (belly) pain
- Bloating
- Gas
- Nausea