Lactulose Breath Test for SIBO and Sugar Intolerance

If bloating, gas, belly swelling, diarrhea, or constipation keeps coming back, a breath test can help find out why. A lactulose breath test checks for small intestinal bacterial overgrowth (SIBO) by measuring gases in your breath. At our Temple City office you can take the test at home with the FoodMarble MedAIRE breath tester, which our office provides to you free of charge.

How a breath test works

When bacteria ferment sugar, they make hydrogen and methane. Your body does not make these gases. Some of the gas passes into your blood and leaves through your lungs, so it shows up in your breath. You drink a measured amount of a sugar, then breathe into the device at timed intervals. When the gas rises, and by how much, helps your doctor see where bacteria are fermenting the sugar.

Lactulose breath test for SIBO

Lactulose is a sugar that people cannot digest or absorb, so it travels through the small intestine toward the colon. If too many bacteria live in the small intestine, they ferment the lactulose early and the gas rises sooner. In the North American consensus guidelines, a hydrogen rise of 20 parts per million (ppm) or more above your starting level within 90 minutes counts as a positive test for SIBO. Methane at 10 ppm or higher points to intestinal methanogen overgrowth (IMO), which is linked to constipation.

Glucose breath test for SIBO

SIBO can also be tested with glucose. Glucose is absorbed quickly in the first part of the small intestine, so a glucose test mainly looks for overgrowth there. Lactulose travels farther, so it can pick up overgrowth in more of the small intestine, but fast movement through the gut can sometimes cause a misleading result. Each test has strengths and limits. Your doctor chooses the one that fits your symptoms and history.

The FoodMarble MedAIRE breath tester

We use the FoodMarble MedAIRE breath tester. It is a small handheld device that measures hydrogen and methane in your breath. In the US, MedAIRE is regulated by the FDA as a Class I medical device, and a physician uses it to help diagnose SIBO, IMO, and carbohydrate malabsorption.

• Your doctor prescribes the test, and our staff gives you the device and written instructions.
• You test at home. The FoodMarble app guides you and reminds you when to breathe into the device.
• Your results go to your doctor when the test is complete.
• The device can be used again for follow-up testing.

Cost: our office provides the device to you free of charge, and we bill your insurance for the test. Your out-of-pocket cost depends on your plan, such as your deductible or copay, so ask our staff about your coverage.

How to prepare

• 24 hours before: follow a plain diet. Foods that ferment easily, such as beans, high-fiber foods, and dairy, are usually avoided. We give you a handout at your appointment.
• Overnight: fast, usually 8 to 12 hours.
• Antibiotics: wait at least 2 weeks after your last course of antibiotics. Tell us if you took antibiotics recently, because the test may need to wait.
• Laxatives and gut-motility medicines: these are often stopped a week before if it is safe. Talk to us before stopping any medicine.
• Probiotics and acid reducers: ask us whether to pause them before the test.
• On test day: do not smoke, and avoid exercise during the test.

Follow the handout we give you if it differs from this list.

During the test

You drink the sugar solution, then breathe out gently for about 5 seconds into the device at the times the app tells you. Plan on about 2 to 3 hours for a SIBO test, and about 3 hours or more for a sugar intolerance test.

Your results

Your doctor reviews the results with your symptoms and health history. A breath test is one piece of the picture. If it shows SIBO, treatment may include an antibiotic such as rifaximin, diet changes, and treating the cause (see our SIBO article). After treatment, a repeat test can show whether the gas levels have improved.

Other sugar intolerance tests with the same device

The same device can test how your body handles other sugars that cause gas, bloating, and diarrhea. When a sugar is not fully digested or absorbed, it reaches the colon, where bacteria ferment it. We can test for:

• Lactose (milk sugar), for lactose malabsorption. Found in milk, ice cream, and soft cheeses.
• Fructose (fruit sugar), for fructose malabsorption. Found in fruit, honey, juice, and foods sweetened with high-fructose corn syrup.
• Sorbitol (a sugar alcohol). Found in sugar-free gum and candy and in fruits such as apples, pears, and prunes.
• Inulin (a fructan fiber). Found in onions, garlic, wheat, chicory root, and many foods with added fiber.
• Sucrose (table sugar), when we suspect congenital sucrase-isomaltase deficiency (CSID).
• Lactulose and glucose, for SIBO and IMO, as described above.
• Other sugars or foods, with a custom test your doctor sets up in the app.

Lactose, fructose, glucose, and lactulose have the most established testing protocols. Standard doses for sorbitol, inulin, and sucrose are still being studied, so we read those results together with your symptoms.

What breath tests cannot tell you

Breath tests do not diagnose celiac disease or food allergies, which need different tests.

Is a breath test right for you?

Ask us about it if you have:

• Bloating, gas, belly pain, diarrhea, or constipation that has no clear cause (see abdominal pain and bloating, chronic diarrhea, and constipation)
• Symptoms after milk, fruit, sugar-free foods, or high-fiber foods
• IBS-like symptoms (see IBS)
• Risk factors for SIBO, such as diabetes, scleroderma, or past stomach or intestinal surgery
• Symptoms that came back after treatment for SIBO

Interested in this test? Ask our staff or providers.

Learn more

• FoodMarble MedAIRE for physicians
• FoodMarble: breath testing and SIBO
• FoodMarble Food Intolerance Kit
• Unio Specialty Care: FoodMarble MedAIRE
• Hydrogen and methane based breath testing in gastrointestinal disorders: the North American consensus
• ACG clinical guideline: small intestinal bacterial overgrowth

Make an appointment

Our gastroenterologists in Temple City care for patients from Arcadia, San Gabriel, Pasadena, Monrovia, Monterey Park, and across the San Gabriel Valley. We accept most PPO plans (see accepted insurances), and our doctors speak English, Vietnamese, and Mandarin. Schedule an appointment or call 626-898-4560.

This article is for general education and is not a substitute for medical advice. Talk with your doctor about your own health.