How to Test SIBO – Your Complete At-Home Guide

A SIBO screen is a non-invasive check for excess bacteria in the upper gut, measuring hydrogen and methane in your breath after a sugar solution. Under the North American Consensus (Rezaie et al., 2017), a hydrogen rise of 20+ ppm above baseline within 90 minutes is positive. 

Here is how to test SIBO from home.

Extra bacteria ferment carbohydrates and give off gases. The hydrogen reaches your lungs and leaves as you exhale. Each sample captures it at the lungs.

Two markers matter. Hydrogen flags an active case. CH4 comes from archaea; 15 to 30% of people are CH4-dominant. Excess CH4, now called IMO (intestinal methanogen overgrowth), tracks with constipation, while hydrogen-dominant cases cause diarrhea. Reading CH4 with hydrogen raises sensitivity and improves detection.

Yes, with limits. It is the most common method for diagnosing the condition (gold standard). 

Accuracy depends on the substrate. Against jejunal aspiration, glucose runs about 54.5% sensitive and 83.2% specific in patients; lactulose sits near 42% and 70.6%. The screen cannot always tell the upper gut from colon fermentation, the main source of false positives.

Three routes share the same thresholds; each option uses identical science.

Mail-in kits

The mail-in option ships to your door. You self-collect your readings and send them to a certified lab matching a clinic on substrate, fasting, intervals, and cutoffs. The lab measures both gases and returns your ppm readings; that analysis turns them into a curve.

Aspiration and culture

The historical benchmark is jejunal aspiration with quantitative culture. A count of at least 10^3 CFU/mL is positive, though clinicians rarely use it to diagnose routine cases now.

The right substrate depends on whether you need specificity or sensitivity.

• Glucose (75 g): absorbed in the upper bowel, so it is more specific with fewer false positives, but can miss colonization further down.

• Lactulose (10 g): not absorbed, so it covers the whole intestine and is more sensitive, with more false positives from colonic fermentation.

Some labs also run a lactose or fructose study for a suspected food intolerance, which is a separate question.

Preparation is identical whether you test by mail or in a clinic.

The day before your test

For 24 hours you eat a restrictive, low-fiber white diet, then fast 12 hours.

• White rice and white bread

• Plainly cooked chicken, turkey, or white fish

• Eggs, hard cheese, and clear broth

• Still water, per your kit's instructions

Skip fiber, fruit, vegetables, dairy beyond hard cheese, sweeteners, and heavy seasonings.

Medications and habits to pause

Certain products distort readings, so plan any medication change with a clinician.

• Antibiotics and probiotic supplements: about 4 weeks before

• Laxatives, fiber supplements, and prokinetics: about 1 week before

• Antacids such as Gaviscon: about 1 week before

• Smoking: about 1 week before

• Exercise and sleeping: not during the session, since both skew values

The protocol for how to test for SIBO at home matches a clinic's, no visit needed. Our own kit runs a baseline plus 9 collections every 20 minutes over 3 hours, reported in 24 to 72 hours.

• Order online: the kit ships to your door in about 2 to 5 days.

• Finish prep: complete the white diet, then the 12-hour fast.

• Take a baseline: provide the first sample into the collection bag or tube.

• Drink the glucose: consume the glucose solution as directed.

• Collect on schedule: one reading every 15 to 20 minutes across 2 to 3 hours, avoiding food, exercise, and heavy breathing.

• Mail it back free: seal each tube, add the prepaid label, and return the bag.

• Get your report: findings arrive within 24 to 72 hours, with an optional expert video.

Order your SIBO at-home test kit at IFDW. It uses a glucose substrate, ships to all 50 states, and needs no prescription. Read the test instructions first.

The positive cutoffs

These cutoffs are the most commonly used, from the North American Consensus and the 2020 ACG guideline (Pimentel et al.).

• Hydrogen positive: a rise of at least 20 ppm within 90 minutes.

• Methane positive (IMO): at least 10 ppm at any point.

• Hydrogen sulfide: the 3-gas panel cites 3 ppm, a manufacturer figure no consensus has validated.

Four common result patterns

Most reports match one of four shapes:

• Early rise: an early peak points to the upper bowel.

• Late rise: a peak after 90 minutes reflects the colon.

• CH4 elevation: a flat hydrogen line with high CH4 suggests IMO.

• Flat line: a true negative, or a masked hydrogen sulfide pattern a two-marker kit misses.

Your test cost depends on where you test and the panel you choose. Billing uses CPT code 91065.

• Mail-in kits: about $210 to $300, including lab and shipping.

• In-office visits: about $250 to $400.

• With coverage: often $20 to $100 out of pocket when approved.

Coverage varies. Medicare generally does not pay. 

Symptoms overlap with several related conditions, so patients often need other checks in a full evaluation. The Mayo Clinic and Functional Medicine labs use these adjuncts.

• Blood tests: screen for low vitamins and a fat-soluble deficiency (A, D, E, K) that poor absorption can cause. A B12 deficiency signals malabsorption.

• Stool tests: a stool study maps the microbiome and flags inflammation. Functional Medicine labs may also add a urine test, a urine panel showing microbial byproducts.

• Imaging: X-rays or an MRI are ordered only to rule out structural causes like strictures. X-rays and MRI do not detect it directly.

These checks separate the problem from other conditions with similar signs. IBS, or irritable bowel syndrome, brings the same bloating, yet irritable bowel syndrome has no microbial cause. Inflammatory Bowel Disease shows inflammation on biopsy; Inflammatory Bowel Disease needs clinical confirmation, not a home kit. A yeast problem, or SIFO, is fungal rather than bacterial, so yeast needs its own test.

Left alone, the condition can worsen and cause real complications. When microbes compete for nutrients, absorption drops.

• Malabsorption: damaged uptake in the gut lining reduces how much you take in.

• Vitamin deficiency: a fat-soluble vitamin shortfall is frequent, lowering vitamins A, D, E, and K.

• Weight change: ongoing malabsorption can drive unintended weight loss.

Treatment aims at eradication of the excess bacteria, not a quick fix. Antibiotics such as rifaximin are a common first-line medication, and eradication is usually paired with diet changes and nutritional support. No cure is guaranteed, and these complications are why early detection helps. 

Your medications and plan should come from a Gut Health Expert , who can request further analysis or a broader evaluation. Some medications target the archaea behind IMO.

A kit gives up supervision, so your diagnosis and treatment plan come from a clinician. Some situations need in-person care first.

• Alarm symptoms such as unexplained weight loss, bleeding, or severe pain

• An upcoming procedure or surgery

• Recent abdominal surgery, a known risk factor

• Diabetes, where the substrate needs medical oversight

• Significant underweight or malabsorption concerns

When any apply, book a Free Expert Call or see your provider. For more on diagnosing this, read our guide on how we diagnose SIBO.

Prep is where most mail-in screens go wrong:

• Skipping or shortening the 12-hour fast

• Taking probiotics or laxatives too soon

• Exercising or sleeping during the session

• Mistiming a reading past the 90-minute window

• Drinking the substrate can cause temporary bloating, nausea, or belly pain.

A negative report isn't the end. It is also a result. Symptoms may point to IBS, a food intolerance such as lactose, or another root cause on the gut-brain axis. Retesting, a GI Map test or a clinical opinion can help, and treatment should follow a complete diagnosis, not a single screen.

This article is for educational purposes only and does not replace medical advice from a licensed health professional. IFDW Health Services Inc. provides screening tools and information. For medical care, consult a qualified clinician.