- (910) 248-4853
- 250 MacDougall Dr. Seven Lakes, NC 27376
Small Intestinal Bacterial Overgrowth (SIBO) happens when bacteria that belong in the large intestine build up in the small intestine. This at-home breath test measures the gases those microbes produce — hydrogen, methane and, on some tests, hydrogen sulfide — to show whether overgrowth is present and which type you have.
This is one of the most common things I hear. When bloating builds through the day, when fiber and probiotics make you feel worse, or when IBS is the only explanation you’ve been given, SIBO is often part of the picture.
Removing foods only manages symptoms. The breath test shows whether bacteria are fermenting your food too early in the digestive tract — and which gas they produce, because each type needs a different approach.
Understanding the Test
Your body doesn’t produce hydrogen or methane on its own — only gut microbes do. After a short prep diet and an overnight fast, you drink a sugar solution (lactulose or glucose) and collect breath samples at set intervals over about two to three hours.
If bacteria in the small intestine ferment that sugar early, the gases show up in your breath sooner and at higher levels than they should. The pattern of gases over time tells us whether overgrowth is present and which type it is.
That distinction matters. Hydrogen, methane and hydrogen sulfide overgrowth behave differently and respond to different protocols — so the result directly shapes the diet, herbal or prescription approach we use.
What the test measures
Classic bacterial overgrowth
Methane overgrowth (IMO), linked to constipation
Measured on 3-gas tests only
Your gas levels before the test drink
Collected at set intervals over 2–3 hours
How early and how high gases rise
Could This Be You?
Flat in the morning, visibly distended by evening
Methane tends to slow things down; hydrogen often speeds them up
SIBO is a common finding in people told they have IBS
Bacteria may be feeding on them too early
Early fermentation produces gas higher in the gut
These are the symptoms many people never connect to SIBO — but that the breath test frequently helps explain.
Overgrowth affects absorption, not just digestion.
Bacteria in the small intestine can compete for nutrients like B12 and iron and interfere with fat absorption — which is why SIBO can show up as low energy, mood changes and stubborn deficiencies as often as gut symptoms.
What the Breath Test Reveals
The breath test doesn’t just say yes or no. The type of gas, how early it rises and how high it goes all shape the treatment plan — and give us a baseline to retest against.
The classic form. Bacteria ferment carbohydrates and produce hydrogen, often with bloating and looser stools.
Methane-producing archaea slow gut motility. Commonly linked to constipation and a heavy, full feeling.
Some bacteria convert hydrogen into hydrogen sulfide, which can irritate the gut lining. Only detected on 3-gas tests.
Each gas type responds to different diet, herbal and prescription strategies — so the result decides the protocol.
Your gas levels give us a starting point. Retesting after treatment confirms whether overgrowth has cleared.
Reading the Results
The small intestine should contain relatively few bacteria, while the large intestine is full of them. When you drink the test solution, it normally reaches the large intestine before significant gas is produced.
If gas rises early — before the sugar would reach the large intestine — it suggests bacteria are fermenting it higher up, in the small intestine. A sustained methane level, on the other hand, points to methane overgrowth regardless of timing.
Results are always interpreted alongside your symptoms and history. A borderline result with classic symptoms can be just as meaningful as a clearly positive one.
Illustrative only. Commonly used criteria: hydrogen rise of ≥20 ppm within 90 minutes; methane ≥10 ppm at any point. Your lab’s criteria may differ.
hydrogen, methane and hydrogen sulfide
of timed breath samples, at home
no needles, no clinic visit
a clear baseline to track progress
Two tests, two parts of the gut
Shows whether bacteria are overgrowing where they shouldn’t be, and which gas they produce
GI-MAP or BiomeFx map pathogens, parasites, yeast, diversity and gut-health markers
The Gut-Brain Connection
A breath test and a stool test answer different questions. The breath test looks at the small intestine; stool testing looks at the large intestine. Together they cover the whole digestive tract, so nothing is missed.
The goal isn’t to run every test — it’s to choose the ones that explain your symptoms and guide the right plan.
Breath Test vs. Stool Test
Stool samples reflect the large intestine. SIBO lives in the small intestine — which is why it needs a different test.
How It Works
No clinic visit and no needles. Here is exactly what working with Samantha looks like from start to finish.
01
We talk through your symptoms, history and health goals to confirm whether the SIBO breath test is the right starting point for you.
02
After your initial intake session, I order your breath test kit. It’s mailed to your home with full prep and collection instructions.
03
Follow a simple prep diet for one day, fast overnight, then drink the test solution and collect breath samples at set times.
04
We review your gas curves together and I build your protocol — diet, antimicrobials and motility support — then retest when it’s time.
years in practice
Why Work With Samantha
SIBO has a reputation for coming back. That’s usually because the overgrowth was treated, but the reason it developed — low stomach acid, slow motility, stress or nutrient gaps — was never addressed. I treat both, so your results last.
I’m Samantha Gilbert, a Certified Functional Nutrition Counselor with over 18 years of experience. The gut–brain connection is central to my practice, and many clients with anxiety, OCD, ADHD and depression find their gut is a missing piece.
Common Questions
It’s a non-invasive at-home test that measures hydrogen and methane — and on some tests hydrogen sulfide — in your breath after you drink a sugar solution. Because only gut microbes make these gases, rising levels early in the test point to bacterial overgrowth in the small intestine.
Preparation usually includes avoiding antibiotics and certain supplements for a period beforehand, following a simple low-fermentation diet the day before, and fasting overnight. Your kit includes full instructions, and I’ll review your medications and supplements with you before you start.
Absolutely—and this is often one of the most important things my clients learn. Around 90% of serotonin is produced in the gut, and dysbiosis disrupts that production. Elevated zonulin allows bacterial toxins to enter the bloodstream and cross the blood-brain barrier, contributing to neuroinflammation. H. pylori depletes zinc and B12, both of which are critical for mental health. In my practice, SIBO breath tests and GI Map and BiomeFx stool tests regularly uncover gut-related factors behind symptoms that have been treated as purely psychological for years.
Results are typically ready within 2 weeks after the lab receives your samples. We then book an appointment where I walk you through your gas curves and build your treatment plan
Often, yes. The breath test looks at the small intestine; a stool test like the GI-MAP with Zonulin or BiomeFx looks at the large intestine. Together they show the whole digestive tract.
Usually. Retesting after a round of treatment confirms whether the overgrowth has cleared and helps us decide when to move into the rebuilding and relapse-prevention phase.
The SIBO breath test ordered through my practice is generally an out-of-pocket cost. During your free discovery call I’ll walk you through current pricing and whether it’s the right starting test for you.
Book your free 20-minute discovery call with Samantha. We will talk through your symptoms and history and figure out whether GI Map testing is the right next step for you.