Research suggests SIBO is underdiagnosed. You should be tested for it if you have ongoing bloating and bowel problems. Treatments for SIBO are available, so identifying it opens the door for symptom relief.
In this article, you’ll learn a little about each option, what to do before the test, and what to expect from the test itself.
Who Should Be Tested?
Experts recommend SIBO testing if you have chronic:
BloatingAbdominal painDiarrhea
This is because irritable bowel syndrome (IBS) can be misdiagnosed in people with these symptoms.
Testing is also recommended if you have:
Nutritional deficiencies Worsening Crohn’s disease, scleroderma, or chronic pancreatitis despite treatment Celiac disease symptoms despite a strict gluten-free diet
The diagnostic tests for SIBO are breath tests, jejunal aspiration, and a medication trial.
Breath Testing
Breath testing is non-invasive. It’s used fairly frequently as a way to look for SIBO.
When bacteria in the small intestine interact with sugar, they release hydrogen or methane. Those chemicals then come out in your breath.
For the test, you have a sugary drink and then have your breath checked periodically. Hydrogen before the 90-minute mark suggests SIBO.
Those bacteria belong in the large intestine, not the small one. It takes about two hours for the sugar to reach the large intestine. That’s why the cutoff is 90 minutes.
Despite wide use, some experts have concerns about the validity of SIBO breath tests. It yields many false-positive results. That especially true in people who digest food faster than average.
It also produces false negatives. That’s often because of gastroparesis (slow emptying of the stomach).
In addition, there’s no consensus on how best to perform the test. Nor is there agreement on exactly what amounts of gas should be present for a positive result.
Still, the simplicity and safety of the test make it a popular way to test for SIBO.
Before the Test
Testing should be done somewhere that tests for both hydrogen and methane. Your healthcare provider or the facility will tell you how to prepare.
Follow directions carefully so you get accurate results. Typical guidelines are:
In the month before: Do not use any colon cleansing products like what’s used before a colonoscopy. In the four weeks before: Don’t take any antibiotics or probiotics. In the week before: Don’t use laxatives, fiber supplements, or stool softeners. In the 48 hours before: Avoid high carbohydrate meals and snacks, especially whole grain bread or pasta. GERD medication for 48 hours before: If you take prokinetic medications (Cisapride, Motegrity) for gastroesophageal reflux disease (GERD), you may need to go off of it. In the 12 hours before: Don’t smoke, exercise, or eat/drink anything. This includes gum and candy.
During the Test
During the test, you may be asked to rinse your mouth with mouthwash. That kills any bacteria that may be present.
You’ll then give a baseline breath sample. Usually, that means blowing up a balloon. Then you’ll drink a small amount of sugary liquid.
Every 15 minutes, you’ll give them another breath sample. The test will last two to three hours, depending on the type of sugar used.
Jejunal Aspiration
A more accurate—but also more invasive—test is called jejunal aspiration. It takes place during an upper endoscopy procedure.
An upper endoscopy involves a long tube with a camera threaded down through your mouth and throat. It’s named for the middle section of your small intestine: the jejunum.
During the endoscopy, the practitioner can take a sample. It’s then cultured and evaluated for bacteria.
Jejunal aspiration has limits to its accuracy for SIBO. False negatives are possible when:
The sample is taken from an area where the bacteria aren’t overgrown. The sample isn’t large enough The culture used was the wrong one for your particular bacteria strainThe sample was tainted by bacteria in your mouth, on the instruments, or through poor handling.
Despite these limitations, many researchers consider jejunal aspiration the “gold standard” for SIBO testing.
Before the Test
Your healthcare provider or the testing center will tell you how to prepare. Those instructions will likely be similar to those for the breath test.
If you have gastroparesis, you may be told to follow a liquid diet for three days before the test.
During the Test
The test will take place either at your healthcare provider’s office or at a testing facility.
Monitors may be placed on your body so your provider can keep an eye on your breathing, heart rate, and blood pressure.
An IV will most likely be started. You’ll get a mild sedative to relax you. It may not put you fully out.
Next, a numbing anesthetic will be sprayed on your throat. Then a thin tube will be inserted down your throat.
You’ll be able to breathe but not talk. Your healthcare provider will then take a sample of fluid from your small intestine using an aspiration catheter.
Then the tube will be removed from your throat. After that, you may rest for a while to allow the anesthesia to wear off.
Because you’ll be sedated, you can’t drive yourself home afterward. For the rest of the day, keep your activity to a minimum.
You may have mild side effects such as:
GassinessBloatingCrampingSoreness in the throat area
If you experience any severe, unusual, or worrisome symptoms (vomiting or coughing up blood), contact your healthcare provider immediately.
Medication Trial
One way to check for SIBO is with a trial of SIBO medication. If symptoms quickly drop off, it suggests you have it.
The most common SIBO drug is Xifaxan (rifaximin). It’s an antibiotic. It’s different from most antibiotics, though.
Rather than being absorbed into your bloodstream, it acts directly on bacteria in your small intestine.
The medical community hasn’t yet set dosing standards for SIBO trials. But some healthcare providers follow the FDA guidelines for using Xifaxan to treat diarrhea-predominant IBS (IBS-D).
These guidelines recommend taking the medication for a two-week period, then repeating it for another one or two weeks.
This approach has limits, though.
There’s no guideline as to what’s considered a “good” response. If you don’t get enough to kill the bacteria, the trial may be inconclusive. Too much medication can mean side effects.
So this approach is a tricky one to gauge.
Summary
SIBO may be underdiagnosed. If you have ongoing bowel problems, you should be tested.
Three types of SIBO testing are used:
Breath tests for hydrogen or methaneJeujunal aspiration during upper endoscopyA trial of Xifaxan
Each approach has pros and cons for diagnosing SIBO.
A Word From Verywell
Researchers are working to better understand SIBO and how to diagnose it. Ideally, healthcare providers would be able to reliably detect not only the presence of bacteria but which specific type(s) you have.
If you have regular bowel problems that aren’t helped by treatment, talk to your provider about SIBO. They can help determine which test is right for you and get you started with diagnosis and treatment.
Abdominal painAbdominal distension (swelling)BloatingDiarrheaFlatulence (farting)
