Small Intestinal Bacterial Overgrowth (SIBO)

Up to 80% of people with IBS may actually have small intestinal bacterial overgrowth (SIBO). If you suffer from chronic bloating, excessive gas, or abdominal pain that worsens after eating, see the experts at Mirage Health in Chandler or Mesa, Arizona. Board-certified gastroenterologist Rajiv Sharma, MD, and the team diagnose and treat SIBO to relieve painful symptoms and restore long-term gut health. Schedule an in-person or telehealth appointment by phone or request one online today.

You've cut out gluten. Then dairy. Then anything with onions in it. You still bloat by mid-afternoon until your waistband hurts, and every test comes back normal.

That pattern has a name, and it's testable.

SIBO — small intestinal bacterial overgrowth — happens when bacteria that belong in your large intestine set up in your small intestine instead. They ferment food before you can absorb it. The gas has nowhere to go, so you swell.

Board-certified gastroenterologist Rajiv Sharma, MD, tests for SIBO, treats it, and works on why it happened — because SIBO that gets treated without that last step tends to come back. Mirage Health has offices in Chandler and Mesa and sees patients from across the East Valley.

The clock is the clue

Bloating that builds through the day points somewhere specific. Bloating that's constant usually doesn't.

Most people with SIBO describe the same arc. You wake up flat and your stomach feels fine. By late morning, breakfast is still sitting there and there's slight pressure. By mid-afternoon the waistband is tight enough that you unbutton in the car. By evening you're visibly distended, it hurts, and you skip dinner.

If your bloating is worse in the evening than in the morning, tell us at your first visit. It's one of the more useful things you can report.

Most people arrive having been told it's stress

Or IBS. Or that they should try eating more fiber.

Common symptoms:

• Bloating that starts after you eat and builds through the day
• Visible distension you can see in the mirror
• Excessive gas or belching
• Abdominal pain or cramping
• Diarrhea, constipation, or an alternating mix of both
• Nausea
• Fatigue and brain fog
• Food reactions that keep expanding until almost nothing feels safe

Some people also develop nutrient deficiencies. Bacteria in the small intestine consume vitamin B12 and interfere with fat absorption, which can show up as low B12, low iron, or low vitamin D on labs.

SIBO and IBS look nearly identical from the outside

A meaningful share of people diagnosed with IBS turn out to have SIBO driving the symptoms. Both produce bloating, pain, and unpredictable bowels.

The difference matters. SIBO has a specific test and a specific treatment. IBS is a diagnosis of exclusion. If you were handed an IBS diagnosis without anyone testing for bacterial overgrowth, that's worth revisiting.

Why it happens

Bacteria end up in the small intestine when something stops clearing them out. Usually one of these.

Slowed motility

Between meals, your small intestine runs a sweeping wave that clears leftover bacteria. Anything that dampens it — diabetes, hypothyroidism, prior gut infection, opioid medications, some antidepressants — lets bacteria accumulate.

Structural changes

Abdominal surgery, adhesions, strictures, or diverticula in the small bowel create pockets where bacteria collect.

Low stomach acid

Stomach acid kills bacteria before they get downstream. Long-term proton pump inhibitor use reduces that defense.

Food poisoning

A bad case of gastroenteritis can damage the nerves that control small intestine motility. Symptoms sometimes start weeks or months after the illness itself.

Finding your reason is the difference between a treatment that holds and one that unravels in three months.

How we test for it

Breath testing

SIBO is diagnosed with a breath test that measures hydrogen and methane. You drink a sugar solution, then breathe into collection tubes at set intervals. Bacteria in the small intestine ferment the sugar and produce gases that cross into your bloodstream and come out in your breath. A rise within a specific time window points to overgrowth.

The test requires diet prep the day before and a fast beforehand. We'll walk you through it.

Why the gas type matters

Hydrogen-predominant and methane-predominant overgrowth respond to different medications. Methane-predominant SIBO — now often called intestinal methanogen overgrowth, or IMO — skews toward constipation and needs a different regimen. Testing for both is what tells us which treatment to use.

Ruling out the rest

Celiac disease, pancreatic insufficiency, and inflammatory bowel disease can all produce similar symptoms. Depending on your history, Dr. Sharma may order bloodwork, stool studies, or an endoscopy alongside the breath test.

Treatment

Targeted antibiotics

Rifaximin is the most commonly used treatment for hydrogen-predominant SIBO. It stays largely within the gut rather than circulating through your body. Methane-predominant cases usually need a second agent added.

Nutrition that adds food back

We have registered dietitians on staff. This matters more in SIBO than in most GI conditions, because the most common self-treatment — eliminating more and more foods — often makes things worse. Our dietitians work on getting foods back in, not further restriction.

Motility support

If slow motility caused the overgrowth, killing the bacteria without addressing motility usually leads to relapse. A prokinetic medication after treatment can help keep the small intestine clearing.

Treating the cause

Thyroid function, blood sugar, medication review, prior surgical history. This is the part that determines whether you're back in six months.

Relapse is common with SIBO. We tell people that upfront rather than after the fact.

What your first visit looks like

You'll sit down with Dr. Sharma and go through your symptom history — when the bloating started, what you've already tried, what you've already cut out, what your previous doctors said. He'll examine you and decide which tests make sense.

Appointments are unhurried. Available in person in Chandler or Mesa, or by video from anywhere in Arizona.

Serving the East Valley

Our Chandler office sits at 2201 W. Fairview Street, just off the 101 and Chandler Boulevard. Our Mesa office is at 1910 S. Stapley Drive, near the 60.

Patients travel to us from across the East Valley:

• Chandler and Sun Lakes — 5 to 15 minutes from the Fairview Street office
• Mesa and Apache Junction — closest to the Stapley Drive office
• Gilbert — roughly 15 minutes to either location
• Tempe and Ahwatukee — a straight shot down the 101 or the 60
• Queen Creek and San Tan Valley — about 25 to 30 minutes to Mesa
• Scottsdale and Fountain Hills — the 101 runs directly to both offices

Video visits are available anywhere in Arizona if driving isn't practical. A lot of SIBO care — reviewing test results, adjusting treatment, checking in after a course of antibiotics — works fine over video.

Cost and payment

We accept most major insurance plans. For patients paying out of pocket, we post cash prices upfront so you can plan. CareCredit financing is available.

Questions patients ask before booking

Can SIBO go away on its own?

Rarely. The conditions that let bacteria accumulate — slowed motility, structural changes, low stomach acid — usually persist unless treated. Most people need treatment, and many need something in place afterward to prevent recurrence.

How long does SIBO treatment take?

A standard antibiotic course runs about two weeks. Symptom improvement often starts during that window. Longer-term work on motility and the underlying cause continues past it.

Is SIBO the same as candida or leaky gut?

No. SIBO is bacterial overgrowth in the small intestine and has a validated breath test. Candida overgrowth and leaky gut are different concepts with different levels of evidence behind them. If you've been told you have one of those without testing, a GI evaluation is worth doing.

Will I need a colonoscopy?

Not for SIBO diagnosis. Breath testing is the diagnostic tool. Dr. Sharma may recommend other procedures based on your history and symptoms.

Does insurance cover SIBO breath testing?

Coverage varies by plan. We can check your benefits before you test, and cash pricing is available if it isn't covered.

Can I get treated if I've already tried antibiotics and it came back?

Yes, and recurrence is common enough that we plan for it. Recurrent SIBO usually means the underlying cause wasn't addressed. That's where the evaluation focuses.

Do I need a referral to be seen?

Most PPO plans let you book directly with a specialist. Some HMO and Medicare Advantage plans require a referral from your primary care provider. Call us and we'll check your plan before you come in.

Bloated for months and told everything looks fine?

Get tested. Book online or call 480-210-3155.