SIBO

Understanding SIBO - Small Intestinal Bacterial Overgrowth - Conventional Functional Medicine Approach

Yoon Hang Kim MD

16 Feb 2026 — 2 min read

What Is SIBO?

SIBO occurs when bacteria that normally live in the large intestine migrate and overgrow in the small intestine. The small intestine is designed to have relatively few bacteria. When excessive bacteria colonize this area, they ferment food prematurely, producing gas and triggering a cascade of digestive and systemic symptoms.

Common Symptoms	Risk Factors
Bloating and abdominal distension Excessive gas and belching Abdominal pain or cramping Diarrhea, constipation, or both Nausea and early satiety Brain fog and fatigue Nutrient malabsorption (B12, iron, fat-soluble vitamins)	Low stomach acid (hypochlorhydria) Chronic use of PPIs (acid blockers) History of food poisoning Impaired gut motility (e.g., diabetes, hypothyroid) Prior abdominal surgery or adhesions Immune deficiency or chronic stress Structural issues (strictures, diverticula)

How Is SIBO Diagnosed?

The most common test is a lactulose or glucose breath test. You drink a sugar solution and breathe into a collection device at regular intervals over 2–3 hours. Elevated levels of hydrogen or methane gas suggest bacterial overgrowth. Your provider may also order blood work to check for nutritional deficiencies associated with SIBO.

Types of SIBO: Hydrogen-dominant (often associated with diarrhea), Methane-dominant / IMO (intestinal methanogen overgrowth, often associated with constipation), and Hydrogen sulfide (newer area of research, linked to diarrhea and sulfur intolerance).

Conventional Functional Medicine Treatment Approach

SIBO treatment is typically a multi-phase process. A comprehensive approach addresses not just the overgrowth, but the underlying cause:

1. Reduce	Antimicrobial therapy (pharmaceutical such as Rifaximin, herbal, or both) to reduce the bacterial overgrowth. Treatment duration is typically 2–4 weeks.
2. Restore	Support digestion with enzymes, HCl supplementation if needed, and bile support. Repair the gut lining with targeted nutrients (e.g., L-glutamine, zinc carnosine).
3. Prevent Relapse	Address root causes: improve motility with prokinetic agents, manage stress, optimize diet, and restore the migrating motor complex (MMC).
4. Nourish	Replenish depleted nutrients. Consider a phased dietary approach (e.g., low-FODMAP transitioning to broader diet as tolerated).

What You Can Do

Space meals 4–5 hours apart to allow the migrating motor complex (MMC) to clear bacteria between meals.
Chew food thoroughly and eat mindfully — digestion starts in the mouth.
Manage stress through mind-body practices. Chronic stress impairs gut motility and immune function.
Avoid unnecessary antibiotics and prolonged PPI use when possible.
Follow your provider’s dietary guidance — dietary changes alone are rarely sufficient but are an important part of the plan.

Because I have found conventional functional medicine approach's success to be about 50% (about the same as conventional medicine success of SIBO), I have developed an approach that seems to be working better in my practice. I will upload that next - Root Cause Medicine approach to SIBO.

A note on expectations: SIBO can be stubborn and recurrence is common. Treatment often requires patience, persistence, and a willingness to investigate underlying causes. Every patient is unique — what works for one person may not work for another. We will work together to find the right approach for you.