How to properly prepare for the SIBO test (and avoid false negatives)

SIBO (Small Intestinal Bacterial Overgrowth) is a condition that may be affecting your digestive health without you even knowing it. If you're suffering from bloating, abdominal pain, gas, or even brain fog, you may have small intestinal bacterial overgrowth. But don't worry, there are specific tests to detect it! Today, I'll explain what they are, how they work, and which option is best for you.

What is SIBO and why is it important to detect it? 🤨

SIBO occurs when bacteria that normally live in the colon migrate to the small intestine. There, they ferment dietary carbohydrates, producing gases such as hydrogen, methane, and hydrogen sulfide. This can lead to symptoms such as:

1. Abdominal bloating (even after drinking water 💦)
2. Digestive pain or discomfort 🤕
3. Diarrhea, constipation, or both 💩
4. Fatigue and brain fog 🧠
5. Reflux and frequent burping 🤢
6. Food intolerances (gluten, lactose, FODMAPs) 🥛🍞

Since these symptoms can be confused with other digestive disorders, performing a specific test is crucial for an accurate diagnosis and to avoid false negatives.

🔬 Main tests to diagnose SIBO

1️⃣ SIBO Breath Test ✅ (Fast, affordable, and non-invasive)

It is the most commonly used test and measures the gases produced by bacteria in the small intestine, mainly hydrogen (H₂) and methane (CH₄) , which are expelled through the breath.

📌 How is it done?

1. Follow a low-residue preparatory diet for 24 hours.
2. Fast for 12 hours before the test.
3. Drink a solution of glucose or lactulose (which serves as food for bacteria).
4. Blow into collection tubes every 15-20 minutes for 2-3 hours .
5. Analyze breath gas levels to determine if SIBO is present.

📊 How to interpret the results of the breath test?

✔ Hydrogen SIBO (elevated H₂) → Indicates rapid bacterial fermentation in the small intestine, primarily associated with diarrhea, bloating, and gas . Detected with glucose or lactulose solution .

✔ Methane SIBO (elevated CH₄) – SIMO → Not SIBO per se, but an overgrowth of methanogenic archaea , which consume hydrogen and convert it into methane. Associated with constipation, severe bloating, and difficulty passing gas . It can be treated with glucose or lactulose, but sometimes requires specific approaches to treatment.

✔ Hydrogen sulfide SIBO (elevated H₂S) → More difficult to diagnose because it isn't always measured by standard tests. Causes severe diarrhea, foul-smelling stools, and possible neurological symptoms such as fatigue and brain fog.

🔹 Advantages of the breath test:
✅ Non-invasive, simple and accessible.
✅ It can be done at home or in a clinic.
✅ Detects small intestinal overgrowth without the need for more complex testing.

🔹 Disadvantages:
❌ Possible false negatives if intestinal transit is too rapid or if the type of gas is not measured correctly.
❌ The test cannot accurately pinpoint the exact location of the overgrowth . Therefore, when there is a late peak of gas, it cannot differentiate between:

🔹 A SIBO located in the final part of the small intestine.

🔹 Normal fermentation or dysbiosis in the large intestine.

❌ It may be less effective in cases of hydrogen sulfide SIBO , since some tests do not measure this gas.

2️⃣ Small bowel aspiration 🏥 (More accurate test, but invasive and expensive)

This technique involves introducing an endoscope into the small intestine to extract a fluid sample and analyze the amount of bacteria present.

📌 Pros:
✔ It is the most accurate method, as it detects bacteria directly in the small intestine.
✔ Allows you to identify what type of microorganisms are present.

📌 Cons:
✖ Invasive and expensive procedure.
✖ Not accessible in all medical centers.
✖ It may miss infections in more distal parts of the intestine.

It is reserved for cases in which the breath test is inconclusive and other pathologies are suspected.

3️⃣ Urine Organic Acid Analysis 🔬 (Indirect Assessment of Bacterial Overgrowth)

This test analyzes certain metabolites in urine that may be indicative of abnormal bacterial fermentation in the intestine.

📌 Pros:
✔ It can provide information on intestinal dysbiosis in general.
✔ It is non-invasive and easy to perform.

📌 Cons:
✖ It is not specific for SIBO, it only indicates an imbalance in the microbiota.
✖ It can be influenced by other factors such as diet or individual metabolism.

It is useful as a complement to other tests, but is not recommended as the sole diagnostic tool for SIBO .

Which test is best for you?

For most people, the lactulose breath test is the best option, as it covers the entire small intestine and can detect overgrowth anywhere. If you have persistent digestive symptoms, it's an excellent diagnostic tool.

🫁 How to prepare for the SIBO breath test?

To obtain accurate results and avoid false positives or negatives, follow these guidelines before testing:

📅 1 week before:
✔ Discontinue probiotics, prebiotics, and digestive supplements.
✔ Avoid laxatives, prokinetics, and drugs that affect intestinal motility (consult your healthcare professional).
✔ If you have taken antibiotics, osmotic laxatives, enemas, or had a colonoscopy in the last 4 weeks , wait before taking the test.

🍽 24 hours before: Special diet
✅ You can eat: Meat, fish, eggs, white rice, light meat broth, Serrano ham, olive or coconut oil, black coffee, black tea, and unsweetened infusions.
🚫 Avoid: Dairy, fruits, vegetables, legumes, whole grains, bread, pasta, carbonated drinks, alcohol, and juices.

⏳ 12 hours before: Total fast
✔ Only still water allowed.
❌ Do not chew gum or suck on candy.

🚭 Test day
📌 Oral hygiene: Brush without toothpaste and rinse with sorbitol-free chlorhexidine or just water.
📌 Avoid: Smoking, exercising, chewing gum, wearing strong perfumes, or talking during the test.
📌 During the test: Remain still, follow the instructions, and blow into the tubes as directed.

What to do if the result is positive?

If the test confirms SIBO, the next step is to address treatment, which may include:

✅ Personalized diet: Adapt your diet to a low-FODMAP or evolutionary anti-inflammatory approach by reducing the foods that make you feel worse.

✅ Mucosal treatment: Repair gastric mucosa as a first step before administering herbal medicine or antibiotics (especially if the mucosa is very irritated)

✅ Phytotherapy or antibiotics: Use antimicrobial plants or specific antibiotics such as rifaximin.

✅ Digestive support: Enzymes (with betaine and pepsin, if hypochlorhydria is present) and probiotics depending on the type of SIBO.

✅ Nervous system regulation: Chronic stress can perpetuate SIBO, so working on emotional management is key.

Conclusion 🧑⚕️✨

Detecting SIBO early is crucial to improving your digestive health and preventing symptoms from affecting your daily well-being. The breath test is the most accessible and noninvasive option for most people, but it's important to follow the preparation recommendations to obtain reliable results. If the diagnosis is positive, a comprehensive approach combining a proper diet, mucosal treatment, herbal medicine, and stress management will be essential to restoring intestinal balance. Remember, every step toward a clear diagnosis and appropriate treatment brings you closer to your complete well-being! 🌱💪

If you want to address your digestive problems at their root, schedule your appointment here now.