Understanding What is the sugar solution for SIBO? for Diagnosis and Diet

October 7, 2025 •

5 min read

Did you know that diagnosing Small Intestinal Bacterial Overgrowth (SIBO) often involves a breath test where you consume a specific sugar solution? This process is key to understanding what is the sugar solution for SIBO, which serves as both a critical diagnostic tool and a major dietary consideration for managing symptoms.

Quick Summary

This guide explains the specific sugar solutions—glucose and lactulose—used in SIBO breath tests and explores why dietary sugars must be managed to control bacterial overgrowth and minimize symptoms.

Key Points

Diagnosis vs. Diet: Sugar solutions are used diagnostically in breath tests (glucose or lactulose), but dietary sugars must be restricted during SIBO treatment to manage symptoms.
Glucose Test Specificity: A glucose breath test is best for diagnosing SIBO in the upper small intestine due to rapid absorption, but may miss distal overgrowth.
Lactulose Test Sensitivity: A lactulose test covers the entire small intestine but requires careful interpretation to avoid false positives caused by normal colonic fermentation.
Sugars Fuel Symptoms: Dietary fermentable carbohydrates, including fructose, sucrose, and polyols, feed overgrown bacteria and produce gas, worsening SIBO symptoms.
Dietary Management: Managing SIBO often involves a temporary low-FODMAP diet to limit fermentable sugars, which should be done under a practitioner's supervision.
Long-term Strategy: The aim is short-term sugar restriction to aid treatment, followed by gradual reintroduction of tolerated foods to support a healthy microbiome.

The Dual Role of Sugar in SIBO

Small Intestinal Bacterial Overgrowth (SIBO) is a condition where an excessive amount of bacteria, especially those typically found in the colon, colonize the small intestine. These bacteria feed on undigested carbohydrates, or sugars, that reach the small intestine, producing gases like hydrogen and methane that lead to common symptoms such as bloating, abdominal pain, and diarrhea. This makes understanding the role of sugar crucial for anyone dealing with SIBO, as it is involved in both the diagnosis and management of the condition. On one hand, specific sugar solutions are deliberately used to provoke a bacterial reaction during a diagnostic breath test, while on the other, dietary sugars are restricted to reduce symptoms.

The Sugar Solutions for SIBO Diagnosis

When a healthcare provider suspects SIBO, they often order a hydrogen and methane breath test. This non-invasive test requires the patient to drink a sugar solution (substrate) after a period of fasting. The test measures the levels of hydrogen and methane gases in the patient's breath at intervals over several hours. An early and significant rise in these gas levels can indicate bacterial fermentation in the small intestine, leading to a SIBO diagnosis. The choice of sugar substrate is a critical factor in the test's accuracy.

Glucose Solution: The Standard for Proximal SIBO

Glucose is a simple sugar that is absorbed very quickly and primarily in the first few feet of the small intestine. For this reason, a glucose breath test is highly specific for detecting SIBO located in the upper, or proximal, part of the small intestine. Because healthy individuals absorb glucose rapidly, little to no sugar should reach the far end of the small intestine or the colon, preventing false positives from normal colonic bacteria. A drawback, however, is that if the bacterial overgrowth is located farther down, in the distal small intestine, a glucose test may produce a false-negative result because the sugar never reaches the area of overgrowth. Diabetics are also advised to use an alternative substrate due to the effect on blood sugar levels.

Lactulose Solution: Comprehensive Small Intestine Coverage

Lactulose is a synthetic sugar that humans cannot digest or absorb. This allows it to travel the entire length of the small intestine and into the colon, feeding any bacteria present along the way. Because of this property, a lactulose breath test has a higher sensitivity for detecting SIBO in the distal small intestine, where glucose may not reach. The main disadvantage is that lactulose will always be fermented by bacteria once it reaches the colon, potentially causing a rise in gas levels that could be mistaken for SIBO, especially in patients with rapid transit times. Careful interpretation is key to differentiating a positive SIBO result from normal colonic fermentation.

Comparison Table: Glucose vs. Lactulose Breath Tests


Feature	Glucose Breath Test	Lactulose Breath Test
Substrate	Glucose (simple sugar)	Lactulose (synthetic sugar)
Absorption	Absorbed quickly and high up in the small intestine.	Not absorbed by the human body.
Coverage	Best for detecting SIBO in the proximal small intestine.	Detects SIBO anywhere in the entire length of the small intestine.
Specificity	High specificity, low risk of false positives from colonic bacteria.	Lower specificity; risk of false positives if normal colonic fermentation is mistaken for SIBO.
Sensitivity	May result in false-negatives if SIBO is in the distal small intestine.	Higher sensitivity for detecting overgrowth throughout the small intestine.
Taste	Generally preferred for its sweet taste.	Can have a syrupy taste and potentially cause more digestive discomfort during the test.
Patient Suitability	Unsuitable for patients with diabetes.	Safe for diabetic patients as it does not affect blood sugar.

The Role of Dietary Sugar in a SIBO Diet

For a person diagnosed with SIBO, the sugar solution is no longer a diagnostic tool but a dietary trigger. The bacteria overgrowth in the small intestine feeds on fermentable carbohydrates, a category that includes many dietary sugars. Restricting these foods is a cornerstone of SIBO management and can help reduce symptoms.

How Dietary Sugars Fuel Bacterial Overgrowth

When fermentable carbohydrates are not fully absorbed in the small intestine, they travel further down and are fermented by the overgrown bacteria. This process produces gas, leading to the characteristic bloating, pain, and other symptoms of SIBO. A diet low in fermentable sugars essentially starves the problematic bacteria, allowing for symptom relief.

Common Sugars and Sweeteners to Limit

High-Fructose Corn Syrup (HFCS): A common sweetener in processed foods and sodas that readily feeds bacteria.
Sucrose (Table Sugar): Excess intake provides fuel for the overgrowth and can be a trigger for symptoms.
Natural Sweeteners: Even seemingly 'healthy' options like honey, maple syrup, and agave are concentrated sources of sugar that can exacerbate SIBO.
Sugar Alcohols (Polyols): These low-calorie sweeteners (e.g., sorbitol, xylitol) are poorly absorbed and can trigger significant fermentation and gas production in people with SIBO.
Lactose and Fructose: These sugars are high in fermentable compounds (FODMAPs) and often restricted during a SIBO diet.

Navigating a SIBO-Friendly Diet

Managing your intake of fermentable sugars can be challenging, as they are found in many foods. For symptom control, many people follow a low-FODMAP diet, which limits specific types of fermentable carbohydrates. This approach is often temporary and guided by a healthcare provider or dietitian to ensure nutritional needs are met. The ultimate goal is to starve the overgrown bacteria and reduce symptoms without causing long-term dietary deficiencies.

Foods to Limit During Treatment:
- High-Fructose Corn Syrup and added sugars in sauces, dressings, and drinks.
- High-FODMAP foods like garlic, onions, certain fruits, and legumes.
- Sugar alcohols (polyols) used in sugar-free products.
- Lactose from dairy products, especially if intolerant.
Foods That Are Generally Well-Tolerated:
- Plain proteins like meat, fish, and eggs.
- Low-FODMAP fruits such as grapes, blueberries, and oranges.
- Starchy vegetables like potatoes, white rice, and quinoa.
- Healthy fats like olive oil and coconut oil.
- Ample water intake is vital for maintaining gut motility.

Conclusion: A Balanced Perspective on Sugar and SIBO

For those with SIBO, sugar represents a significant double-edged sword. It is an indispensable diagnostic tool in the form of glucose or lactulose solutions for breath testing, enabling accurate identification of bacterial overgrowth. At the same time, it is a primary culprit in fueling the bacterial fermentation that causes painful and uncomfortable symptoms. By understanding which sugar solutions are used for diagnosis and strategically managing dietary sugar intake, individuals can work with their healthcare providers to effectively treat SIBO and find relief. The goal is not permanent sugar restriction but a temporary, targeted dietary modification to complement antibiotic or herbal antimicrobial treatment. Successfully rebalancing the gut microbiome is the key to a long-term resolution of symptoms.

For more comprehensive information on SIBO, consider exploring authoritative sources like the Cleveland Clinic article on the condition.(https://my.clevelandclinic.org/health/diseases/21820-small-intestinal-bacterial-overgrowth-sibo)

Frequently Asked Questions

There are two main sugar solutions, or substrates, used in a SIBO breath test: glucose and lactulose. Glucose is rapidly absorbed and better for detecting overgrowth in the upper small intestine, while lactulose passes through the entire length, offering broader coverage.

Sugar makes SIBO symptoms worse because the overgrown bacteria in the small intestine feed on it through fermentation. This process produces excess gas (hydrogen and methane), which leads to symptoms like bloating, pain, and diarrhea.

No, natural sugars like honey, maple syrup, and agave nectar are not okay during SIBO treatment. They are concentrated fermentable carbohydrates that feed the bacteria and can exacerbate symptoms just like refined sugar.

The low-FODMAP diet is a temporary, restrictive eating plan that limits fermentable carbohydrates, including specific sugars and starches. This reduces the fuel available for bacteria and helps manage SIBO symptoms, but it is not a cure.

You do not necessarily have to avoid all sugar permanently. The goal is a temporary, strategic elimination phase, followed by careful reintroduction of small amounts of well-tolerated sweeteners under medical guidance.

The glucose test is not ideal for all cases because the sugar is absorbed so quickly in the upper small intestine. If the overgrowth is located farther down, the sugar may not reach it, resulting in a false-negative result.

You should be cautious with sugar-free products, as many contain sugar alcohols (polyols) like sorbitol or xylitol. These are poorly absorbed and can also be fermented by bacteria, triggering SIBO symptoms.

The restrictive phase of a SIBO diet, such as a low-FODMAP diet, is typically followed for a short duration, like 4-6 weeks, alongside other treatments. The goal is to gradually reintroduce foods to find individual tolerances.