Hydrogen Sulfide SIBO: Symptoms, Testing, and How to Reduce Excess H₂S
What is Hydrogen Sulfide SIBO?
Hydrogen sulfide SIBO (H₂S SIBO) is a subtype of Small Intestinal Bacterial Overgrowth (SIBO) in which bacteria produce excessive hydrogen sulfide gas in the small intestine. Hydrogen sulfide is a sulfur-containing gas that can cause symptoms distinct from typical hydrogen or methane SIBO (IMO) because it may not show up on standard breath testing, and is instead inferred based on symptom patterns and less common testing approaches.
Why Hydrogen Sulfide Is Different from Other SIBO Types
Hydrogen sulfide is a gas produced by certain bacteria (known as sulfur-reducing bacteria) as they metabolise sulfur-containing amino acids. While small amounts of hydrogen sulfide are normal and even play roles in cell signalling, excess production can contribute to gastrointestinal symptoms such as bloating, diarrhea, gas with a rotten-egg odor, abdominal discomfort, and sometimes systemic effects like fatigue.
Because standard breath tests measure hydrogen and methane — not yet hydrogen sulfide — this subtype can be missed unless more specialised testing is used. More on the Trio-Smart test below.
Who is at Risk for Hydrogen Sulfide SIBO?
While SIBO can affect anyone, certain groups may be more predisposed. Individuals diagnosed with Irritable Bowel Syndrome (IBS) or Ulcerative Colitis are at higher risk for developing SIBO, including the Hydrogen Sulfide variant. Notably, less than 5% of all SIBO cases are attributed to hydrogen sulfide overgrowth, making it relatively rare.
Common Symptoms of Hydrogen Sulfide SIBO
Symptom patterns overlap with other SIBO subtypes, but signs that hydrogen sulfide production may be prominent include:
Bloating and abdominal gas
Frequent diarrhea or alternating diarrhea/constipation
Nausea or food intolerances
Sulfur-smelling (rotten egg) flatulence or belching
Bowel urgency after meals (“the runs”)
Occasional systemic symptoms like fatigue or brain fog
These symptoms are not exclusive to hydrogen sulfide SIBO, but when the gas smell and diarrhea are prominent, it can raise suspicion.
Why Hydrogen Sulfide Is Hard to Diagnose
As mentioned above, standard SIBO breath testing measures hydrogen and methane after ingestion of a sugar solution, but it does not detect hydrogen sulfide gas reliably, which makes diagnosis challenging. A flat-line result (no significant rise in hydrogen or methane) on a breath test sometimes raises the possibility of hydrogen sulfide, but this is not definitive.
This means functional health practitioners often use symptom patterns, comprehensive history, and advanced testing (stool microbiome, GI-MAP) to infer H₂S overproduction.
The Trio-Smart test is currently the only test that measures Hydrogen Sulfide (H₂S) gas directly, and it is only available in the United States; or in Canada if you have a doctor’s referral.
If a SIBO breath test yields negative results, it's crucial to explore other potential medical conditions. These include inflammatory bowel disease (Ulcerative colitis or Crohn’s disease), collagen-based disorders like Ehlers Danlos Syndrome, Celiac disease, parasitic infections, Small Intestinal Fungal Overgrowth (SIFO), Helicobacter pylori infection, and more.
Bacteria Strains and Hydrogen Sulfide Production
The bacteria Klebsiella, Citrobacter, E. coli, Proteus, Desulfovibrio piger, Bilophila wadsworthia, Fusobacterium varium and Pseudomonas aeruginosa are amongst those commonly associated with digestive issues and hydrogen sulfide production.
To thoroughly assess their presence and potential impact on your digestive health, I suggest doing a GI-MAP test or any other type of Complete Microbiome Mapping. These tests provide comprehensive insights into the composition of your gut microbiome, aiding in the identification of specific bacteria and their potential implications for your digestive function.
Treatment Options for Hydrogen Sulfide SIBO
Allopathic treatment for SIBO typically involves antibiotic therapy to eradicate the overgrowth of bacteria in the small intestine. Natural approaches also exist, with a focus on a holistic treatment plan incorporating herbal supplements, biofilm disruptors, and dietary modifications tailored to each patient's health history and laboratory results.
In my practice I exclusively work with herbals but can work in tandem with your doctor if you prefer to use antibiotics. The most common substances used are Bismuth, Uva Ursi, oregano oil, and the antibiotic Rifaximin. See more helpful supplements below.
There is also clinical evidence for the use of High-dose MSM, which you can read about in my article.
Dietary Approaches for Managing H₂S Symptoms
Diet plays a central role in symptom management but should be personalised. A short-term, low-sulfur diet (reducing high-sulfur foods like garlic, onions, eggs, red meat, and cruciferous vegetables) can help reduce food for H₂S-producing bacteria and provide symptom relief while underlying imbalances are addressed. Diet alone is often insufficient as it does not address the overgrowth directly.
Note that “traditional” SIBO diets (like the low-FODMAP diet) do not effectively address sulfur overproduction. All these types of diet are meant for short-term use only, as overly restrictive diets can reduce nutrient diversity and harm the microbiome long-term. Because many sulphur-rich foods are also nutritious, the goal is not permanent avoidance but strategic reduction while working on root causes. I do not recommend going longer than 2 weeks on a low-sulfur diet.
Supplements and Targeted Support
Certain supplements may help manage hydrogen sulfide production or support gut balance. Note that data is currently limited and most evidence is extrapolated from microbiome science and small studies, not large RCTs.
Bismuth compounds: Used to bind hydrogen sulfide and reduce its production; research shows bismuth can markedly decrease H₂S release in the colon.
Molybdenum: A trace element involved in sulfur metabolism; may support enzymatic breakdown of excess sulfide in some individuals.
Probiotics: Some strains (e.g., Lactobacillus plantarum, Bifidobacterium infantis) may help modulate microbial balance and reduce H₂S production.
Soluble fibre (like psyllium): May help by reducing free sulfide gas through increased fecal mass and water content, potentially trapping gas.
Butyrate support: Short-chain fatty acids support colonocyte function and may improve microbial balance.
Always integrate supplements under guided practitioner supervision, especially with complex dysbiosis cases.
Complications associated with treatment for hydrogen sulfide SIBO include die-off reactions and digestive symptoms exacerbation.
Supporting Digestion and Root Causes
Improving digestion and motility supports overall gut microbiome balance and can reduce conditions that favour excessive H₂S production. This includes:
Supporting stomach acid and enzyme production to improve protein digestion
Addressing delayed motility with prokinetics if needed
Treating other underlying conditions such as other gut infections, motility disorders, or nutrient deficiencies
This addresses not just symptoms but drivers of dysbiosis.
Hydrogen sulfide SIBO presents unique diagnostic and management challenges because a) it is often not detected with standard tools and b) dietary sulphur is abundant in many nutritious foods. A targeted, balanced plan incorporating symptom management, dietary adjustments, selective supplements, and comprehensive digestion support tends to be most effective. By working closely with a knowledgeable health practitioner, you can achieve symptom relief, restore your gut health, and improve your quality of life.
Schedule a consultation today to get help in resolving your SIBO.