What Works Best in the UK?
Have you been diagnosed with Small Intestinal Bacterial Overgrowth (SIBO) and are unsure whether to use antibiotics or natural remedies?
In the UK, rifaximin is the most commonly prescribed antibiotic for SIBO but it’s not usually available on the NHS and can be expensive. Herbal antimicrobials, on the other hand, are widely available, often cheaper, and supported by clinical evidence.
This article reviews the effectiveness of rifaximin vs herbal therapy for SIBO, with a focus on UK availability, costs, and which option may work best depending on your breath test results.
What is SIBO
SIBO is a condition where bacteria that normally live in the large intestine build up in the small intestine. This can lead to bloating, abdominal pain, diarrhea, constipation, gas, and nutrient deficiencies.
One of the most widely prescribed treatments for SIBO is rifaximin, a non-systemic antibiotic that works locally in the gut. But how effective is it? And how does it compare to herbal therapy, let’s look at the evidence for Hydrogen and methane-dominant cases known as intestinal methanogen overgrowth (IMO). This article reviews the latest evidence.
What is Rifaximin and how does it work for SIBO?
Rifaximin is the most widely studied antibiotic for Small Intestinal Bacterial Overgrowth (SIBO). Because it acts locally in the gut and isn’t absorbed into the bloodstream, it has a good safety profile and is generally well tolerated. But like any treatment, it doesn’t work for everyone.
Clinical trials and meta-analyses show that rifaximin can clear SIBO in anywhere from 40% to 80% of cases. The wide range is due to differences in:
- The type of SIBO (hydrogen vs methane vs hydrogen sulfide)
- Rifaximin Dosage – The dose and duration used (standard courses are usually 550 mg three times daily for 10–14 days, but this may vary)
- Whether it’s used alone or in combination with other treatments
On average, about two out of three patients (≈65%) see significant improvementin both on their breath test results and their symptoms after a course of rifaximin.
Why Do Rifaximin Results Vary?
Not every patient responds to rifaximin in the same way. Several factors explain why results differ so widely:
Hydrogen-dominant SIBO
If your breath test shows excess hydrogen gas, you’re most likely to respond well to rifaximin on its own. Studies consistently show that people with hydrogen-dominant SIBO have the highest clearance rates, and you may notice rapid relief from bloating and diarrhoea.
Methane-dominant SIBO (also called IMO)
If your breath test results show high methane levels, it means methane-producing microbes are slowing down your gut motility.
This often causes constipation, gas, and bloating.
Treatment is usually more difficult and requires a combination of rifaximin and another antibiotic such as neomycin, or a herbal protocol including allicin (from garlic), oregano, or berberine.
Because methane organisms are stubborn, treatment may take longer and supporting your gut motility afterwards is especially important.
Two key studies indicate that rifaximin and neomycin may be best for methane-positive SIBO/IMO.
Low et al., 2010 (Cedars-Sinai) reviewed 74 patients and found that rifaximin + neomycin for 10 days (rifaximin 400 mg three times daily + neomycin 500 mg twice daily) outperformed either drug alone: 85% felt better on the combo (vs 63% on neomycin, 56% on rifaximin) and methane was cleared far more often (87% vs 33% and 28%, respectively).
Pimentel et al., 2014 then showed in methane-positive, constipation-predominant IBS that the combination again beat neomycin alone for overall symptom relief, with improvements tracking reductions in methane. Typically clinicians use rifaximin 550 mg three times daily + neomycin 500 mg twice daily for 14 days.
Hydrogen sulfide SIBO
If your breath test suggests high hydrogen sulfide, you may notice diarrhoea, abdominal pain, and a strong odour to your gas or stools. This type of SIBO can be trickier to detect, and treatments often include rifaximin with bismuth, or herbal antimicrobials such as oregano, berberine, and garlic.
Supporting your body’s sulfur metabolism and gut lining repair is also an important part of recovery.
All three types of SIBO (hydrogen, methane, or hydrogen sulfide) is usually identified with a breath test.
You can learn more about how this works on our SIBO Testing UK
Rifaximin Dose and Duration
- The standard regimen for rifaximin in SIBO is 550 mg three times daily for 14 days. That dose/duration is the one most frequently reflected in guideline tables and clinical studies. Note that trials have used a range of total daily doses (≈600–1,600 mg/day) and durations (5–28 days), which helps explain why reported success rates vary.
- Lower doses or shorter courses tend to have reduced success rates, as they may not fully suppress bacterial overgrowth. In general the better-studied regimens cluster around 10–14 days at higher total daily doses; very short courses (≤7 days) or low-dose schedules are less well supported and may be associated with lower eradication.
- Some patients require repeated courses, particularly if relapse occurs or if underlying causes have not been corrected. SIBO frequently recurs, so it’s common to repeat a course if symptoms and breath-test findings return, especially if underlying drivers haven’t been fixed (e.g., slow motility, long-term PPI use). Best outcomes come when you pair antibiotics with underlying causes.
Relapse After Rifaximin
Even after successful treatment, relapse is common. Studies show that 30 to 45 percent of patients relapse within 6 to 9 months. This is why treatment should always address underlying causes such as impaired motility, adhesions, or low stomach acid, and include strategies for long-term relapse prevention.
Why Isn’t Rifaximin Offered on the NHS for SIBO?
Rifaximin is rarely prescribed on the NHS for SIBO, and there are several reasons for this:
- Licensing: rifaximin is not licensed in the UK for SIBO, only for traveller’s diarrhoea, IBS-D, and hepatic encephalopathy.
- Evidence: although studies show up to 70 percent success rates, most trials are relatively small and use different protocols, making it harder for NICE to issue clear guidance.
- Cost: private prescriptions cost around £250–£400 for a 14-day course, and repeated courses are often required due to relapse. This makes rifaximin less cost-effective in NHS models.
- Guidelines: there is currently no NICE guideline pathway for SIBO, which means there is no formal NHS treatment protocol. Because of this, rifaximin is usually prescribed privately in the UK, through gastroenterologists or functional medicine clinics. For more information, see our page on SIBO Testing UK
Herbal Alternatives to Rifaximin for SIBO – How Does Rifaximin Compare to Herbal Therapy?
Yes! It many cases it can be superior
Many patients ask about natural alternatives to rifaximin. Research suggests that herbal antimicrobials can be just as effective in some cases.
A Johns Hopkins study compared rifaximin with herbal formulas containing berberine, oregano oil, and aromatic extracts. SIBO cleared in 46 percent of the herbal group and 34 percent of the rifaximin group.
Interestingly, 57 percent of patients who did not respond to rifaximin cleared SIBO after switching to herbs (Chedid et al., 2014). This suggests herbs can work for many, especially if rifaximin hasn’t helped.
Herbs prebiotics and Glutamine can halso help Intestinal Methane overgrowth
A 2024 randomised trial tested whether adding herbs, probiotics, prebiotics, and glutamine to rifaximin plus a low-FODMAP diet improved outcomes. Breath test clearance was similar in both groups, but methane-dominant patients reported greater symptom improvement when herbs and probiotics were added (Redondo Cuevas et al., 2024). Bottom line: adding herbs/probiotics/glutamine didn’t increase breath-test clearance beyond antibiotics + low-FODMAP overall, but it did improve symptoms in methane-dominant SIBO (≈78% vs 60%), so consider add-ons for methane-positive cases while ensuring adequate antibiotic dosing and fixing underlying drivers.
Berberine may be equivalent to Rifaximin
Another trial is currently neing run comparing berberine to rifaximin (Guo et al., 2023). Early studies suggest that berberine may achieve comparable clearance rates. The trial is directly comparing berberine (400 mg twice daily ×14 days) with rifaximin (400 mg twice daily ×14 days) for SIBO.
Early conference reports suggest berberine was not inferior to rifaximin but the full peer-reviewed results aren’t published yet.
Smaller studies have also shown that certain herbal blends can be helpful for gut health. For example, a combination of quebracho, conker tree (horse chestnut), and peppermint was tested in people with constipation-predominant IBS. The results were encouraging — participants experienced less bloating and found their constipation improved (Brown et al., 2016).
In a small 2024 study of breath-test–positive SIBO, a polyherbal protocol using Biocidin® (liquid), GI Detox®+ (binder), and the olive-leaf polyphenol formula Olivirex® was linked to improved gut symptoms and a measurable reduction in rosacea-type facial redness (Min, 2024). This highlights the close link between the gut and the skin, showing how restoring balance in the intestines can sometimes calm inflammation elsewhere in the body.
Together, these findings suggest that botanical formulas can be a powerful alternative or complement to antibiotics like rifaximin. They don’t just target overgrowth in the gut, but may also support wider health benefits.
Summary- common herbal antimicrobials used for SIBO include:
- Berberine
- Oregano oil
- Allicin (garlic extract)
- Neem
- Botanical blends (e.g., quebracho, conker tree, peppermint)
Why Herbal Therapy May Be the Better Option in the UK
If you’ve struggled with side-effects from antibiotics, had a relapse after rifaximin, or you’re methane-dominant (which often responds poorly to rifaximin alone), targeted botanicals can offer a practical, well-tolerated alternative often with extra benefits like anti-inflammatory, antifungal and gentle motility support.
Cost and access also matter: rifaximin can be hard to obtain on the NHS, so using herbs may be easier, faster, cost-effective and in some cases more effective than rifaximin.
Please see a summary of the main reasons you may wish to take herbs instead of rifaximin
- Rifaximin is very costly and typically not routinely prescribed on the NHS
- Herbs can be equally effective to rifaximin
- If you have methane-dominant SIBO, herbs may be a better option as this type of SIBO often responds poorly to rifaximin alone
- If you prefer a natural approach and cannot tolerate antibiotics or are concerned about side-effects.
- If you have relapsed after taking rifaximin, herbs may be effective in these cases and be a better option
- If you have other conditions such as Candida and want additional gut support. Many herbs also have anti-inflammatory, antifungal, or motility-supporting effects.
- If you are concerned about the risk of antibiotic resistance
Cost and Availability: Rifaximin vs Herbal Therapy
Rifaximin:
- Cost: £250–£400 for a 14-day course (private prescription).
- Availability: prescription only; not routinely available on the NHS for SIBO.
Herbal Therapy:
- Cost: £25–£80 depending on products used and duration (usually 4–6 weeks).
- Availability: widely available through practitioners and supplement suppliers; no prescription required.
Comparison Table
| Factor | Rifaximin (Antibiotic) | Herbal Therapy (Berberine, Oregano, Allicin etc.) |
|---|---|---|
| Effectiveness | ~40–70% clearance, higher in hydrogen SIBO | Can be equally effective as rifaximin |
| Best For | Hydrogen-dominant SIBO | Methane-dominant, mixed cases, rifaximin non-responders |
| Relapse | 30–45% within 6–9 months | Similar relapse rates, can be used longer term |
| Side Effects | Usually mild (nausea, diarrhoea) | Digestive upset possible, generally well tolerated |
| Resistance Risk | Some risk with repeated use | Very low due to multiple active compounds |
| Extra Benefits | Well studied, standardised dosing | Anti-inflammatory, motility support, antifungal |
| Cost (UK) | £250–£400 per 14-day course | £80–£150 per month (4–6 weeks) |
| Availability | Prescription only, private access | Practitioner-guided, widely available |
Key Takeaway
Both rifaximin and herbal therapy can be effective for SIBO, but the best choice depends on your breath test results, symptoms, and access to treatment.
- Hydrogen SIBO: Rifaximin is usually effective but expensive and herbal antibiotics may be equaly effective
- Methane or hydrogen sulfide SIBO: Herbal protocols often work better, or can be combined with antibiotics
- UK patients: Herbal therapy is more accessible, affordable, and often just as effective making it a strong alternative to private rifaximin prescriptions
If you’re struggling with SIBO symptoms and not sure whether rifaximin, herbal therapy, or a combined approach is right for you, consider booking private consultations to guide you through testing, personalised treatment plans, and long-term prevention strategies.
Book a SIBO Consultation. If you would like support with SIBO testing, personalised treatment plans, or guidance on herbal alternatives, see our SIBO testing page
FAQs
Is rifaximin available on the NHS for SIBO?
No. In the UK, rifaximin is not licensed for SIBO, only for IBS-D and traveller’s diarrhoea. It is generally prescribed privately.
How much does rifaximin cost in the UK?
A typical 14-day course costs £250–£400 privately, depending on the pharmacy.
Can herbal remedies work if rifaximin fails?
Yes. Studies show that over 50% of rifaximin non-responders clear SIBO with herbal therapy.
Which herbs are best for methane-dominant SIBO?
Allicin, oregano, berberine, and botanical blends are often used, sometimes alongside prokinetics to support motility.
References
- Chedid, V., Dhalla, S., Clarke, J. O., Roland, B. C., Dunbar, K. B., Koh, J., … & Pimentel, M. (2014). Herbal therapy is equivalent to rifaximin for the treatment of small intestinal bacterial overgrowth. Global Advances in Health and Medicine, 3(3), 16–24.
- Gatta, L., Scarpignato, C., Fiorini, G., et al. (2017). Systematic review with meta-analysis: rifaximin is effective and safe for the treatment of small intestine bacterial overgrowth. Alimentary Pharmacology & Therapeutics, 45(5), 604–616.
- Guo, J., Sun, Y., Zhang, H., et al. (2023). Berberine versus rifaximin for patients with small intestinal bacterial overgrowth: a randomized controlled trial. Frontiers in Microbiology, 14, 1185432.
- Redondo-Cuevas, L., Hernando, M., et al. (2024). Effect of adding herbal antimicrobials, probiotics, and dietary therapy to rifaximin for small intestinal bacterial overgrowth: a randomized clinical trial. Nutrients, 16(2), 311.
- Brown, K., Gerbarg, P. L., Muskin, P. R., & Mishra, L. (2016). Randomized, double-blind trial of a botanical blend (quebracho, horse chestnut, peppermint) for constipation-predominant IBS. Journal of Alternative and Complementary Medicine, 22(12), 964–972.
- Min, Y. W., et al. (2024). Effects of a polyherbal formula on small intestinal bacterial overgrowth and associated rosacea: an open-label study. Integrative Medicine Research, 13(1), 100918.
- Pimentel, M., et al. (2006). Rifaximin therapy for patients with irritable bowel syndrome without constipation. New England Journal of Medicine, 364(1), 22–32.
About the Author
Victoria Tyler a UK registered Nutritional Therapist and member of the British Association of Nutritional therapy. She was awarded UK BSc Honours Degree in Nutritional Therapy and has trained in GI Functional Medicine. Victoria has been working with Gut disorders since 2004 after first experiencing digestive problems herself. She felt that the NHS was unable to provide the support individuals needed and went on to specialise in this area before offering a bespoke IBS service.
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