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SIBO breath test - private in London.

A 2 to 3 hour lactulose or glucose breath test measuring hydrogen and methane, with consultant gastroenterology review and a proper treatment plan if positive.

A friendly doctor in conversation with a patient in a warmly lit consulting room

Indicative pricing

What a private SIBO breath test costs in London.

Indicative ranges across UK private providers and laboratories.

In short

£180–£350 all-inclusive, with results back in 3 to 5 days.

Test or bundle Indicative range
Lactulose hydrogen breath test £180–£280
Glucose hydrogen breath test £180–£280
Hydrogen and methane combined (SIBO/IMO) £220–£350
Trio-smart (H2, CH4, H2S) £280–£420
SIBO test + gastro review £380–£650
Full IBS work-up bundle £550–£950

Prices vary by substrate, whether methane is measured alongside hydrogen, whether a consultant review is bundled in, and how quickly you need the report.

What SIBO is

Too many bacteria, in the wrong part of the gut.

Small intestinal bacterial overgrowth (SIBO) is exactly what it sounds like - excess bacteria colonising the small bowel, where the numbers are meant to be low. The result is fermentation where it does not belong: bloating within an hour of eating, gas, altered bowel habit and, over time, malabsorption of iron, B12 and fat-soluble vitamins. When the overgrowth is dominated by methane-producing archaea, the pattern shifts to intestinal methanogen overgrowth (IMO) and constipation. A breath test is how the two are told apart.

Who benefits from testing

When a SIBO breath test is the right call.

SIBO hides behind a lot of “IBS that will not shift”. These are the clinical patterns that most often turn out to be overgrowth in disguise.

  • Bloating unresponsive to IBS treatment

    Chronic bloating that has not settled on antispasmodics, low-FODMAP or a peppermint trial deserves a proper look for SIBO.

  • Post-cholecystectomy diarrhoea

    Loose, urgent stools after gallbladder surgery can reflect bile-salt malabsorption - or bacterial overgrowth downstream.

  • Abdominal surgery or adhesions

    Blind loops, resections and adhesive obstruction disrupt small-bowel motility and set the stage for overgrowth.

  • Motility disorders

    Gastroparesis, chronic intestinal pseudo-obstruction and diabetic autonomic neuropathy are classic SIBO backdrops.

  • Scleroderma and connective tissue disease

    Systemic sclerosis and related conditions slow small-bowel transit - overgrowth is common and treatable.

  • Long-term PPI use

    Sustained acid suppression removes the stomach’s antibacterial barrier and is a recognised SIBO risk factor.

  • Unexplained iron or B12 deficiency

    Overgrowth can cause fat, iron and B12 malabsorption - worth testing when the usual work-up is blank.

  • Red flag symptoms

    Weight loss, blood in the stool, nocturnal diarrhoea or a family history of bowel cancer need endoscopy or colonoscopy - not a breath test.

Available tests

Substrates and gases - what each option measures.

Lactulose is more sensitive, glucose is more specific for proximal SIBO, and adding methane (and, on newer panels, hydrogen sulphide) changes what you can actually treat.

  • Lactulose hydrogen breath test

    More sensitive but less specific. Lactulose is not absorbed, so it travels the length of the small bowel - useful for distal overgrowth.

  • Glucose hydrogen breath test

    More specific but only samples the proximal small bowel, because glucose is absorbed within 60 to 90 cm. The right choice for proximal SIBO.

  • Hydrogen and methane combined

    Adds methane to catch intestinal methanogen overgrowth (IMO) - the archaea-driven pattern behind constipation-predominant symptoms.

  • Trio-smart (H2, CH4, H2S)

    Newer three-gas test that also measures hydrogen sulphide - the pattern linked to diarrhoea-predominant symptoms and sulphurous wind.

  • + Gastro review

    Breath test bundled with a consultant gastroenterologist review, same visit, so a positive tracing becomes a treatment plan on the day.

  • Faecal calprotectin

    A stool marker to rule inflammatory bowel disease in or out before or alongside the breath test.

  • Endoscopy with duodenal aspirate

    The reference standard for proximal SIBO - reserved for diagnostic uncertainty or treatment failure.

  • Anorectal manometry

    Where constipation dominates and biofeedback may be needed alongside methane-targeted treatment.

Preparation and practicalities

Simple to do - if you follow a few rules.

The breath test is non-invasive and safe, but preparation is everything - antibiotics, probiotics, diet and even a morning run can all change the tracing. Follow the written instructions from the testing provider exactly.

  • Stop antibiotics four weeks before

    Any antibiotic course in the previous four weeks can suppress the overgrowth and cause a false negative. Allow four full weeks after the last dose.

  • Stop probiotics two weeks before

    Probiotic supplements and live-culture yoghurts alter the fermentation pattern - stop for at least two weeks before the test.

  • Hold prokinetics one week before

    Erythromycin, prucalopride and similar motility agents change small-bowel transit time and can distort the tracing.

  • Low-fermentable diet 24 to 48 hours before

    Plain chicken, fish, eggs, white rice, potato and clear broth. No fibre, legumes, dairy, onions, garlic or sweeteners the day before.

  • Fast twelve hours before

    No food or drink other than plain water for twelve hours before the appointment. No smoking or vaping either - both change breath gases.

  • No exercise on the morning

    Vigorous exercise on the day of the test can hyperventilate off hydrogen. Take it easy and travel gently.

  • PPIs are usually fine

    Unlike the H. pylori breath test, PPIs do not need to be stopped for a SIBO breath test. Chronic PPI use is often the reason for testing.

  • Retest timing after treatment

    Repeat testing to confirm response is done four to six weeks after antibiotics - sooner is unreliable, later loses the treatment signal.

Reading your report

The breath-test tracing looks intimidating. It isn't.

Whichever laboratory runs the samples, the report follows the same four parts. And a positive SIBO breath test needs a real treatment plan, not just a label - targeted rifaximin (plus neomycin or metronidazole where methane is high), a sequenced low-FODMAP or bi-phasic diet, a prokinetic where motility is the driver, and honest work on the underlying cause.

A UK consultant gastroenterologist reviewing a SIBO breath test tracing

A quiet reminder

Read the impression first - the tracing is the working.

If anything in the report is unclear, ask your gastroenterologist or GP to talk you through it.

  1. 01 Header

    Your details, indication and medications

    Your details, the clinical question, and every medication that could influence the result - antibiotics, probiotics, prokinetics.

  2. 02 Technique

    Substrate, timing and gases measured

    Which substrate was used (lactulose or glucose), the sampling schedule, and whether hydrogen alone or hydrogen and methane were measured.

  3. 03 Findings

    The breath tracing and cut-offs

    A rise in hydrogen greater than 20 ppm above baseline within 90 minutes, or methane at or above 10 ppm at any point, meets the North American Consensus criteria for a positive test.

  4. 04 Impression

    The conclusion: read this first

    Positive or negative - hydrogen-predominant SIBO, methane-predominant IMO, mixed, or normal - and the treatment implications. Read this first.

Recognised by major UK insurers

BupaAXA HealthVitalityAvivaWPACignaHealixBupaAXA HealthVitalityAvivaWPACignaHealixBupaAXA HealthVitalityAvivaWPACignaHealix

Cover varies by policy.

Frequently asked

Common questions about SIBO breath testing.

Quick answers on fasting, antibiotics, probiotics, diet, insurance and how often to repeat the test.

  • Do I need to fast before a SIBO breath test?

    Yes. You need to fast for twelve hours before the appointment - plain water only. On top of that, you are usually asked to eat a low-fermentable diet for the 24 to 48 hours before: plain chicken, fish, eggs, white rice, potato and clear broth. No fibre, legumes, dairy, onions, garlic or artificial sweeteners the day before. The testing provider will give you full instructions.

  • How long do I have to stop antibiotics before the test?

    Four full weeks after your last antibiotic dose. Anything sooner and the tracing is likely to give a false negative because the overgrowth is still suppressed.

  • Do I need to hold my probiotics or supplements?

    Yes. Stop probiotic capsules and live-culture yoghurts for at least two weeks before the test - they change the fermentation pattern in ways that muddy the tracing. Motility agents such as erythromycin or prucalopride should be paused for one week. Most other medicines are fine, but check with the testing provider or your GP first.

  • Lactulose or glucose - which one should I have?

    Lactulose is more sensitive because it travels the whole length of the small bowel, so it picks up distal overgrowth. Glucose is more specific but only samples the proximal 60 to 90 cm. In practice, lactulose is often used for bloating and diarrhoea-predominant symptoms and glucose when the picture points at proximal SIBO. Some laboratories run both.

  • Will my private medical insurance cover a SIBO breath test?

    Sometimes. Bupa, AXA Health and Vitality will often authorise the test when it is requested by a consultant gastroenterologist as part of a workup for bloating, malabsorption or persistent IBS symptoms. Cover for self-referred testing is patchy.

  • How often should the test be repeated?

    A repeat test to confirm response is done four to six weeks after finishing antibiotics. Beyond that, testing is symptom-led rather than routine - if symptoms recur or a new trigger appears (surgery, a course of antibiotics for something else, a slow-transit flare) it is reasonable to retest, but repeating it every few months in a stable patient is not usual.

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