Breath testing

A complete solution for the diagnosis of small intestinal bacterial overgrowth (SIBO) or carbohydrate malabsorption.

Our test is a simple patient-friendly, non-invasive, cost-effective hydrogen and methane breath test to detect SIBO or carbohydrate malabsorption.

Your patients can do the test in the convenience of their own home at a time that suits them or in an out-patient setting if that is preferred.

What is included in the kit?

The kit contains everything needed to enable your patient to do the test:

  • Test tubes
  • Straw
  • Substrate (test dependent)
  • Labels
  • Symptom sheet
  • Instruction leaflet
  • Freepost envelope to post back for analysis

How do patients do the test?

Patients need to follow a restrictive diet (‘the white diet’) the day before their test followed by a 12-hour fast. On the day of the test, they drink a substrate solution which is a mixture of water and carbohydrate (lactulose, glucose, lactose or fructose depending on which test they are doing), after which they will collect breath samples over a period of 2 – 4 hours (test dependent) by simply breathing into a test tube using a straw. They also complete a symptom sheet rating any bloating, nausea or abdominal pain they experience during the test.

Once the test is complete, the kit is returned in the freepost envelope to Functional Gut Diagnostics Ltd for analysis of hydrogen and methane using state of the art gas chromatography.

Results are reported within 5 working days of receipt of the completed kit at our laboratory.

Click here to see a sample report which includes results, conclusion and graphical representation of the results and patients’ symptoms.

Types of kit available


  • SIBO (lactulose)
  • SIBO (glucose)
  • Lactose
  • Fructose

Our kits are compliant with the requirements of the Hydrogen and Methane-based Breath Testing in Gastrointestinal Disorders: The UK Consensus – Association of GI Physiologists and the British Society of Gastroenterology.

Interested in using these kits in your private or NHS practice, call now on 0161 302 7777 to find out more.


SIBO hydrogen and methane breath test instructional video

Can I buy kits for use in my private practice?

Yes.  You can buy kits from us for use in your private practice, all we need is to set you up on our system and for you to provide us with a PO number.

Can the kits be used by the NHS?

Yes. There are several NHS hospitals already using the kits as they have significant benefits for both patients and the hospital:

  • Patient-centric option as the test can be done at home or in an out-patient setting if preferred
  • No capital outlay or ongoing maintenance costs
  • Reduction in waiting lists
  • Reduction in staff burden
  • Cost of the kit is well within the current NHS tariff


Is there any preparation my patients need to do before the test?

Yes.  Your patients will need to stop certain medication, follow a restricted diet and fast.  See all the details below:

  • For four weeks before the test, patients need to stop taking antibiotics
  • For one week before the test, patients need to stop taking any laxatives or stool softeners, stool bulking agents and probiotics.
  • The day before the test, patients need to follow the ‘white food’ diet as described in the kit instructions.
  • Patients must fast for 12 hours before the test.
  • On the day of the test, patients should not eat or drink anything, they can have small sips of water (300 ml) until the start of the test.  Essential medication can be taken with water but nothing that would affect the bowel.

What is the difference between glucose and lactulose substrates for testing for SIBO?

Glucose is absorbed by the digestive tract so it will not be able to detect SIBO that is further along in the small intestine (proximal jejunum/ileum).  If patients have had any bariatric or intestinal/bowel surgery, we would recommend using glucose as transit times may be quicker.

Lactulose is not absorbed by the digestive tract and will therefore travel through the entire gastrointestinal track, providing a complete picture for all intestinal segments.

How long are breath samples stable for?

The breath test samples are stable for up to two weeks across a wide temperature range  -20°C to 40°C.  Any samples received after two weeks of collection will be invalid.

What reporting criteria do you use for SIBO?

There are two main consensus documents that people follow when interpreting SIBO breath test results, the North American Consensus 2017 and the European Guidelines published by Ledochowski.

European SIBO cut off values ≥ 10 ppm rise in hydrogen above baseline within 60 minutes

North American SIBO cut off values ≥ 20 ppm rise in hydrogen above baseline within 90 minutes

We provide a report using both the above as consultants have their own preferences as to which parameters they prefer to use.

Most patients come out either positive for both parameters or negative for both parameters, but in instances where the results are conflicting, we will look at patient symptoms during the test to inform the borderline result or recommend a follow-up glucose test to provide clarity.