Hydrogen / methane breath test for bacterial overgrowth – Testing at home

Small intestinal bacterial overgrowth (SIBO) occurs when excess bacteria grow in the small intestine. This is where glucose is usually absorbed.

Under normal circumstances the amount of hydrogen and methane in your breath will remain unaltered as the glucose drink we give you is absorbed in the small bowel. If SIBO is present, the glucose will be digested by the bacteria and produce gases which are released in your breath.

SIBO is most common in patients with illnesses which directly or indirectly affect the movement or structure of the gut and causes symptoms such as diarrhoea. It is uncommon in patients with no underlying illness. The initial treatment for SIBO is a course of antibiotics. Most patients remain symptom free. However, some people require a repeat dose of antibiotics.

There are no risks involved with having a breath test. If you are diabetic, please see 'How do I prepare for my breath test?' below.

There are no alternative tests to investigate SIBO at UCLH. If you decide not to do this test, we will let your referrer know who will then discuss follow-up options with you.

Medications:

• Do not take probiotics for 4 weeks before the test. Probiotic foods such as yogurt or fermented foods are not included and can be eaten.
• Do not take antibiotics for 4 weeks before the test. If you are on a short course then please continue the medication and complete the test 4 weeks after finishing. If you routinely take daily antibiotics, you do not need to stop them before doing the test.
• Do not take laxatives for 1 week before the test (if you only take them occasionally). If you routinely take daily laxatives, continue to take these and stop 24 hours before the test.
• Do not take medications that affect your gut motility for 24 hours before the test (e.g. metoclopramide, prucalopride, baclofen).

The day before and day of your test:

• Please avoid high fibre foods e.g. beans, pulses, lentils, vegetables such as broccoli and cauliflower, and wholemeal products.
• Please do not have anything to eat or drink (except for water) for 13 hours before your test. Please do not chew gum. We suggest you complete your breath test in the morning, so this usually means fasting overnight and missing breakfast.
• Please do not smoke for two hours before your test.
• Brush your teeth as normal but do not use mouthwashes which contain alcohol.

During the test:

• Do not eat or drink anything. Do not smoke. Do not exercise or increase your activity.

NB: If you are diabetic, please consider the fact that you will be drinking the equivalent of a medium or small sized carbohydrate meal (75g of glucose). If you are insulin dependent, you may need to alter your dose accordingly.

Please contact us if you have any problems or queries.

Each sample bag should have a white clip on one end and a blue stopper on the other. If you have been given a bag of white clips and a bag of blue stoppers, please place a clip on one end and a blue stopper on the other, for each sample bag. Each bag should look like this:

• All samples should be taken in a resting, seated position. Take a deep breath in and hold for as long as you can, up to 15 seconds.
• Gently breathe out into the open air until you have exhaled approximately 50-75% of your breath. This is because we only want the end part of your breath in the bag.
• Place your lips around the tube which has the white clip on and exhale the end of your breath into the bag.
• Once you have exhaled completely into the bag, clip the white clip closed immediately to seal the gas in the bag. Do this before you remove the tube from your mouth.
• You can practice this as many times as you wish before you begin the test. You can use any bag to practice, just ensure you empty it again afterwards.

Put all the sample bags and your results sheet back into the box which they came in and close the box. Please return your box within one week of completing your test.

Please bring your box back to the GI Physiology Unit during our opening times and hand it in at reception. We are open 09:00-17:00, Monday to Friday.

If you wish to post your samples back to us, you will need to take your box to the Post Office and pay for return postage. Please use the return address label in your box, not the address on this page. Please send your box by normal post, not recorded delivery.

Sometimes you may need to do another breath test after the first one has been analysed, but before your result is finalised. If this is needed, we will tell you this when we telephone you after we have analysed the first test.

We will analyse your samples and put the test results into a report which will be sent to your referring doctor. A copy will also be saved onto the hospital system and sent to you and to your GP. When you return to see your doctor (for example at the outpatient clinic at the Trust, at another hospital, or your GP surgery) the test results and any treatment will be discussed with you.

You will be able to continue with your normal activities after the test. Please contact us if you have any problems.

This page tells you about hydrogen / methane breath tests but if you have read the page and have any queries, please contact the GI Physiology Unit.

Address: GI Physiology Unit, Lower Ground Floor, EGA Wing University College Hospital, 25 Grafton Way, London, WC1E 6DB

GI Physiology Administrator: 020 3447 9130 (Monday to Friday 09:00 to 17:00)

Switchboard: 020 3456 7890 / 08451 555 000, ext. 79130

Email: UCLH.GIphysiology@nhs.net

The GI Physiology Unit is on the lower ground floor of the EGA wing. You do not need to come to the hospital for your test.