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Clinical Engineering

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Hydrogen breath test


Hydrogen Breath Test

The Hydrogen Breath Test (HBT) is a simple test to investigate the gastro-intestinal tract for, Bacterial overgrowth. (GLUCOSE), and Lactose malabsorbtion. (LACTOSE).

These abnormalities can cause diarrhoea and other related problems.

The test involves the fasted patient swallowing a solution of glucose or lactose after which the end-expired breath hydrogen level is monitored. An increase in breath hydrogen indicates bacterial action on the administered carbohydrate which can be due to one or both of the above abnormalities. The test can take up to 2 hours.


The tests are only done on referral from a medical or surgical consultant employed by the Royal United Hospital NHS Trust.

Outpatients (including private patients)

Requests for a HBT are made on a request form or by letter from the consultant, directly to Medical Physics. Patients are admitted to the Clinical Imaging and Measurement Department (C16) at 9:00am. Note that tests are done in the morning for the sake of the patient's comfort since they are required to fast overnight.


Requests for tests on an in-patient may be by form or phone, and confirmed in writing. The test is usually done at the bedside. A date is established in liaison with the nursing or medical staff who should be aware of any other tests. In general, the HBT is not carried out on the same day as a clinical imaging scan, X-ray procedure or endoscopy examination.


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