Carbohydrate breath test for lactose or fructose intolerance

Carbohydrate breath test for lactose or fructose intolerance

What is a carbohydrate breath test?

These simple carbohydrate intolerance breath tests can provide information on whether you have an intolerance to sugars such as lactose or fructose.

You may be referred for a test if you are experiencing symptoms including diarrhoea, nausea, bloating, gas and abdominal cramps as many of these symptoms can be attributed to digesting foods with certain sugars and carbohydrates. A lactose intolerance breath test can help to uncover malabsorption of lactose (the sugar in dairy), and a fructose intolerance test can identify malabsorption of fructose (fruit sugar).

SIBO (Small Intestinal Bacterial Overgrowth) can cause a false positive result on these tests, so we always recommend to rule out SIBO with a SIBO breath test before taking an intolerance test.

Types of kit available


How does a carbohydrate breath test work?

you will provide an initial breath sample by blowing into a test tube through a straw, or into a breath collection bag. This will give us your baseline reading.

Then, you will drink water containing a carbohydrate (fructose or lactose) which needs to be drunk over a minute or two.

Breath samples then need to be taken every 40 minutes for three hours and 20 minutes, to monitor how your body is processing the carbohydrate. Along with the samples, you will record any symptoms experienced using the symptom form provided in order for your clinician to have a comprehensive overview of data and symptoms to analyse.

How much does a carbohydrate breath test cost?

If you are paying for this test yourself and not through private medical insurance, the cost will be £250 for a postal test.

How do you prepare for a carbohydrate breath test?

There is some preparation required before your test. This preparation involves stopping certain medication and fasting. Please see our lactose and fructose malabsorption leaflets for full details.

What does a carbohydrate breath test show?

People who are intolerant to lactose have very little or not enough of the enzyme lactase, which means that lactose cannot be broken down as normal in the small intestine. This means any lactose ingested passes through the large intestine where it is broken down by bacteria, producing large amounts of gases such as hydrogen and methane.

Fructose intolerance can be caused by a lack of fructose carriers in the cells of the small intestinal wall. This causes an increased amount of fructose in the small intestine which cannot be absorbed. It then passes to the large intestine where it is broken down by bacteria, also producing gases such as hydrogen and methane.

In both cases, these gases are absorbed into the bloodstream and transported to the lungs. They are then exhaled via the lungs and can be collected in breath samples for analysis. They can both be detected by a carbohydrate breath test.

Following your test, your data will be analysed and results written up into a report. The report will be sent to both you and your referring consultant/doctor, who will explain the results to you in a follow-up consultation and find the next step for managing your symptoms.

Information leaflets
Information leaflets

Find more information about these tests using our PDF downloads.

Lactose Malabsorption Fructose Malabsorption
Breath test information

Breath test information

This test can be done at home.

An excellent service from beginning to end. I would recommend to anyone who was considering having testing done. Very friendly and knowledgeable

Manchester Patient