Lactose Tolerance Test

A lactose tolerance test or LTT is used to diagnose intolerance symptoms in Irritable Bowel Syndrome through use of a simple hydrogen breath test or blood sample.

So you want to do a analysis to see if you have the condition, but how do you go about this and is there anything difficult in making the diagnosis?

You know that you have the intolerance symptoms including wind, bloating, diarrhea, nausea and tummy pain, but they can be common to a lot of bowel conditions so you want to be sure.

Lactose Tolerance Test

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  • HBT - the hydrogen breath test

How To Perform A Lactose Tolerance Test

Well, there are two main ways that you can do. The first is a blood sample, the second a hydrogen breath test:

Blood Sample

This is easy to do. First of all you need to starve yourself for 8 to 12 hours (including drinks).

You then need to take a sample of blood to measure your blood sugar level. Once this has been done, you will need to have a drink that contains the milk carbohydrate followed by a further blood sample.

If it is normal, you would expect a rise in the blood sugar level as the lactase enzyme will break down milk carbohydrate in to glucose and galactose which will then be absorbed in the small bowel.

If you are intolerant you won’t expect to see a sugar rise in the blood sugar as the lack of lactase enzyme will prevent this from happening.

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Hydrogen Breath Test

The HBT is a simple way of determining whether you have difficulty with handling lactose in the small bowel.

Normally when you swallow foods containing the sugar, the small bowel absorbs the break down products. If this isn’t achieved, bacteria in the small bowel ferment the milk carbohydrate creating hydrogen.

In an HBT, you will fast for 8 to 12 hours. A baseline breath sample is then taken for measurement. You will then be given lactose and a further breath sample taken.

If you have intolerance, the hydrogen levels go up and these will be absorbed in the bowel. You will then breath this out so increased levels of hydrogen will indicate a positive result.

The only problem with this lactose tolerance test is that it is not specific though!

If you have small intestinal bacterial overgrowth (where there are excessive numbers of bacteria in the small bowel) the result is likely to be positive too so a positive result needs to be treated with caution.

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