Lactose Intolerance Test

Testing for lactose intolerance

If you’ve noticed yourself feeling ‘off’ after eating dairy, it may be because you’re intolerant to lactose. In today’s article, we’re going to look at how you can test for lactose intolerance and more inportantly how to do a lactose intolerance test at home. But first, let’s look at what lactose is and what symptoms you might experience if you’re lactose intolerant.

What is lactose?

Lactose is a sugar found in all dairy and dairy products.


Lactose intolerance occurs when you don’t digest lactose properly. This happens when you don’t have enough enzyme lactase to break down and absorb the lactose.


Lactose is one of the FODMAP sugars that have identified and extensively researched by Monash University. FODMAPs are sugars that are poorly absorbed and can cause symptoms of irritable bowel syndrome (IBS). Monash University found that avoiding these sugars could help improve symptoms in three out of four people with IBS.

What are the symptoms of lactose intolerance?

If you are intolerant to lactose, you may experience symptoms like:

  • bloating
  • burping
  • excessive gas
  • abdominal discomfort or cramping
  • nausea (and sometimes vomiting)
  • constipation
  • diarrhoea
  • a sudden urge to move your bowels within 30 minutes to 2 hours after eating dairy

Lactose intolerance mainly affects the digestive system, though other non-digestive symptoms may include:

  • headaches
  • poor concentration
  • tiredness
  • muscle or joint pain
  • issues with urinating (like frequent urination or bedwetting)
  • skin conditions (like eczema)

The types of symptoms you get and how severe they are depend on how much lactase enzyme your body produces and how much dairy you eat. The symptoms are different for each person and range from mild to significant discomfort.

How do you test for lactose intolerance?

There are several ways to test for lactose intolerance. Some of these are more time-consuming and labour-intensive than others. Let’s look at each of them and how they might be beneficial.

  • Food challenge test

    A food challenge is the most basic way to determine if you have a food intolerance. It must be done under the supervision of a practitioner as it involves eliminating all sources of dairy from your diet. Having the guidance of a practitioner is essential to avoid nutrient deficiencies and for advice on how to do the elimination diet correctly and for how long.

    The elimination diet is usually maintained for four or more weeks. During this time, you will be instructed to record any changes in your symptoms. Your practitioner will then guide you with reintroducing the dairy, a process known as an ‘oral food challenge’. Again, it’s important to note any changes in your symptoms after reintroducing the dairy back into your diet.

    The food challenge can tell you whether you may be reacting to dairy. However, it can not specifically tell you whether you are lactose intolerant. It is a general test to check whether or not the consumption of dairy is contributing to your symptoms.

  • Breath test

    The breath test is a simple and definitive test for lactose intolerance. The test works by measuring the amount of hydrogen in your breath after you drink a solution of lactose. The more hydrogen you breathe out, the more intolerant you are to lactose. 


    To do the test, you will need to prepare by avoiding certain foods and medications and fasting overnight. You will then take a ‘baseline test that measures the hydrogen in your breath before introducing the lactose. To do this, you breathe into a balloon-like device that captures your breath in a vial.

    After drinking lactose mixed in water, you then repeat the breath test every 15-minutes for two to three hours. Regular intervals needed to measure how much the hydrogen increases in your breath over time and exactly how the lactose is affecting your gut.

  • Blood sugar test

The blood sugar test also involves drinking a large amount of lactose mixed in water. The test then measures how much glucose is in your bloodstream. If you are lactose intolerant, the glucose will rise very slowly or not at all. This is because you are not absorbing lactose properly. Lactose breaks down into glucose before entering your bloodstream, so not absorbing the lactose will mean that the glucose doesn’t show up as much in your blood.

  • Genetic test

    The genetic test is another type of blood test. It looks at whether you have the genes needed to produce the enzyme lactase. 


    Some people are lactose intolerant because their genes don’t allow them to produce much lactase after childhood. This is known as ‘primary lactose intolerance. In this case, genetic testing is helpful. It will also tell you if you will be lactose intolerant for life. 

    Lactose intolerance can also occur because of other digestive issues that irritate the gut lining and reduce the lactase enzyme. This includes food poisoning, having other food intolerances, or having coeliac disease. This is known as ‘secondary lactose intolerance’ and is not picked up with the genetic test. Because of this, the genetic test is used in combination with other lactose intolerance tests to make sure that lactose intolerance isn’t missed.

  • Stool acidity test

The stool acidity test is used mainly for infants and young children because the other tests, like the breath test, are too difficult or inappropriate for little ones. To do the test, a practitioner will give the child a lactose drink and collect the stool sample. Usually, the stool is not acidic, but if lactose isn’t broken down properly, then acids (like lactic acid) will show up in the stool. The more acidic the stool, the more lactose intolerance is an issue.

  • Hair test

Like the one we offer at Intolerance Lab, the hair intolerance test is a quick and non-invasive way to check for food intolerances. It can also be done at any age and you can do this lactose intolerance test at home. To do the test, simply order it online HERE, and post a sample of your hair to our lab. The test looks at over 350 foods and 350 non-food items that you may be reacting to. Results that are rated at 85% or more are positive – which means that they are the foods or items that you are most likely reacting to. Once our lab receives your sample, you can expect your results to be emailed to you within three days.



Today we looked at what lactose intolerance is and the symptoms you might experience if you are lactose intolerant. We then explored the different ways that you can test for lactose intolerance. We looked at the uses and benefits of some of these tests, as well as how they are conducted. One of the tests we discussed is our simple hair intolerance test that you can do from home and receive the results of over 700 intolerance triggers within three days. To order the test, simply click HERE and do a lactose intolerance test at home.


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