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Lactose intolerance

Also known as: Lactase persistence, lactose tolerance

Test category:

Familial - Gastrointestinal; Immunology- Gastrointestinal; Paediatric- Gastrointestinal

Use of test


The ‘lactose intolerance genetic test’, also referred to as the ‘lactase persistence’ test, differentiates between primary lactose intolerance due to lactase deficiency, and secondary causes of lactose intolerance due to other more serious conditions that affect the small bowel.

Lactose is the major carbohydrate in mammalian milk.  Lactose intolerance is caused by a deficiency of lactase, the enzyme required for digestion of lactose

After infancy, approximately 70-75% of the population lose the ability to digest lactose due to a deficiency in lactase, referred to as primary lactose intolerance. The remainder of people maintain their tolerance for lactose-containing foods because of genetic variants that enable continued production of lactase, referred to as lactase persistence.


This test detects the genetic variant c.-13910C>T that accounts for close to 100% of lactase persistence in Europeans.  Three other genetic variants that have a similar effect and are more common in non-European populations are also detected.  These variants are thought to act as enhancers of the LCT gene (encoding the lactase enzyme) that in turn stimulate lactase production.  When one of these variants is found, a diagnosis of primary lactose intolerance can be excluded.

Lactose intolerance can be secondary to other conditions that affect the small bowel, such as gastroenteritis, inflammatory bowel disease and coeliac disease. This test can help to distinguish between secondary causes and lactose intolerance due to a deficiency of lactase.

Ethical considerations:

This is an assay for heritable variants which can alter the probability that a person will develop a disorder.

Requesting the test


This test can be requested by any medical practitioner.

Sample required:

2-4 mL blood in EDTA (room temperature) or buccal swab (Copan flocked swab (red) or Sigma transwab (orange)).

Specimens may be collected by the requesting practitioner or at any Sonic Healthcare collection centre (see link below). Note: Not all collection centres hold buccal swab collection kits. Please contact them first if this is the preferred sample.

To help ensure the quality of the test, a genetic test should be done with a dedicated sample whenever possible i.e. a sample collected specifically for that test rather than a sample that is used for multiple tests.

We also recommend that the patient or another adult check the labelling of request forms and sample tubes.

>Link to Sonic Healthcare collection centres

Turnaround time:

5 business days from receipt of sample in the laboratory.



The laboratory assumes that the requestor has obtained financial consent from the patient for this test.


There is no Medicare rebate for this test. 

Click here for our billing policy.