Lactase gene (LCT, lactose intolerance genetic test)

The test looks at a genetic variant upstream of the lactase gene (LCT, variant −13910 C/T) that determines whether the enzyme lactase stays active in adulthood. The sample is EDTA blood; as a genetic test, written consent is required.

What lactase does in the body

Lactase sits on the surface of small-intestinal cells and splits milk sugar (lactose) into glucose and galactose, which are then absorbed. In most people worldwide, lactase declines after early childhood; the T variant keeps it active.

Genotype CC – what happens in the body?

With genotype CC, lactase activity declines over the course of life. Unsplit milk sugar then reaches the colon, binds water and is fermented by bacteria: hydrogen, carbon dioxide, methane and short-chain fatty acids are produced. Bloating, abdominal cramps and diarrhoea after dairy products can result – how strongly depends on the remaining lactase and the amount.

Genotype CT or TT – what does it mean?

With at least one T variant, lactase usually stays active for life. Temporary lactose intolerance due to a damaged small-intestinal lining, for example after infections or in coeliac disease, is not detected by the genetic test – the lactose breath test is suitable for that.

The interpretation is given in your report.