Description
Important: This test cannot be combined with other tests in one transaction. Please order this test separately. Results in approximately 3 weeks.
Lactose intolerance is one of the most common metabolic conditions worldwide, yet it is frequently confused with irritable bowel syndrome, coeliac disease, or other functional gut conditions that produce near-identical symptoms. Our genetic test for lactose intolerance analyses the LCT gene polymorphism –13910C>T (rs4988235) in a blood sample sent to our accredited laboratory — giving you a clinically definitive answer based on your DNA, rather than a diet diary or breath test result that can vary day to day.
Unlike IgG or IgE allergy tests, this is a genetic (DNA) test — it identifies whether you carry the variant that determines lifelong lactase production. The result does not change over time and cannot be influenced by what you ate before the test.
What is lactose intolerance?
Lactose is the principal sugar found in milk and most dairy products. To be absorbed from the gut into the bloodstream, lactose must first be broken down into its two component sugars — glucose and galactose — by an enzyme called lactase, produced by cells lining the small intestine. When lactase is insufficient or absent, undigested lactose passes into the large intestine, where it is fermented by gut bacteria — producing gas, drawing water into the bowel, and triggering the characteristic symptoms of bloating, pain, flatulence, and diarrhoea.
Lactase activity is universally high during infancy, when milk is the sole source of nutrition. In most mammals — and in the majority of humans worldwide — lactase production declines genetically after weaning. This is called lactase non-persistence, and it is the biological norm. The ability to digest dairy into adulthood (lactase persistence) is, in evolutionary terms, the minority variant — one that developed in populations with a long history of dairy farming.
Approximately 75% of the world’s population loses the ability to fully digest lactose in adulthood. Prevalence varies dramatically by ethnicity:
| Population / Region | Estimated prevalence of lactose intolerance |
|---|---|
| North-western Europe (UK, Scandinavia) | Less than 5% |
| Central & Southern Europe | 15–40% |
| Middle East & Africa | 50–80% |
| South America & Sub-Saharan Africa | Over 50% |
| East & South-East Asia | Up to 100% |
In the UK, the condition is most prevalent in people of South Asian, East Asian, African, and Caribbean heritage, where lactase non-persistence rates are significantly higher than in the majority white European population. A genetic test provides an ancestry-independent, definitive result — particularly valuable for people of mixed or non-European heritage, where published prevalence estimates may be less predictive.
The science: the LCT gene and the –13910C>T polymorphism
The LCT gene on chromosome 2q21 encodes the lactase enzyme produced by intestinal cells. Whether the LCT gene remains active into adulthood is controlled by a nearby regulatory sequence within the MCM6 gene. A single nucleotide change in this regulatory region — the C>T variant at position –13910 (rs4988235) — is the key determinant of lactase persistence in European populations, and is associated with close to 100% of lactase persistence in Europeans.
Lactase non-persistence
Both chromosomes carry the original C variant. Lactase production declines after weaning. Primary lactose intolerance is likely in adulthood. This is the most common genotype worldwide.
Intermediate / partial persistence
One copy of each variant. Lactase activity is reduced but partial — some individuals can tolerate moderate amounts of lactose; others experience symptoms. Symptoms are often dose-dependent.
Full lactase persistence
Both chromosomes carry the T variant. Lactase production continues into adulthood. Primary lactose intolerance is unlikely — if symptoms are present, another cause should be explored.
Non-European variant detection: Our test also detects three additional variants more common in non-European populations: –13907C>G, –13913T>C, and –13915T>G (in MCM6 HGVS nomenclature: c.1917+329C>G, c.1917+323T>C, and c.1917+321T>G respectively). This makes the test clinically meaningful across all ethnicities, not just individuals of European descent.
Symptoms of lactose intolerance
Symptoms typically begin 30 minutes to 2 hours after consuming foods containing lactose. The onset and severity are directly related to the quantity of lactose consumed and the individual’s remaining lactase activity:
Bloating — distension and discomfort caused by gas produced by bacterial fermentation of undigested lactose in the colon
Abdominal pain or cramps — often described as griping or cramping, typically in the lower abdomen
Diarrhoea — loose, watery stools caused by osmotic water drawn into the bowel by unabsorbed lactose
Flatulence — excess gas from bacterial fermentation; may be the only symptom in mild cases
Nausea — often accompanies severe lactose malabsorption, particularly after large amounts of dairy
Delayed onset — symptoms typically appear 30 minutes to 2 hours post-ingestion, distinguishing them from immediate food allergy reactions
⚠️ Lactose intolerance vs. IBS and other conditions
Lactose intolerance shares its core symptoms — bloating, abdominal pain, diarrhoea, and flatulence — with irritable bowel syndrome (IBS), coeliac disease, small intestinal bacterial overgrowth (SIBO), and inflammatory bowel disease (IBD). Studies have found that up to 38% of IBS patients also have lactose malabsorption — meaning some patients carry both diagnoses simultaneously. A genetic test for the LCT variant is a crucial first step: a positive result confirms the genetic basis for lactase non-persistence, while a negative result (lactase persistence genotype) suggests the symptoms have another cause that warrants further investigation.
Primary vs. secondary lactose intolerance
🧬 Primary (genetic) lactose intolerance
Caused by the genetically programmed decline in lactase production after weaning. Identified by the –13910C>T LCT gene polymorphism. This is what this test detects. It is permanent and lifelong — dietary management (reducing or eliminating lactose) is the primary treatment.
📝 Secondary (acquired) lactose intolerance
Caused by damage to the lactase-producing cells of the small intestinal lining — from coeliac disease, Crohn’s disease, gastroenteritis, or SIBO. This can affect people who carry the lactase persistence genotype. If the underlying condition resolves, lactase activity may partially recover. A genetic test with a lactase persistence result (T/T or C/T) in someone with dairy symptoms should prompt investigation for secondary causes.
How the test works
This test uses a small blood sample (EDTA purple-top tube) posted to our accredited laboratory, where genotyping is performed by melt curve analysis using the TIB MOLBIOL Lactose Intolerance Lightmix IVD kit — a CE-marked, clinically validated diagnostic platform.
Order separately
This test must be ordered on its own — do not add other tests to the same transaction.
Receive your kit
Kit contains one purple-top (EDTA) tube, a laboratory request form, and a return envelope.
Label the tube
Write your date of birth and full name on the sample tube before collecting. Include the form when posting back.
Post & receive results
Post tube + form together. Results in approximately 3 weeks in your secure portal.
📋 Sample labelling is critical. Write your date of birth first, then your first and last name on the purple-top tube before collecting your sample. Unlabelled or incorrectly labelled samples cannot be processed by the laboratory.
Understanding your result
Your result will state whether the lactase persistence variants are detected or not detected, and provide an interpretation based on your genotype. Below is an example of a result indicating lactose intolerance:
Example positive result
Lactase persistence (LCT) genotyping
Specimen type: EDTA blood
Method: Melt curve genotyping
Result: No tested variants detected
Interpretation: Lactose intolerance possible (NOT EXCLUDED).
No genetic variants associated with being able to digest lactose beyond infancy (lactase persistence) were detected. When considered with other laboratory and clinical information, this result may be used to support a diagnosis of primary lactose intolerance.
Laboratory note: Genotyping is performed by melt curve analysis using the TIB MOLBIOL Lactose Intolerance Lightmix IVD kit. The test detects the –13910C>T variant (close to 100% of lactase persistence in Europeans) and also the –13907C>G, –13913T>C, and –13915T>G variants more common in non-European populations. In HGVS nomenclature these are described in reference to MCM6 gene (NM_005915.5) as c.1917+326C>T, c.1917+329C>G, c.1917+323T>C and c.1917+321T>G respectively. Secondary intolerance due to conditions affecting the small bowel should also be considered alongside genetic results.
Test details at a glance
- ✓Test type: Genetic (DNA) test — LCT gene polymorphism analysis
- ✓Variants detected: –13910C>T (primary), plus –13907C>G, –13913T>C, –13915T>G (non-European)
- ✓Method: Melt curve genotyping — TIB MOLBIOL Lightmix IVD kit
- ✓Sample: Finger-prick blood in purple-top (EDTA) tube
- ✓Collection: Remote (home) postal collection
- ✓Must be ordered on its own — cannot be combined with other tests
- ✓Turnaround: approximately 3 weeks from laboratory receipt
- ✓Results delivered to your secure patient portal
Frequently asked questions
How is a genetic test different from a hydrogen breath test for lactose intolerance?
A hydrogen breath test measures how much hydrogen your gut produces after ingesting a lactose load — it reflects current digestive function and can be affected by factors like gut bacteria composition, recent illness, or antibiotic use. A genetic test identifies whether you carry the variant that determines lifelong lactase production — the result is fixed and does not change over time. For primary lactose intolerance (the most common type), a genetic test is more definitive and requires no dietary preparation or special conditions on the day of testing.
Can I eat normally before the test?
Yes. Because this is a DNA test, what you eat or drink before the test has no effect on the result. No fasting, dietary changes, or preparation is required before providing your blood sample.
My result shows lactase persistence — why do I still get symptoms after dairy?
A lactase persistence genotype (C/T or T/T) means primary genetic lactose intolerance is unlikely. If you still experience symptoms after dairy, secondary lactose intolerance from an underlying gut condition — such as coeliac disease, Crohn’s disease, SIBO, or IBS — should be investigated by your GP. Additionally, some people have reactions to dairy proteins (casein or whey) rather than lactose itself, which requires separate investigation.
I’m of non-European heritage — is this test still relevant for me?
Yes. In addition to the –13910C>T variant (which accounts for close to 100% of lactase persistence in Europeans), our test also detects the –13907C>G, –13913T>C, and –13915T>G variants — which are more common in African and Middle Eastern populations. This makes the test meaningful across a wide range of ancestries, though it should be noted that some rarer variants specific to particular populations may not be detected.
What happens if my result is positive (lactose intolerance confirmed)?
A confirmed lactase non-persistence result supports a diagnosis of primary lactose intolerance. Management typically involves reducing or eliminating dietary lactose, using lactase enzyme supplements before consuming dairy, and choosing lactose-free dairy alternatives. Share your result with your GP or a registered dietitian, who can advise on ensuring adequate calcium and vitamin D intake alongside a low-lactose diet.
Why can this test not be combined with other tests?
The lactose intolerance genetic test uses a specific EDTA blood collection tube and dedicated laboratory logistics that require a separate transaction and return package. Adding other tests to the same order risks processing errors and sample rejection. Please complete a separate checkout for this test.
How do I access my results?
Results are delivered to your secure patient portal approximately 3 weeks after the laboratory receives your sample. Register before sending your sample at ukallergy.carebit.co/patients/accounts/sign-up.
This is a genetic (DNA) test for primary lactose intolerance analysing LCT gene polymorphisms (–13910C>T, –13907C>G, –13913T>C, –13915T>G) using melt curve genotyping. This test must be ordered separately and cannot be combined with other tests. Results are delivered to your secure patient portal approximately 3 weeks after laboratory receipt. This test is for informational purposes only and does not constitute medical advice or a clinical diagnosis. Secondary lactose intolerance due to underlying bowel conditions should also be considered. If you are experiencing severe or persistent gastrointestinal symptoms, please consult your GP.
Testing kit will consist of one purple top tube, please make sure to write date of birth first and last name on the sample tube and include the form before sending it back.