Coeliac Disease Test: Blood Tests, Home Tests and HLA Genetic Testing Explained
- Aug 11
- 12 min read
Digestive problems, persistent tiredness, unexplained nutritional deficiencies or a family history of coeliac disease can all lead someone to look for a coeliac disease test online.
Several options are available in the UK. These include laboratory blood tests, home finger-prick tests that detect antibodies, and genetic tests looking for HLA-DQ2 and HLA-DQ8.
However, these tests do not answer the same question.
An antibody test looks for evidence of an immune response associated with active coeliac disease while you are eating gluten. A genetic test asks something different: whether you carry the HLA variants that make coeliac disease genetically possible.
This distinction matters. An HLA genetic test can be particularly useful for ruling coeliac disease out in selected situations, but a positive genetic result cannot confirm that you currently have the condition.
Understanding what each test can and cannot tell you is therefore essential before ordering one or interpreting the result.
What Is Coeliac Disease?
Coeliac disease is a chronic autoimmune condition triggered by gluten in genetically susceptible people.
Gluten is a group of proteins found mainly in wheat, rye and barley. When someone with coeliac disease eats gluten, their immune system reacts abnormally and damages the lining of the small intestine.
This damage particularly affects the intestinal villi. These are tiny finger-like structures that increase the surface area of the intestine and help the body absorb nutrients from food.
Coeliac disease affects around 1 in 100 people in the UK, although many cases remain undiagnosed. It should not be confused with a wheat allergy or with non-coeliac gluten or wheat sensitivity. These conditions can produce overlapping symptoms, but their biological mechanisms are different.
Once coeliac disease has been properly diagnosed, treatment involves following a strict lifelong gluten-free diet.
One important point should come before that, however: do not normally start a gluten-free diet before diagnostic testing has been completed. Removing gluten can reduce antibody levels and make the condition more difficult to identify.
Antibody Test vs Genetic Test: What Is the Difference?
Although both may be described online as a coeliac disease test, antibody testing and HLA genetic testing measure very different things.
Antibody blood test | HLA genetic test | |
What it looks for | Immune response associated with coeliac disease | Genetic susceptibility |
Main markers | IgA tissue transglutaminase antibodies, usually written IgA-tTG | HLA-DQ2 and HLA-DQ8 |
Typical sample | Blood | Blood or cheek cells, depending on the laboratory |
Do you need to be eating gluten? | Yes | No |
Can it help diagnose active disease? | Yes, as part of the medical diagnostic pathway | Not by itself |
Value of a negative result | Depends on gluten intake, IgA status and clinical context | Particularly useful for making coeliac disease very unlikely |
Value of a positive result | Can provide strong diagnostic evidence | Shows susceptibility only |
In England, initial medical testing generally relies on IgA tissue transglutaminase antibodies together with total IgA measurement. HLA typing is not normally used as the first test for someone who is eating gluten and has suspected coeliac disease.
Coeliac Blood Tests: Looking for an Immune Response to Gluten
When a person with coeliac disease consumes gluten, the immune system can produce characteristic autoantibodies.
The main marker used for initial testing is IgA tissue transglutaminase antibody, commonly abbreviated to:
IgA-tTG;
tTG-IgA;
IgA anti-TG2.
In England, this is normally assessed alongside the person's total IgA concentration.
If the result suggests coeliac disease, further specialist assessment may be required before the diagnosis is considered confirmed.
Why Are Total IgA Levels Checked as Well?
Some people have selective IgA deficiency, meaning that their body produces very little or no immunoglobulin A.
This matters because a person with IgA deficiency may have coeliac disease but still produce a negative IgA-tTG result.
In such situations, clinicians can use IgG-based antibody tests instead.
This is one reason a home test that measures a limited number of markers should not automatically be treated as equivalent to a complete laboratory investigation.
A negative result only has meaning when the test used, gluten intake and the person's immunoglobulin status are taken into account.
How Does a Home Coeliac Disease Test Work?
Some home coeliac tests sold online or through pharmacies use a small blood sample collected from the fingertip.
The exact contents vary between products, but a kit may contain:
a sterile lancet;
a blood collection device;
buffer solution;
a test cassette;
instructions for use.
A typical procedure may involve:
washing and thoroughly drying your hands;
preparing or cleaning the fingertip as instructed;
using the lancet to produce a blood drop;
collecting the required amount of blood;
mixing it with the supplied solution if required;
placing the sample onto the test cassette;
waiting for the specified reaction time;
reading the result within the time window given by the manufacturer.
Always follow the instructions supplied with the specific device. Blood volume, buffer quantity and reading time can differ from one test to another.
What Do the C and T Lines Mean?
Many rapid immunochromatographic tests use two possible lines.
The C line is the control line. It confirms that the test has run correctly.
The T line represents the test reaction.
Depending on the manufacturer's instructions:
a C line plus a T line generally indicates a positive result;
a C line alone generally indicates a negative result;
no C line normally means the test is invalid.
A faint T line may still count as positive. The manufacturer's instructions should always take priority when reading the cassette.
More importantly, however, a positive home coeliac test should not be regarded as a final medical diagnosis.
A positive result should be followed by formal testing and clinical assessment.
Why Must You Still Be Eating Gluten Before a Coeliac Blood Test?
Coeliac serology depends on an immune response to gluten.
If you significantly reduce or completely remove gluten before testing, antibody concentrations can gradually fall. Eventually, a blood test may become negative even though the person genuinely has coeliac disease.
For this reason, diagnostic blood testing should normally be performed while gluten is still being consumed.
Do not start a gluten-free diet simply because you suspect coeliac disease or because you are waiting for a test.
If you have already avoided gluten for several weeks or months, speak to your GP or specialist before attempting to reintroduce it yourself. Depending on your history, they may discuss a medically supervised gluten challenge or an alternative diagnostic strategy.
What Should You Do After a Positive Home Coeliac Test?
A positive home test means that the antibodies targeted by that particular device have been detected.
The next step is not to diagnose yourself or immediately eliminate gluten.
Instead, speak to your GP.
Formal laboratory serology can then be arranged, and the result can be interpreted alongside:
your symptoms;
family history;
current gluten intake;
total IgA concentration;
other blood results;
possible nutritional deficiencies.
If the laboratory findings support coeliac disease, referral to gastroenterology may follow.
Can Coeliac Disease Be Diagnosed Without a Biopsy in England?
This has changed significantly.
The 2026 British Society of Gastroenterology guidelines now recognise an optional no-biopsy pathway for selected symptomatic adults.
Where an adult assessed in secondary care has an IgA-tTG result at least 10 times the upper limit of normal, symptoms consistent with coeliac disease and no separate clinical reason for an upper gastrointestinal endoscopy, diagnosis may in some cases be made without duodenal biopsy.
The decision should be made with a gastroenterologist rather than from a home test or GP result alone.
You can read the scientific recommendations in the 2026 British Society of Gastroenterology guidelines on adult coeliac disease.
For adults who do not meet the appropriate criteria, endoscopy with duodenal biopsies remains an important part of diagnosis.
Children follow a separate paediatric diagnostic pathway and should be assessed through paediatric services rather than by applying adult criteria.
What If a Home Coeliac Test Is Negative?
A negative test reduces the likelihood that the antibodies detected by that device are present. It does not always rule out coeliac disease.
Several factors can produce or contribute to a misleading negative result:
you have already reduced or stopped gluten;
you have IgA deficiency;
too little blood was collected;
the test was performed incorrectly;
the device has limited sensitivity;
the disease is seronegative, which is uncommon but possible.
If symptoms continue despite a negative home test, medical testing may still be appropriate.
A home result should not override persistent symptoms, unexplained deficiencies, family history or other clinical reasons for investigating coeliac disease.
What Does a Coeliac Genetic Test Look For?
A genetic coeliac test works differently from antibody testing.
Coeliac disease has a particularly strong association with variants within the human leukocyte antigen, or HLA, system.
The main genetic profiles are known as:
HLA-DQ2;
HLA-DQ8.
More detailed analysis may identify combinations such as:
HLA-DQ2.5;
HLA-DQ2.2;
HLA-DQ8.
These profiles are determined from variants in HLA genes, particularly HLA-DQA1 and HLA-DQB1.
Almost everyone who develops coeliac disease carries a compatible HLA background. However, the reverse is not true.
HLA-DQ2 and HLA-DQ8 are common in European populations. Roughly 30–40% of people may carry one or more of these susceptibility profiles, while only a small proportion will ever develop coeliac disease.
That leads to one of the most important rules when interpreting a genetic coeliac test:
HLA positive does not mean you have coeliac disease.
It means that the genetic background required for the disease is present.
Why Is a Negative HLA Test More Useful Than a Positive One?
The main clinical value of HLA testing lies in its ability to exclude coeliac disease.
If the relevant HLA-DQ2 and HLA-DQ8 susceptibility profiles are absent, coeliac disease becomes highly unlikely.
This gives HLA typing a strong negative predictive value.
The result can therefore be summarised in a simple way:
HLA negative: coeliac disease is very unlikely.
HLA positive: coeliac disease remains possible, but the result does not show whether the disease is present.
This distinction explains why HLA testing is generally much better at answering the question “Can coeliac disease reasonably be ruled out?” than “Do I have coeliac disease?”
How Is an HLA Genetic Test Performed?
HLA typing can be carried out using blood or, depending on the laboratory, cells collected from inside the cheek.
With a home cheek-swab test, the collection process is usually straightforward.
The laboratory may ask you to avoid eating, drinking, smoking or brushing your teeth for a specified period before taking the sample.
You then rub the swab firmly against the inside of the cheek for the required length of time. Some kits use more than one swab to ensure that enough cells are collected.
The swabs are labelled and returned to the laboratory.
Once received, the laboratory:
extracts DNA from the cells;
analyses the relevant HLA variants;
determines which HLA-DQ profiles are present;
produces a genetic report.
Depending on the laboratory, this can involve PCR, genotyping or sequencing technologies.
There is no universal turnaround time. It depends on the analytical method, laboratory workload and service purchased.
If you want to understand more broadly how DNA analysis can be applied to nutritional traits, our guide to DNA testing and diet explains genetic sampling, analysis and the limits of nutrigenetic interpretation.
How Should You Interpret a Positive HLA-DQ2 or HLA-DQ8 Result?
A report may state that you carry HLA-DQ2.5, HLA-DQ2.2, HLA-DQ8 or another relevant combination.
That result shows genetic susceptibility.
It does not tell you:
whether your small intestine is currently damaged;
whether coeliac antibodies are present;
whether your current symptoms are caused by coeliac disease;
whether you will develop coeliac disease in the future.
If symptoms or other clinical findings suggest coeliac disease, antibody testing and potentially further investigation may still be required.
It is also important not to confuse coeliac disease with other reactions to food.
Coeliac disease, wheat allergy, lactose intolerance, non-coeliac wheat sensitivity and other food-related symptoms have different causes and require different forms of investigation.
Our guide to food intolerance testing explains these distinctions in more detail.
Can Coeliac Disease Risk Be Determined from a Single SNP?
Some consumer genetic reports focus on individual SNPs.
A SNP, or single nucleotide polymorphism, is a variation at one specific position in the DNA sequence.
Variants such as rs2187668 and rs7454108 have been used in genetic studies or as proxies for particular HLA backgrounds.
However, they should not be oversimplified into claims such as:
“CC means you tolerate gluten.”
or:
“TT means you are gluten intolerant.”
That is not how coeliac disease genetics works.
HLA susceptibility depends on combinations of variants and alleles. The quality of a genetic interpretation therefore depends on:
which variants were tested;
whether the main HLA risk profiles were properly captured;
the laboratory method;
the quality of the reference data;
how the result was interpreted.
Before ordering a genetic coeliac test, check whether the laboratory actually assesses the main HLA-DQ2 and HLA-DQ8 susceptibility profiles rather than relying on one or two isolated markers.
When Can HLA Genetic Testing Be Useful?
HLA testing is not normally recommended as the routine first investigation for someone who is eating gluten and can undergo standard antibody testing.
Its main value appears in more specific diagnostic situations.
You Stopped Eating Gluten Before Being Tested
This is one of the clearest examples.
Once gluten has been removed from the diet, antibody levels can fall and intestinal damage may begin to heal. Standard tests can therefore become increasingly difficult to interpret.
HLA testing is unaffected by diet because your genetic profile does not change when you stop eating gluten.
If the relevant HLA susceptibility profiles are absent, coeliac disease becomes very unlikely. This may help avoid an unnecessary gluten challenge.
If HLA-DQ2 or HLA-DQ8 is present, however, the diagnosis remains unresolved.
Your Blood Tests and Biopsy Do Not Agree
Occasionally, the different components of the investigation do not fit neatly together.
For example:
antibodies may be positive but biopsies inconclusive;
intestinal changes may be present but serology negative;
a person may already have been on a gluten-free diet before investigation.
HLA typing can provide an additional piece of evidence in these situations.
A Close Relative Has Coeliac Disease
First-degree relatives of someone with coeliac disease have a higher risk than the general population.
Screening may therefore be appropriate even when symptoms are absent.
This does not mean every relative needs to buy a genetic test.
Depending on age, symptoms, gluten intake and medical history, clinicians may recommend serology, HLA typing, later retesting or another strategy.
Testing a Child
It would be incorrect to assume that genetic testing is automatically better than serology in young children.
Children with suspected coeliac disease should follow an appropriate paediatric diagnostic pathway.
The role of antibody testing, HLA typing and biopsy depends on the individual situation and should be determined with paediatric or gastroenterology services.
Which Coeliac Disease Test Should You Choose?
The most appropriate test depends mainly on your current diet and why you are testing.
You Have Symptoms and Still Eat Gluten
Start with medical serology.
In England, IgA-tTG together with total IgA is generally far more useful for identifying active coeliac disease than a standalone genetic test.
A positive result can then be assessed through the appropriate specialist pathway.
You Are Already on a Gluten-Free Diet
Serology becomes more difficult to interpret once gluten exposure has been reduced.
HLA typing can be useful here.
A negative result for the relevant HLA profiles makes coeliac disease very unlikely.
A positive result does not establish the diagnosis. Your clinician may then discuss whether further testing or a supervised gluten challenge is appropriate.
A Close Relative Has Coeliac Disease
Testing may be appropriate even without obvious symptoms.
The best strategy depends on factors such as:
age;
whether you currently eat gluten;
previous test results;
symptoms;
other medical conditions.
Your Serology and Biopsy Results Conflict
This is one of the situations where HLA testing can be particularly valuable.
A negative HLA result can strongly argue against coeliac disease, whereas a positive result simply keeps the diagnosis possible.
Coeliac Disease Testing in England: How the Medical Pathway Works
In England, it is useful to distinguish between three very different types of testing:
a home antibody test;
laboratory serology ordered as part of medical assessment;
HLA genetic testing.
They are not interchangeable.
If coeliac disease is suspected while you are still eating gluten, the usual starting point is blood testing for IgA-tTG and total IgA.
A positive result should lead to appropriate clinical assessment rather than immediate self-treatment.
The 2026 BSG adult guideline has changed the traditional assumption that every adult with coeliac disease must undergo an endoscopy and biopsy.
Selected symptomatic adults with IgA-tTG levels at least ten times the upper limit of normal may now be considered for a specialist no-biopsy diagnosis when there is no other reason for endoscopy.
For many other adults, however, duodenal biopsy remains appropriate.
HLA testing is mainly used when the diagnostic picture is uncertain, particularly when someone has already stopped gluten or when blood tests, symptoms and histology do not agree.
A privately purchased genetic result can provide useful information, but it should not be confused with a complete clinical diagnosis.
For a broader overview of genetic and health-related testing, you can also explore the English version of InfoTestADN.
Genetic Test or Antibody Test: What Should You Remember?
There is no single coeliac disease test that answers every question.
An antibody test looks for an immune response associated with active disease. It is most informative when the person is still eating gluten and is the usual starting point for medical investigation.
An HLA-DQ2/DQ8 genetic test answers a different question: does the person have the genetic background that makes coeliac disease possible?
Its greatest strength is a negative result.
If the relevant HLA profiles are absent, coeliac disease becomes highly unlikely.
If they are present, no diagnosis can be made from genetics alone because these variants are common in the general population.
Home tests can provide useful preliminary information, but persistent symptoms, a positive antibody result or an unclear genetic report should be interpreted within a medical pathway.
Most importantly, avoid starting a gluten-free diet solely on the basis of an online test if coeliac disease has not yet been properly investigated. Removing gluten too early can make the diagnosis harder to establish.
Does a Positive Coeliac Genetic Test Mean I Have Coeliac Disease?
No.
HLA-DQ2 and HLA-DQ8 are common in European populations. Carrying one of these profiles means that you have a genetic susceptibility compatible with coeliac disease, not that you have active disease.
Antibody testing and, where appropriate, further clinical investigation are needed to diagnose coeliac disease.
Can a Negative HLA Test Rule Out Coeliac Disease?
In most cases, absence of the main HLA-DQ2 and HLA-DQ8 susceptibility profiles makes coeliac disease highly unlikely.
The usefulness of the result does depend on what the laboratory actually tested, so check that the relevant HLA profiles were included in the analysis.
Should I Stop Eating Gluten Before a Coeliac Blood Test?
No, not unless your healthcare professional specifically advises you to do so.
Reducing or eliminating gluten can lower antibody levels and potentially cause a false-negative or difficult-to-interpret result.
Is a Positive Home Coeliac Test Enough to Start a Gluten-Free Diet?
No.
A positive home test should be followed by formal medical assessment. Starting a gluten-free diet immediately can affect later blood tests and biopsy findings.
Can I Be Tested for Coeliac Disease If I Already Avoid Gluten?
Yes, but the diagnostic strategy may need to change.
HLA typing can be particularly useful because genetics are unaffected by your diet. A negative HLA result can make coeliac disease very unlikely, while a positive result means further assessment may still be necessary.