Coeliac Disease or Gluten Sensitivity? How to Tell, and Why to Test First
If you suspect gluten is making you ill, the single most important thing you can do is keep eating it until you have been tested. Coeliac disease is diagnosed by measuring your immune response to gluten, and that response fades once you cut gluten out. Go gluten free first and the test can come back falsely negative, leaving a serious autoimmune condition undiagnosed for years.
That one piece of advice is worth more than every gluten free recipe on the internet. This guide explains the difference between coeliac disease, non coeliac gluten sensitivity and wheat allergy, walks through how testing actually works in the UK, and covers what a missed diagnosis can do to your hair.
Do not go gluten free before you are tested
UK guidance is clear: to be tested reliably for coeliac disease you need to have been eating gluten in more than one meal a day for at least six weeks beforehand. If you have already cut it out and you want an answer, speak to your GP before you reintroduce anything, because a gluten challenge should be planned rather than improvised.
Key takeaways
- Coeliac disease is autoimmune, not an intolerance. It affects around 1 in 100 people in the UK, and a large majority are still undiagnosed.
- Three different conditions get confused. Coeliac disease, non coeliac gluten sensitivity and wheat allergy have different mechanisms, tests and consequences.
- Testing starts with a blood test for tTG IgA plus total IgA, followed by a gut biopsy if it is positive.
- Much of what people blame on gluten may be fructans, a fermentable carbohydrate in wheat, which is a different problem with a different solution.
- Undiagnosed coeliac disease can cause hair shedding, usually through iron, B12 and folate deficiency caused by poor absorption.
- A gluten free diet is not healthier by default. If you do not need it, it tends to cost more, deliver less fibre and hide a diagnosis.
Four gluten claims that do not hold up
The case for everyone giving up gluten and grains rests on a handful of arguments that are repeated everywhere and supported nowhere. Each has a grain of truth stretched well past breaking point, and they are worth taking apart before we get to the useful part:
- Wheat has not been bred to contain much more gluten. Analyses comparing wheat cultivars grown across more than a century find no meaningful upward trend in gluten protein content. What has risen sharply is how much wheat we eat and how it is processed.
- Leaky gut is not an established disease. Intestinal permeability is a genuine, measurable phenomenon and it is increased in coeliac disease. It is not a proven cause of general ill health in people without a diagnosed condition, and it does not justify blanket grain avoidance.
- Fortification is a public health success, not a toxin. UK law requires white and brown flour to be fortified with calcium, iron, thiamin and niacin, and folic acid has since been added. This was introduced to prevent deficiency diseases and neural tube defects. There is no evidence it causes inflammation or digestive symptoms.
- Lectins and phytates are overstated. Cooking destroys the great majority of lectins in grains and pulses. Phytates modestly reduce absorption of some minerals and also behave as antioxidants. Neither is a reason for a healthy person to avoid whole grains, which are among the most consistently protective foods in nutrition research.
None of that means gluten never causes problems. It means the reason has to be identified properly, because the answer for coeliac disease is completely different from the answer for a fructan issue.
What is coeliac disease?
Coeliac disease is an autoimmune condition. In people who carry the relevant genes, gluten triggers the immune system to attack the lining of the small intestine. The finger like projections called villi, which do the work of absorbing nutrients, flatten out. That is why the consequences reach so far beyond the gut.
Symptoms vary enormously, which is a large part of why diagnosis is so often delayed:
- Bloating, wind, abdominal pain, diarrhoea or constipation
- Persistent tiredness, often the dominant complaint
- Unexplained iron deficiency anaemia that keeps coming back
- Unintended weight loss, or in children faltering growth and delayed puberty
- Mouth ulcers, and an intensely itchy blistering rash called dermatitis herpetiformis
- Bone thinning, recurrent miscarriage, unexplained infertility
- Tingling or numbness in hands and feet, headaches, low mood
Some people have almost no digestive symptoms at all and are picked up only through a stubborn anaemia or a family screening. That silent presentation still causes intestinal damage.
Coeliac disease, gluten sensitivity or wheat allergy?
| Coeliac disease | Non coeliac gluten sensitivity | Wheat allergy | |
|---|---|---|---|
| Mechanism | Autoimmune | Not established | IgE allergic response |
| Gut damage | Yes, villous atrophy | No | No |
| Blood test | tTG IgA and total IgA | None exists | Specific IgE, skin prick |
| Timing | Hours to days, cumulative | Usually hours | Minutes to two hours |
| Long term risk | Deficiency, osteoporosis, fertility problems | No known long term damage | Anaphylaxis in severe cases |
| Treatment | Strict lifelong gluten free diet | Reduce to your own tolerance | Avoid wheat, allergy plan |
A fourth possibility belongs on that list in practice: irritable bowel syndrome. Symptoms overlap heavily, and the two can coexist, which is another reason self diagnosis is unreliable.
Non coeliac gluten sensitivity: real symptoms, uncertain cause
Plenty of people genuinely feel better without wheat, test negative for coeliac disease and have no allergy. Their symptoms are real. What is not settled is whether gluten is the culprit.
Blinded challenge studies have repeatedly found that when people who believe they react to gluten are given gluten or a placebo without knowing which, many react to both, or to neither. The strongest alternative explanation is fructans, a chain of fructose molecules that wheat happens to be rich in. Fructans are poorly absorbed, travel to the large intestine and are fermented by gut bacteria, producing gas, distension and pain. They belong to the group of fermentable carbohydrates known as FODMAPs.
This distinction has real practical value, because a fructan problem responds to things a gluten free diet does not touch, including portion size, long fermentation and which wheat products you choose. We cover that in detail in our companion article on whether sourdough really is easier to digest, which is the practical shopping and baking side of this question.
How coeliac testing works in the UK
- Keep eating gluten. More than one meal a day containing gluten, for at least six weeks before the test. This is not optional. It is what makes the result meaningful.
- Blood test. Your GP requests tissue transglutaminase IgA, usually written tTG IgA, together with total IgA. The total IgA matters because roughly 1 in 50 people are IgA deficient, which would make the main test read falsely negative.
- A second antibody test such as endomysial antibodies may be added if the first result is borderline.
- Referral for endoscopy. A positive blood test leads to a gastroenterology referral for a biopsy of the small intestine, which remains the confirming test for most adults.
- Diagnosis and follow up. If confirmed, you should be referred to a dietitian, offered annual review, and have bone health assessed. First degree relatives are offered testing too, because their risk is roughly 1 in 10.
Genetic testing for HLA DQ2 and DQ8 is sometimes used, and it is worth understanding what it does. Around a third of the population carries these genes and almost never develops coeliac disease, so a positive result proves very little. A negative result is genuinely useful, because it makes coeliac disease extremely unlikely. It rules out rather than rules in.
Home test kits sold online are not a diagnosis. A positive one still needs your GP, and a negative one is not reassurance if you had already cut down on gluten.
Coeliac disease and your hair
This is a hair and wellbeing blog, and the connection here is one of the more genuinely useful things we can tell you, because hair change is sometimes the symptom that finally gets someone tested.
Damaged villi absorb nutrients poorly. The nutrients most commonly affected are exactly the ones hair depends on:
- Iron. Unexplained, recurring iron deficiency anaemia is one of the classic presentations of undiagnosed coeliac disease. Low ferritin is strongly associated with diffuse shedding, particularly in women.
- B12 and folate. Both are absorbed in the small intestine and both are commonly low at diagnosis.
- Zinc. Deficiency is well recognised in untreated coeliac disease and is associated with hair changes.
- Vitamin D and calcium. Relevant to the bone thinning that often accompanies late diagnosis.
The pattern of shedding this produces is usually telogen effluvium, a diffuse thinning across the whole scalp rather than a receding pattern, and it typically appears two to three months after the underlying problem takes hold. There is also a recognised association between coeliac disease and other autoimmune conditions, including autoimmune thyroid disease and alopecia areata, which causes discrete round patches of loss.
Two practical points follow. First, if you have unexplained diffuse shedding and ongoing digestive symptoms or a stubborn anaemia, ask your GP about coeliac testing rather than reaching for a supplement. Second, do not self treat suspected iron deficiency. Iron should be measured before it is taken, because unnecessary iron is not harmless and, more importantly, treating the anaemia without finding the cause hides the diagnosis that produced it.
For context on how shedding works and what else causes it, see what causes thinning hair and how the hair growth cycle works. Because autoimmune conditions cluster, our guide to thyroid related hair loss is often the other half of this picture, and our guide to blood tests, diet and hair loss lists exactly which results to ask for.
Reading a gluten free label properly
If you are diagnosed, the diet has to be strict, and labels are where that is won or lost.
- Gluten free is a legally controlled claim in the UK and EU. It means the food contains no more than 20 parts per million of gluten, a threshold set because it is tolerated by the overwhelming majority of people with coeliac disease.
- No gluten containing ingredients is a weaker statement. It says nothing about cross contamination during manufacture.
- Allergen labelling. UK law requires cereals containing gluten to be emphasised in the ingredients list, usually in bold. Scan for wheat, barley, rye, spelt, kamut and malt.
- Oats are a special case. Oats do not contain gluten but are very often contaminated in the supply chain, and a small minority of people with coeliac disease also react to avenin, the oat protein. Choose oats specifically labelled gluten free, and introduce them under dietitian guidance.
- Watch the hidden sources: soy sauce, stock cubes, some sausages and processed meats, thickened sauces, beer, and communion wafers.
Kitchen cross contamination checklist
- A separate toaster, or toaster bags, because crumbs are the usual culprit
- Your own butter, jam and spread tubs, kept free of shared knives
- Fresh water for boiling gluten free pasta
- Separate chopping boards and a dedicated colander
- Wooden spoons and scratched plastic boards replaced rather than scrubbed
If you do not have coeliac disease, is gluten free still a good idea?
Usually not, and it is worth being honest about why.
- Cost. Gluten free staples in UK supermarkets routinely cost several times their standard equivalents.
- Fibre. Gluten free breads and pastas are often lower in fibre and whole grain, and low fibre intake is one of the clearest dietary risks we know of.
- Formulation. Removing gluten costs a manufacturer structure and mouthfeel, which is frequently replaced with more fat, sugar and starch.
- It hides the answer. The most serious cost of all. A restricted diet that partly works can keep you from the test that would have explained everything.
If wheat genuinely disagrees with you and coeliac disease has been excluded, a more targeted approach usually beats blanket avoidance: adjust portion sizes, favour slowly fermented breads, and consider a short structured low FODMAP trial supervised by a dietitian rather than an open ended elimination.
Frequently asked questions
Can I be tested for coeliac disease if I already stopped eating gluten?
Not reliably. The antibodies the test measures fall once gluten is removed, so the result can be falsely negative. UK guidance is to eat gluten in more than one meal a day for at least six weeks before testing. If you have already stopped, speak to your GP about a planned gluten challenge rather than reintroducing it on your own.
What is the difference between coeliac disease and gluten intolerance?
Coeliac disease is an autoimmune condition in which gluten causes measurable damage to the small intestine, and it requires a strict lifelong gluten free diet. Non coeliac gluten sensitivity causes symptoms without antibodies or gut damage, has no diagnostic test, and is managed by reducing intake to your own tolerance.
Can coeliac disease cause hair loss?
Indirectly, yes. Untreated coeliac disease impairs absorption of iron, B12, folate and zinc, and those deficiencies are associated with diffuse shedding known as telogen effluvium. Coeliac disease is also associated with other autoimmune conditions including alopecia areata. Hair usually improves once the diet is established and deficiencies are corrected under medical supervision.
How common is coeliac disease in the UK?
It affects roughly 1 in 100 people, but a large majority remain undiagnosed. First degree relatives of someone with coeliac disease have a risk of around 1 in 10 and should be offered testing.
Does modern wheat contain more gluten than it used to?
Studies comparing wheat cultivars grown over more than a century do not show a meaningful increase in gluten protein content. What has changed is how much wheat we eat, and how quickly modern industrial bread is fermented.
Are oats safe if I have coeliac disease?
Pure oats do not contain gluten, but they are frequently contaminated during growing and milling, so only oats labelled gluten free should be used. A small minority of people with coeliac disease also react to avenin, the oat protein, so oats are best introduced with dietitian guidance.
Should I take iron supplements if I think gluten is causing my hair to shed?
Not without a blood test. Iron should be measured before it is taken, and treating anaemia without identifying the cause can delay a diagnosis such as coeliac disease. Ask your GP for a full blood count and ferritin alongside coeliac testing.
Is a gluten free diet healthier for everyone?
No. For people without coeliac disease, wheat allergy or a demonstrated sensitivity, going gluten free usually costs more, often reduces fibre and whole grain intake, and can mask a diagnosis. Whole grains are consistently associated with better health outcomes in the research.
The bottom line
Gluten is not a poison, and it is not harmless to everyone either. The useful question is not whether to give it up but which of three quite different conditions you might have, and there is a proper order to finding out: keep eating gluten, ask your GP for tTG IgA and total IgA, and let the result guide the diet rather than the other way round.
If the answer turns out to be coeliac disease, the diet is strict but the recovery is real, and that includes the tiredness, the anaemia and very often the hair.
A note on products. We have deliberately not recommended a supplement on this page. Coeliac disease is a medical condition, deficiencies need to be measured before they are treated, and no shampoo or gummy addresses malabsorption. Watermans has made vegan, cruelty free haircare in the UK since 2012, with over five million bottles sold, and our products are cosmetic support for the hair you have while your GP deals with the cause. If you have persistent digestive symptoms, unexplained tiredness, recurring anaemia or sudden hair shedding, please book an appointment.
