Most heavily advertised food intolerance tests — IgG antibody panels at £50–£300 — are not clinically validated: NHS guidance and UK allergy bodies say IgG antibodies show exposure to foods, not intolerance. What does work: supervised elimination diets (the gold standard, near-free), hydrogen breath tests at £150–£300 for lactose and similar intolerances, and coeliac blood testing before any gluten-free experiment.
- ✓IgG food intolerance tests aren't validated — UK and international allergy bodies advise against them.
- ✓The gold standard is a supervised elimination diet: remove, monitor, reintroduce, confirm.
- ✓Hydrogen breath tests (£150–£300) genuinely diagnose lactose intolerance; test for coeliac before cutting gluten.
The tests that don't work — despite the marketing
Walk into a pharmacy or search online and the food intolerance products you'll meet first are IgG antibody tests: a finger-prick sample, £50–£300, and a report scoring your "reactivity" to 100+ foods. The marketing is polished. The clinical position is not ambiguous: the NHS, the British Dietetic Association, and allergy bodies in the UK, Europe and the US advise against using IgG tests to diagnose food intolerance.
The reason is biology, not turf protection. IgG antibodies to foods are a normal immune response to eating those foods — they indicate exposure and probably tolerance, not a problem. Test anyone against 100 foods and the report will flag plenty, typically the things they eat most (wheat, dairy, egg, yeast are perennial "positives"). Acting on it means cutting staple foods on the strength of a measurement that was never abnormal.
- The harm is real, not theoretical. Long exclusion lists lead to needlessly restricted diets, nutritional gaps, food anxiety — and in children, where these tests are sometimes marketed to worried parents, genuine growth and feeding risks.
- The same verdict covers the wider shelf: hair analysis, kinesiology, Vega (electrodermal) testing and "bioresonance" have no diagnostic validity for food intolerance. None is recommended by any UK clinical body.
- The tell: validated tests answer narrow questions; unvalidated ones promise to screen everything at once. A 100-food panel is a marketing format, not a diagnostic one.
First, know which question you're asking
"Food intolerance" gets used as one bucket for three different problems, and the right test depends on which you actually have:
| Problem | What it is | How it's properly investigated |
|---|---|---|
| Food allergy | Immune (IgE) reaction — hives, swelling, wheeze, rapid onset; can be dangerous | IgE blood tests and skin-prick testing, interpreted by an allergy clinic — see our allergy testing guide |
| Coeliac disease | Autoimmune reaction to gluten damaging the gut — not an intolerance | Blood test (tTG-IgA) then biopsy — while still eating gluten |
| Food intolerance | Non-immune digestive trouble — bloating, pain, wind, diarrhoea, slower onset | Elimination and reintroduction; hydrogen breath tests for specific sugars |
The distinctions carry real stakes. Allergy can be dangerous and deserves proper clinic assessment, not a postal kit. Coeliac disease affects roughly 1 in 100 people, most undiagnosed — and its test only works if you're still eating gluten, which is why going gluten-free "to see" before testing is the classic self-experiment mistake. Genuine intolerance, meanwhile, is unpleasant but not dangerous — and it's diagnosed by structured eating, not blood.
The routes that actually work
The validated toolkit is short, cheap and effective:
- The elimination-and-reintroduction diet — the gold standard. Keep a food and symptom diary for a couple of weeks, remove the suspected food completely for 2–6 weeks, then reintroduce it deliberately and watch what happens. Symptoms that vanish on exclusion and return on reintroduction are a diagnosis no blood test can match. Cost: effectively nothing. Best done with a registered dietitian (£60–£120 privately per session) — especially for multi-food suspicion or a low-FODMAP trial, which shouldn't be a permanent DIY diet.
- Hydrogen breath tests — for the sugar intolerances. Lactose intolerance (and related problems like fructose malabsorption or bacterial overgrowth) can be genuinely diagnosed by measuring hydrogen in your breath after a test dose. Private clinics charge roughly £150–£300; it's a two-to-three-hour appointment and properly validated.
- Coeliac serology — before any gluten experiment. A tTG-IgA blood test costs about £30–£60 privately (free via your GP with symptoms) and screens reliably for coeliac disease — provided gluten is still in your diet, usually for at least six weeks beforehand.
- A GP or gastroenterologist when symptoms persist. Ongoing gut trouble deserves the ruling-out pathway — coeliac testing, calprotectin, sometimes endoscopy — before any food gets the blame. Red flags (bleeding, weight loss, onset over 50) go straight to a doctor.
With health insurance, the clinical parts of this — GP and specialist consultations, coeliac and breath testing where a clinician orders it, dietitian referrals on some policies — are generally covered under outpatient benefits when you're investigating symptoms. The £120 IgG kit, by contrast, is covered by no policy, for the same reason no NHS clinic orders one.
Symptoms worth more than a mail-order verdict?
A practical plan (and what to spend)
Pulling it together into the order that saves money and gets answers:
- Week 1–2: diary, £0. Log food, symptoms and timing. Patterns often emerge that point at a culprit — or at non-food factors like stress, alcohol or eating speed.
- If gluten is a suspect: coeliac blood test, £30–£60 (or free at your GP) — before changing your diet.
- If dairy is a suspect: trial exclusion, then consider a breath test, £150–£300 if you want objective confirmation rather than relying on the trial alone.
- Then: one-food-at-a-time elimination and reintroduction, ideally with a dietitian if multiple foods are in the frame.
- Persistent or worrying symptoms: clinician first — NHS GP, or private GP/gastroenterologist within days if speed matters.
Total spend on the evidence-based path: often under £100, occasionally £300–£500 with a breath test and dietitian sessions — usually less than a single large IgG panel plus the supplements its report tends to recommend.
None of this is to dismiss how real the symptoms are — food intolerance is common and can be miserable. That's exactly why it deserves methods that produce true answers. The IgG industry sells certainty in two weeks; the boring route delivers it in six — and the food list it hands back is usually far shorter.
Frequently asked questions
Do food intolerance blood tests actually work?
The IgG antibody tests sold for £50–£300 don't — the NHS, the British Dietetic Association and UK and international allergy bodies all advise against them, because IgG antibodies indicate you've eaten a food, not that you react to it. The tests that genuinely work are narrower: hydrogen breath tests for sugar intolerances, coeliac serology for gluten, and supervised elimination diets for everything else.
Why are IgG food intolerance tests not recommended?
Because IgG antibodies to foods are a normal immune response to eating them — arguably a marker of tolerance. Testing anyone against 100 foods flags plenty of harmless "reactions", typically their dietary staples. Acting on the results means cutting foods unnecessarily, risking nutritional gaps and food anxiety — with particular concern where these tests are marketed for children. No UK clinical body endorses them.
What's the difference between a food intolerance and a food allergy?
Allergy is an immune (IgE) reaction — hives, swelling, wheeze, typically within minutes — and can be dangerous; it's tested with IgE bloods and skin-prick tests at an allergy clinic. Intolerance is non-immune digestive trouble — bloating, pain, wind, hours later — and isn't dangerous; it's diagnosed by elimination and reintroduction or breath testing. Rapid-onset or severe reactions always warrant proper allergy assessment.
How does a hydrogen breath test for food intolerance work?
You drink a measured dose of the sugar under investigation — lactose, most commonly — and breathe into a device at intervals over two to three hours. If your gut can't absorb the sugar, bacteria ferment it and produce hydrogen, which appears in your breath. It's a validated diagnostic for lactose intolerance and related problems, costing roughly £150–£300 at private clinics.
How do I do an elimination diet properly?
Diary first: two weeks logging food, symptoms and timing. Then exclude one suspected food completely for 2–6 weeks while keeping the rest of your diet stable. If symptoms improve, reintroduce the food deliberately — the return of symptoms confirms the intolerance; no return means the food was innocent. One food at a time, and use a registered dietitian for multi-food suspicions or low-FODMAP trials.
Should I get tested for coeliac disease before going gluten-free?
Yes — this ordering really matters. The coeliac blood test (tTG-IgA, roughly £30–£60 privately or free via your GP) only works while gluten is in your diet, usually for at least six weeks beforehand. Go gluten-free first and a negative test proves nothing, leaving you stuck eating gluten again for weeks to test properly. Coeliac affects about 1 in 100 people, most undiagnosed.
Are hair, kinesiology or Vega food intolerance tests legitimate?
No. Hair analysis, applied kinesiology (muscle testing), Vega/electrodermal machines and bioresonance have no demonstrated ability to detect food intolerance, and no UK clinical body recommends any of them. They share the same tell as IgG panels: sweeping multi-food verdicts from a test that answers no specific physiological question. Money spent there buys a food list to fear, not a diagnosis.
How much does proper food intolerance testing cost?
Often under £100. The gold-standard elimination diet is free; coeliac serology runs £30–£60 privately (free via a GP); a hydrogen breath test costs £150–£300 if you want objective confirmation of lactose intolerance; dietitian sessions are £60–£120 each. Even the full works — breath test plus a few dietitian sessions — usually totals £300–£500, comparable to one large IgG panel and its supplement upsells.
Will health insurance cover food intolerance testing?
Not IgG kits — no insurer covers tests that clinical guidance rejects. But investigating gut symptoms through the proper route is generally covered with outpatient benefits: private GP and gastroenterologist consultations, coeliac testing, breath tests where a clinician orders them, and dietitian referrals on some policies. Allergy investigation at a clinic is likewise covered territory — see our private allergy testing guide.
When should I see a doctor about suspected food intolerance instead of testing myself?
Straight away if there are red flags: blood in stools, unintended weight loss, symptoms starting over 50, anaemia, or a family history of coeliac or bowel disease. Also when reactions are rapid or severe (possible allergy), when a child is involved, or when symptoms persist despite your elimination experiments. Those situations need the ruling-out pathway — coeliac serology, calprotectin, sometimes endoscopy — not another kit.