Food intolerance assessment (Assessment of suspected food intolerance)

A careful assessment of symptoms linked to food, to tell true intolerance from food allergy and other causes, and to plan a sensible, evidence-based approach — not a high-street 'intolerance' blood test.

✓ Medically reviewed by a GMC-registered consultant · last reviewed September 2026 · next review September 2027 · how we review

In short

Food intolerance is trouble digesting or handling foods — uncomfortable but not an allergy and not life-threatening.
There is no reliable blood test for food intolerance; high-street IgG 'intolerance' tests are not recommended and can mislead.
Assessment relies on your history, a food and symptom diary, and a carefully supervised elimination and reintroduction trial.
Other conditions, such as coeliac disease, IBS or true food allergy, must be considered, and diets should not be over-restricted without good reason.

A plain-English summary. The detail — including risks and recovery — is below.

At a glance

TypeAssessment of food-related symptoms

AnaestheticNot needed

How long it takesAbout 30–45 minutes, often with dietitian input

Hospital stayOutpatient

Time off workUsually none

When you'll see resultsA plan, often involving a supervised food and symptom diary or elimination trial, is agreed at the appointment

On the NHS?Available on the NHS when clinically indicated; private dietitian-led assessment is also common

A general guide. Your specialist will give you advice for your situation.

Best fit

A clear, honest explanation of what is and is not causing your symptoms

Pause if

IgG or other high-street 'food intolerance' blood tests are not valid and should not guide your diet.

Main recovery point

You leave with an explanation and a plan, often to keep a food and symptom diary or to start a supervised elimination of a suspected food.

Good aftercare

A clear, supervised plan with reintroduction and review built in.

Same day

You leave with an explanation and a plan, often to keep a food and symptom diary or to start a supervised...

First 2–6 weeks

You follow the elimination plan and record symptoms. Any validated tests (such as coeliac or lactose tests) are...

Reintroduction phase

Foods are reintroduced one at a time under guidance to see whether symptoms genuinely return, which is the real...

Review

The findings are reviewed, a longer-term eating plan is agreed, and other conditions are followed up if needed.

Medical line illustration of oral food challenge for Food intolerance assessment. — Illustration only - not a diagnosis, medical advice or a promise of result. Your anatomy and treatment plan may differ. Vuemedics does not publish before-and-after photos.

What is a food intolerance assessment?

Food intolerance means your body has trouble digesting or handling certain foods, causing symptoms such as bloating, wind, tummy pain or diarrhoea. It is uncomfortable but, unlike food allergy, it does not involve the immune system causing a sudden reaction, and it is not life-threatening.

A food intolerance assessment is a careful appointment, often involving a dietitian, to work out whether food is really the cause, which foods, and whether it is intolerance, allergy or another condition (such as irritable bowel syndrome or coeliac disease) that needs different management.

Importantly, there is no reliable blood test for food intolerance. High-street and online 'food intolerance' blood tests — usually measuring IgG antibodies — are not recommended by Allergy UK or the British Society for Allergy and Clinical Immunology. IgG antibodies to food are found in healthy people without symptoms and simply reflect what you eat, so these tests cannot diagnose intolerance and can lead to unnecessary, restrictive diets.

Instead, the assessment relies on your history, a structured food and symptom diary, and, where appropriate, a carefully supervised elimination and reintroduction trial. The aim is to ease symptoms and protect your nutrition, not to label long lists of foods as 'positive'.

Types, options & approaches

There may be different ways to do this. The right approach depends on the clinical question and your circumstances.

History and symptom review

A detailed look at your symptoms, their timing in relation to foods, your diet and any other gut or health problems, to judge whether food is really the cause.

Food and symptom diary

A structured record of what you eat and the symptoms that follow, often over a couple of weeks, which is far more useful than any 'intolerance' blood test.

Supervised elimination and reintroduction

Removing a suspected food for a set period (often 2–6 weeks) and then reintroducing it, under dietitian guidance, to see whether symptoms genuinely change.

Targeted tests for specific conditions

Validated tests where indicated — for example coeliac blood tests, or a hydrogen breath test for lactose intolerance — which are different from unproven 'intolerance' panels.

Checking it is not an allergy

Assessing for true food allergy where the history suggests it, since allergy needs a different, safety-focused approach.

Food intolerance versus food allergy

	Food intolerance	Food allergy
Immune system involved	No	Yes
Typical symptoms	Bloating, wind, tummy pain	Hives, swelling, breathing problems
Can it be life-threatening	No	Yes — can cause anaphylaxis
Useful test	Diary / supervised trial	Skin-prick or specific IgE, with history

Intolerance and allergy are different. If you have ever had swelling, hives or breathing difficulty with a food, that points to allergy and needs urgent, separate assessment.

Preparing for your test

Keep a detailed food and symptom diary before the appointment, noting what you eat and when symptoms occur.
Do not cut out major food groups beforehand without advice, as this can affect tests and your nutrition.
If coeliac disease is being considered, keep eating gluten until tested, as stopping it can hide the diagnosis.
List any other gut symptoms, weight loss, or changes in bowel habit, which may point to another condition.
Note whether you have ever had hives, swelling or breathing problems with food, which suggest allergy, not intolerance.
Bring results of any tests you have already had, including any high-street 'intolerance' tests, so they can be put in context.
Bring a list of your medicines and supplements.

What happens

The clinician or dietitian takes a careful history of your symptoms, your diet, and how the two relate. They consider whether the picture fits intolerance, allergy, or another condition such as IBS or coeliac disease.

Rather than ordering an 'intolerance' blood test, they will usually ask you to keep a food and symptom diary and may plan a supervised elimination and reintroduction of a suspected food. Validated tests are used only where they fit, for example coeliac blood tests or a hydrogen breath test for lactose intolerance.

You leave with an explanation, a clear plan, and advice on keeping your diet balanced. If true allergy or another condition is suspected, you are directed to the right pathway.

Is this test right for me?

A good consultation should explore whether it's the right choice for you now — including reasons to wait or consider something else.

May not be suitable if…

IgG or other high-street 'food intolerance' blood tests are not valid and should not guide your diet.
Hair analysis, applied kinesiology and 'vega' testing have no evidence base and are not recommended.
If your reactions involve swelling, hives or breathing problems, intolerance testing is the wrong pathway — you need allergy assessment.
Self-directed elimination diets without support risk nutritional harm and missed diagnoses.

Delay or rearrange if…

You have red-flag gut symptoms (weight loss, bleeding, difficulty swallowing) that need assessment first.
Coeliac disease is being considered and you have already cut out gluten — testing may need you to reintroduce it first.
You are acutely unwell with a gut infection, which can confuse the picture.
You are pregnant or have another condition where restrictive diets need careful planning.

Alternatives to discuss

A structured food and symptom diary instead of any 'intolerance' test.
Validated tests for specific conditions, such as coeliac serology or a lactose breath test.
Dietitian-led management for IBS, such as a supervised low-FODMAP approach.
Allergy assessment if a true food allergy is suspected.
Watchful waiting and simple dietary adjustments for mild, intermittent symptoms.

Before you decide

Use this as a shared-decision checklist. The aim is not just “can this be done?”, but whether it is right for you, now, with the risks and alternatives clearly understood.

What matters most to me?

Think about symptoms, daily life, work, caring responsibilities, sport, fertility, travel, appearance and anxiety — the right choice depends on your priorities, not just the medical facts.

What are all my options?

Ask about waiting, monitoring, medicines, rehabilitation, a smaller or larger procedure, a different test, NHS referral, or a second opinion where that would help.

What would make me pause?

Active infection, pregnancy, unstable medical problems, smoking, medicines that increase bleeding, poor support at home, or feeling pressured are all reasons to slow down and get tailored advice.

What happens if I do nothing today?

For some problems, waiting is safe; for others, delay can make treatment harder. A good consultation should explain the trade-off in plain English.

Benefits

A clear, honest explanation of what is and is not causing your symptoms
Avoiding unnecessary, restrictive diets driven by unproven tests
A structured, supervised way to identify foods that genuinely cause symptoms
Checking for other treatable conditions such as coeliac disease or lactose intolerance
Protecting your nutrition while you investigate symptoms
Clear direction to allergy assessment if a true allergy is suspected

Risks & complications

More common

Frustration that there is no quick blood test to label your intolerances
Symptoms that fluctuate, making the cause harder to pin down
The effort of keeping a detailed diary and following an elimination trial

Less common

Nutritional gaps if foods are cut out without proper guidance
Needing further tests if another condition is suspected
Symptoms not improving, suggesting food is not the main cause

Rare but serious

Missing a true food allergy if symptoms are wrongly assumed to be intolerance
Missing a serious gut condition if warning symptoms are not acted on

The biggest risks come from unproven 'intolerance' tests and from over-restricting your diet, which can cause nutritional harm and anxiety without fixing symptoms. Make sure any food you cut out is reintroduced and tested properly. Tell the clinician about any weight loss, blood in your stools, or reactions involving swelling or breathing, which need different, sometimes urgent, assessment.

Published figures to discuss

There is no validated diagnostic test for food intolerance, so 'accuracy' is the central issue: unproven IgG tests generate many meaningless positives because IgG to food is normal. Validated tests for specific conditions (coeliac, lactose) have their own, separate performance. The most reliable approach is a supervised diary and elimination–reintroduction trial.

Figure	Reported range	How to interpret it	Source / confidence
Positive IgG 'food intolerance' results in people without symptoms	Common — found in healthy people	IgG to food reflects exposure, not intolerance, which is why these tests are not recommended.	Guide sourcesClinical context
Symptoms ultimately explained by a functional cause such as IBS	Common in clinic populations	Normal validated tests often point to IBS, which can still be managed effectively.	Guide sourcesClinical context
Nutritional harm from restrictive exclusion diets	A practical risk, especially with multiple exclusions or eating-disorder vulnerability	Exclusion and reintroduction should be structured, time-limited and ideally dietitian-supported.	British Dietetic Association — Food allergy and intolerance testingbda.uk.comSource-linked context
Missing coeliac disease before starting a gluten-free diet	Clinically important because testing becomes unreliable after gluten avoidance	Coeliac blood tests usually need you to be eating gluten; do not start long-term gluten avoidance before proper testing unless advised.	Guide sourcesClinical context

These are literature figures, not a personalised prediction. Your own risks and likely benefits depend on your circumstances, your health, and how your care is carried out and followed up.

What happens afterwards

There is no physical recovery from the appointment. 'Afterwards' is about following the diary or elimination plan, watching how symptoms respond, and reviewing the findings.

Same day

You leave with an explanation and a plan, often to keep a food and symptom diary or to start a supervised elimination of a suspected food.

First 2–6 weeks

You follow the elimination plan and record symptoms. Any validated tests (such as coeliac or lactose tests) are arranged and results return.

Reintroduction phase

Foods are reintroduced one at a time under guidance to see whether symptoms genuinely return, which is the real test of intolerance.

Review

The findings are reviewed, a longer-term eating plan is agreed, and other conditions are followed up if needed.

What's normal — and not a worry

Symptoms that take a few weeks to settle on an elimination trial
Needing to reintroduce foods carefully rather than avoiding them forever
Some trial and error before the pattern becomes clear
Realising the cause may be a condition such as IBS rather than a specific food

Aftercare

Follow the food and symptom diary or elimination plan as agreed.
Reintroduce foods one at a time under guidance — do not leave foods out indefinitely without review.
Keep your diet balanced; ask about substitutes if a staple food is removed.
Do not rely on high-street 'intolerance' tests to guide what you eat.
Seek separate, urgent assessment if you ever react to food with swelling or breathing problems.
Report any weight loss, blood in stools or persistent change in bowel habit.
Attend review so the plan can be confirmed and your nutrition checked.

Before your test

Detailed food and symptom diary kept
Elimination and reintroduction plan understood
Balanced-diet and substitute advice received
Any validated tests (coeliac, lactose) arranged
Allergy 'red flag' symptoms understood
Gut 'red flag' symptoms understood
Review appointment booked

⚠ Get urgent help if…

Hives, swelling of the lips, tongue or throat, or breathing difficulty after a food — this suggests allergy; call 999 if breathing is affected
Unintentional weight loss
Blood in your stools or black, tarry stools
Persistent vomiting or difficulty swallowing
A lasting change in bowel habit, especially over the age of 50
Severe or worsening tummy pain

Who to contact: your clinician, clinic or test provider first (keep their number to hand). For urgent advice when you can't reach them, call NHS 111. In an emergency, call 999.

General guidance — it doesn't replace the specific advice your specialist gives you.

Results & realistic expectations

A good result is a clear understanding of whether food is really causing your symptoms, which foods if any, and a balanced plan that eases symptoms without needless restriction. Often the most useful 'result' is a well-kept diary and a supervised reintroduction, not a test number.

The assessment cannot give you a tidy list of 'foods to avoid' from a blood test, because no such reliable test exists. A normal set of validated tests does not mean your symptoms are imagined — it often points to a functional cause such as IBS, which can still be managed.

How long it lasts

Some intolerances, such as lactose intolerance, can change over time and may be partial rather than absolute, so you may tolerate small amounts. An eating plan should be reviewed periodically to make sure it is still needed and still balanced. Avoiding foods indefinitely without review risks unnecessary restriction and nutritional gaps.

Related tests, treatments or support

A food intolerance assessment is often combined with assessment for IBS, coeliac disease and, where the history suggests it, true food allergy. Dietitian input is commonly combined with it to protect nutrition and to run elimination and reintroduction safely.

Follow-up & long-term care

You should be reviewed after a diary or elimination trial to interpret the findings and agree a longer-term plan. Validated test results usually return within a couple of weeks. Ask who to contact if symptoms change, if you lose weight, or if you have any reaction involving swelling or breathing.

Review any restricted diet periodically to check it is still needed
Reintroduce foods you can tolerate to keep your diet varied
Keep nutrition balanced, with substitutes for any removed staples
Re-seek advice if symptoms change or new ones appear
Do not act on unproven 'intolerance' retests

Repeat, follow-on and what comes next

Elimination trials often need repeating or refining to be conclusive.
Tolerance to some foods (such as lactose) can change, so plans are reviewed over time.
If food is not the cause, the focus shifts to managing a condition such as IBS.

Ask what happens if the result is unclear or needs repeating, and what is included if further tests or follow-up are needed.

What good aftercare looks like

A clear, supervised plan with reintroduction and review built in.
Dietitian support to keep your diet balanced.
A named route to seek review if symptoms change.
Clear advice on allergy and gut red-flag symptoms.
Onward referral if another condition is suspected.

What affects the cost

Costs vary a great deal between people and providers, and we don't publish prices. What matters is understanding what drives the cost and making sure your quote is complete. The main things that affect it:

Length and complexity of the consultation
Whether a dietitian is involved and for how many sessions
Validated tests where indicated, such as coeliac blood tests or a lactose breath test
Support during an elimination and reintroduction plan
Follow-up appointments to review and adjust the plan
Whether referral for separate allergy assessment is needed

Make sure your written quote includes

The clinician's or dietitian's fee, and number of sessions included
Which validated tests are included and the cost of any extras
Confirmation that unproven 'intolerance' tests are not part of the package
Cost of follow-up and reintroduction support
What happens, and what it costs, if another condition is suspected
Cancellation policy

On the NHS? Food-related symptoms are assessed on the NHS, including dietitian referral when indicated; private dietitian-led assessment is also common, but reputable services do not rely on unproven 'intolerance' blood tests.

You're entitled to your total cost in writing — including reports, follow-up and what happens if the result is inconclusive — before you decide.

Choosing a specialist safely

Check the specialist is on the GMC Specialist Register for this area.
Make sure they work at a CQC-registered service, and look for membership of the relevant Royal College or professional body.
You're entitled to time to consider and to have your questions answered before you agree — the specialist who looks after you should explain it, not a salesperson.
Be wary of pressure: time-limited offers or deposits taken before you've had time to think are red flags, not bargains.
You're entitled to your total cost in writing — including any follow-up — before you decide.

How Vuemedics verifies every consultant →

Questions to ask your medical professional

Take this to your consultation. A good specialist will welcome every one of these.

Are my symptoms more likely intolerance, allergy, or another condition such as IBS or coeliac disease?
Why are high-street 'intolerance' blood tests not recommended?
How will we actually identify which foods, if any, cause my symptoms?
How do I keep my diet balanced if I cut foods out?
Which validated tests, if any, do I actually need?
What symptoms should make me seek urgent or separate assessment?
Are you on the GMC Specialist Register for this area, and which Royal College or professional body are you a member of?
Will you be the specialist who carries out my test, and who looks after me afterwards?
What are the risks for someone like me, and how often do your own patients have a problem or need it repeated or redone?
What does a realistic result look like — and what can this test not achieve?
What are my options, including waiting, doing nothing for now, or choosing a different approach?
Can I have written information, results and aftercare instructions in a format I can use, including any accessibility or communication support I need?
What is the total cost in writing, including any follow-ups, and how much time do I have to decide?

Frequently asked questions

Should I get a food intolerance blood test?

No. High-street and online 'food intolerance' blood tests, usually measuring IgG, are not recommended by Allergy UK or BSACI. IgG to food is found in healthy people and simply reflects your diet, so the test cannot diagnose intolerance and can lead to needless restriction.

What is the difference between food intolerance and food allergy?

Allergy involves the immune system and can cause sudden, sometimes life-threatening reactions such as swelling or breathing problems. Intolerance is trouble digesting food, causing symptoms like bloating or diarrhoea, and is not life-threatening. They are assessed differently.

How is intolerance actually diagnosed?

Mainly through your history, a food and symptom diary, and a carefully supervised elimination and reintroduction of suspected foods. Validated tests, such as for coeliac disease or lactose intolerance, are used where they fit.

Can I have this assessed on the NHS?

Yes. GPs assess food-related symptoms and can refer to NHS dietitians or specialists where needed. Private dietitian-led assessment is also widely available.

Is it safe to cut out foods while I work this out?

Cutting out major foods without guidance can cause nutritional gaps and can hide conditions like coeliac disease. Do it only under advice, with a plan to reintroduce and review.

What if my tests are all normal?

Normal validated tests do not mean nothing is wrong. Symptoms are often due to a functional cause such as IBS, which can be managed with diet and other measures.

Find a verified specialist for food intolerance assessment

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How we made this page

Medically reviewed by a GMC-registered consultant. Written in plain English, checked against NHS, NICE, GMC and relevant Royal College / specialist-society guidance, and kept under review. No clinic paid to appear on this page, and we publish no pricing. This is general information to help you prepare — it is not a substitute for advice from your own clinician. How we review our guides →

Source hierarchy: UK regulator and NHS/NICE guidance first, then relevant Royal College or specialist-society guidance, then peer-reviewed evidence for procedure-specific figures where available.

Sources & standards: Allergy UK — Food intolerance BSACI — Choosing Wisely: alternative tests in food allergy/intolerance (PDF) British Dietetic Association — Food allergy and intolerance testing NHS — Food intolerance NICE — Food allergy in under 19s (no role for IgG testing)

Reviews reflect patients' experience of care, not clinical outcomes. For procedure volumes and outcome data see PHIN.

Last medically reviewed 2026-09-21. Spotted something wrong or out of date? Report an error in this guide.