IBS vs food intolerance: what is the difference?

General information, not health advice. Talk to your doctor or dietitian about your own symptoms.

They can feel the same. They are not the same thing, and a doctor is the one who sorts it out.

Last updated 2026-10-31 · By Torstein Skulbru

The short version

Both can cause bloating, cramps and trips to the bathroom, and both can be set off by food. They are different things. You cannot tell them apart from how they feel, and a guide or an app cannot tell you which one you have. A doctor can.

Side by side

IBS (irritable bowel syndrome)

A common condition that affects the digestive system. The NHS describes it as usually lifelong, although lifestyle changes and medicine can help.
Main symptoms: stomach pain or cramps, bloating, diarrhea, constipation.
Symptoms come and go, with better days and worse days (flare-ups). Food and drink can be a trigger, and so can alcohol, caffeine, stress and antibiotics. Flare-ups can also happen for no obvious reason.
There is no single test for it. A GP asks about your symptoms and may arrange tests to rule out other causes.

Food intolerance

Difficulty digesting certain foods or ingredients. The NHS says it is not usually serious, but it can make you feel unwell.
Symptoms usually start a few hours after eating the food: bloating, diarrhea, gas and tummy pain are common.
The most common one is lactose intolerance (difficulty digesting the sugar in milk and dairy).
It is not caused by the immune system, so it is not an allergy and cannot cause a serious allergic reaction.

Not the same as a food allergy

Sudden swelling of the lips, mouth or throat, trouble breathing, or feeling faint after eating can be a serious allergic reaction. That is an emergency: call your local emergency number.

Where they overlap

Bloating, tummy pain and diarrhea show up in both, and in many other things. Someone with IBS can also have a food that reliably bothers them. That overlap is why guessing from symptoms does not work.

How a doctor sorts it out

They ask what symptoms you have, how often, how long, and whether they come after certain foods.
For IBS, they may arrange a blood test to check for problems like coeliac disease and a poo sample to check for infection and inflammatory bowel disease.
For a food intolerance, they may refer you to a dietitian. Tests can include avoiding a food for a few weeks and then eating it again, a breath test for lactose, and a food and symptoms diary.

The NHS does not recommend some tests you can buy that claim to identify food intolerances: there is limited evidence that they give accurate results, and they may suggest you avoid several foods, which can be harmful.

What the NHS says around an appointment

For IBS, the NHS says writing down details of your symptoms beforehand might help you remember them.
A food and symptoms diary is also used to help work out what may be triggering symptoms.
The NHS says foods should not be cut out of your diet without the advice of a GP or dietitian, because you could miss out on vitamins and minerals.
The NHS says to ask for an urgent appointment if you have bleeding from your bottom, have lost a lot of weight for no reason, or find a hard lump or swelling in your tummy.

Sources

NHS: Irritable bowel syndrome (IBS). IBS is a common condition of the digestive system that can cause cramps, bloating and diarrhoea.
NHS: Symptoms of IBS. Main symptoms, common triggers, and when to see a GP.
NHS: Getting diagnosed with IBS. There is no test for IBS; tests may be used to rule out other causes.
NHS: Food intolerance. What a food intolerance is, how it differs from an allergy, and why some home tests are not recommended.

Gutrude is a tracker, not health advice: a record you can bring to your doctor or dietitian.