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Análisis Médicos

Digestive and intolerance tests

The digestive tests in this category use blood, exhaled breath or stool, depending on the question. Coeliac disease is first investigated with antibodies, intolerances and SIBO with breath tests, and the gut microbiota with a stool sample.

At Análisis Médicos we have kept each test separate so that tests which are prepared and interpreted differently are not confused. The Helicobacter pylori test is also a breath test, but it uses labelled urea and shows whether there is an active infection; it is not a sugar fermentation test.

Digestive tests available

If you are not sure which one suits you, there is a guide below the list to help you choose.

How it works

You can order our digestive and intolerance tests yourself, and almost all of them without your doctor having to request them:

Price
From €60.00
Prescription
Depends on the test
Appointment
Depends on the test
Results
3 to 15 working days
  • Your test request, in minutes. Order the profile you want and it arrives in your inbox straight away, with the preparation instructions.
  • Wherever suits you. You can have your test at any of the 45 partner centres, and the laboratory emails you the results within a few days. Tests that need an appointment say so on their page.
  • With an invoice. When you order, you receive an invoice you can submit if you have reimbursement health insurance. How it works, step by step.

How to choose your digestive test

This is not medical advice and does not replace a consultation: it is the reasoning I would use to choose, in case it helps you decide which one to order.

For a first assessment of coeliac disease while you are still eating gluten, the antibody blood test is the usual starting point. The HLA genetic test is kept for specific situations, such as conflicting results or a gluten-free diet that has already been started. A genetic predisposition does not confirm the disease.

To investigate malabsorption of a sugar, there are separate tests for lactose, fructose and sorbitol. The SIBO test answers a different question, even though the procedure and some symptoms may look similar.

**To look for active Helicobacter pylori infection**, the C13 urea breath test is used both for the initial assessment and to check eradication after treatment.

To investigate vitamin B12, the initial blood test brings together B12 and related markers. The profile with antibodies looks for a possible autoimmune cause. Methylmalonic acid is a complementary test for borderline results, not a general first-line test.

The gut microbiota test describes the composition of the stool sample. It is a secondary test that requires a specific clinical question, and on its own it does not diagnose the cause of digestive symptoms.

Dr. Antonio Mas

Blood, breath and stool answer different questions

Coeliac antibodies are measured in blood and are only reliable if you are eating gluten. Genetics do not change with diet, but a compatible variant indicates predisposition, not active disease.

The lactose, fructose, sorbitol and SIBO tests measure hydrogen and, depending on the protocol, methane in exhaled breath after a sugar load. The Helicobacter pylori test also analyses breath, although its mechanism is different: it uses labelled urea to show activity of the bacterium.

The microbiota test works with a stool sample. It describes microorganisms and estimated functions, but current knowledge does not yet allow each difference to be turned into an individual diagnosis or treatment.

Preparation is part of the test

In breath tests, antibiotics, laxatives, prokinetics, stomach protectors and the preceding diet can change the result. The restrictions are not the same for every test, so follow the page for the test you have ordered.

With coeliac disease the opposite of what many people expect happens: cutting out gluten before the antibodies are measured can make the result unreliable. If you have already cut it out, do not reintroduce it on your own in order to have a test.

Symptoms are not a safe way to choose

Bloating, wind, pain and changes in bowel habit appear in different conditions. Similar symptoms do not turn a lactose test into a SIBO test, nor do they make it possible to decide automatically which one applies. When there is no defined question, a clinical assessment is required before ordering a targeted test.

Before the test

Coeliac disease: no fasting is required, but you must keep eating gluten as normal. If you already follow a gluten-free diet, seek advice before the blood test.

Vitamin B12: the B12 profiles require 8 to 12 hours of fasting. Methylmalonic acid on its own does not require fasting. Mention any supplements and do not stop them on your own.

Breath tests: these require an appointment. The lactose, fructose, sorbitol and SIBO tests last between 2 and 3 hours and require 12 hours of fasting, as well as the preparation diet set by the centre. The Helicobacter pylori test lasts about 30 minutes and requires at least 6 hours of fasting. Check each test page for the time limits on antibiotics and other medicines.

Microbiota: no fasting or appointment is required. The stool sample is collected at home with the kit and must be stored and handed in according to the centre's instructions.

Frequently asked questions

Which test is used first to investigate coeliac disease?
The usual starting point is blood antibodies while you are still eating gluten. Genetic testing is kept for specific situations, and a genetic predisposition does not confirm the disease.
Are the intolerance tests and the SIBO test the same?
They share the analysis of exhaled breath, but they use different sugar loads and criteria. Each one answers a different question.
Do all breath tests take the same time?
No. The lactose, fructose, sorbitol and SIBO tests last between 2 and 3 hours. The Helicobacter pylori test lasts about 30 minutes.
Should I stop eating gluten before a coeliac blood test?
No. Cutting it out can lower the antibodies and make the result unreliable. If you already follow a gluten-free diet, seek advice before having the test.
Does the microbiota test diagnose the cause of my symptoms?
Not on its own. It describes the stool sample, but its findings must be assessed with a specific clinical question and do not automatically lead to a treatment.

If you already have your results

A figure only makes sense in its context. Medical history, symptoms, medication and the conditions of the sample can change what it means. Results are assessed in a consultation; this page is for comparing and ordering profiles.

The laboratory sends you the results directly. You can then review them with the professional of your choice.

For breath and stool tests, always check the test page, because the preparation is specific.

See digestive and intolerance tests

Guide reviewed by Dr. Antonio Mas, specialist in Endocrinology and Nutrition, Spanish medical licence no. 080846289, in September 2026.

And if you were looking for something else, here are all the blood tests in the catalogue, grouped by topic.