Faecal calprotectin: what it is, what it tells you and when it’s tested

Calprotectin is a protein found in white blood cells. When your gut is inflamed, white cells gather there in large numbers and calprotectin ends up in your stool. Measuring it shows whether there is inflammation in your gut.

When it’s tested

Doctors mostly order it for people who have had diarrhoea, tummy pain or bloating for weeks. It helps tell irritable bowel, which does not inflame the gut, from an inflammatory disease such as Crohn’s disease or ulcerative colitis.

People who already have one of these diseases repeat it over time, to see whether the inflammation is under control.

It is not a test for people who feel well and have no symptoms, and it is not a test for bowel cancer. That is why Rosa does not test it. Instead it measures CRP, which shows inflammation in the blood, and the blood count and ferritin, which show anaemia.

What it tells you, and what it does not

If it is low, an inflammatory bowel disease is unlikely. In adults this spares many unnecessary colonoscopies.

If it is high, it says there is inflammation, but not which kind. It can be an inflammatory disease, an infection, the effect of a medicine or, sometimes, a polyp.

It does not replace a colonoscopy when a doctor suspects cancer. In that case a normal result is not enough to reassure.

That is why it is read together with other tests:

Normal faecal calprotectin levels

The lab decides what is normal, and it varies a little from one kit to another. Many labs treat a value below 50 µg/g as normal. The range on your own report is what counts.

A value just above the limit is not enough for a diagnosis. Your doctor often repeats the test after a few weeks, if possible without anti-inflammatories in the days before: your doctor decides.

In young children the values are read differently: the paediatrician interprets them.

What your result means

Find the row for your result, in µg/g. If it is 50 or above, talk to your doctor.

If your calprotectin is high or low

Why calprotectin is high

These are the most common causes. Other tests are often needed to tell which.

What can skew the result

A few things raise it even without a bowel disease. It helps to tell your doctor.

When to worry

Talk to your doctor if:

Frequently asked questions

What are normal faecal calprotectin levels? Many labs treat a value below 50 µg/g as normal. The limit varies a little between kits: the range on your own report is what counts.

What does high calprotectin mean? That there is inflammation in your gut. It can be an inflammatory disease, an infection or the effect of a medicine. Your doctor decides whether to repeat the test or do others.

Can calprotectin tell IBS from Crohn’s disease? It helps a lot. Irritable bowel does not inflame the gut, so calprotectin usually stays low. In Crohn’s disease and ulcerative colitis it is usually high. The diagnosis is still your doctor’s, sometimes with a colonoscopy.

How do I collect the stool sample? The pharmacy or lab gives you a container with a small scoop. A small amount is enough. Follow the lab’s instructions on how to store it and when to drop it off.

Does Rosa test faecal calprotectin? No. It is not a blood test, and people who feel well do not need it. Rosa measures CRP, haemoglobin and ferritin, which show whether there is inflammation or anaemia. If your doctor wants calprotectin, they order it separately.

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