What the test is

Calprotectin is a protein carried by white blood cells. When the lining of the bowel is inflamed, white cells move into the gut and calprotectin passes into the stool, where we can measure it. The result tells us how much inflammation there is in the bowel at that moment. It does not tell your doctor where the inflammation is, and it is not a test for cancer.

Why we use it

Symptoms alone are an unreliable guide in inflammatory bowel disease. People can feel well while the bowel is still inflamed, and people can have troublesome symptoms — from irritable bowel syndrome, bile acid diarrhoea or a healed but scarred bowel — when there is no inflammation at all. Calprotectin separates these two situations, so that treatment is changed when it needs to be and left alone when it does not. It also allows us to follow you between colonoscopies rather than repeating endoscopy, and it often rises weeks before a flare becomes obvious.

How to collect the sample

• Use the first bowel motion of the day, as levels vary through the day.
• Do not pass urine into the container, and take the sample before it touches toilet water — use the collection paper or a clean, dry container.
• Fill the pot to about a third with the spoon in the lid. A small amount is enough.
• Write your name, ID and the date and time on the pot.
• Return it to the laboratory as soon as you can, within three days at the latest, and keep it in the fridge until you do.
• Do not send a sample during an episode of infectious diarrhoea, or while you have heavy rectal bleeding, unless we have asked for it.

What the result means

These are the cut-offs this service uses for monitoring people already known to have inflammatory bowel disease; they are a practical guide rather than a fixed guideline, and different numbers are used when calprotectin is being used to decide whether someone has the disease in the first place. Always read the result alongside your symptoms and your other tests, and let us interpret it with you rather than acting on the number alone.

Things that can raise the result without a flare

A gut infection, anti-inflammatory painkillers such as ibuprofen, diclofenac and aspirin, acid-reducing tablets such as omeprazole, and bowel polyps or coeliac disease can all raise calprotectin. Tell your doctor what you are taking when the sample is sent. Do not stop a prescribed medicine in order to have the test.

Its limits

Calprotectin is much less reliable when Crohn’s disease affects only the small bowel — the result can be normal while the small bowel is actively inflamed. If your disease is in the small bowel we will rely more on MR enterography, intestinal ultrasound or capsule endoscopy. A single result is only a snapshot; the trend over several tests is far more useful than any one number.

How often it is checked

The sample can be handed in and the result reviewed at your local health centre; you do not need to wait for a clinic appointment for that. In settled disease we usually check calprotectin every three to six months, and about three months after starting or changing a treatment. We will also ask for a sample whenever your symptoms change. Please bring your sample pot to each clinic visit, or collect one from us before you leave.

Contact your doctor using the numbers your clinic has given you. If you are seriously unwell, or it is outside working hours, go to the Emergency Department rather than waiting for a reply. Reference ranges differ between laboratories — confirm the range printed on your own report. Version 1.0 · review date October 2028.

This leaflet is general information and does not replace advice from your own doctor.