FOBT: Faecal Occult Blood Test & Results Explained


Last updated: 13 December 2017

What is a faecal occult blood test?

A faecal occult blood (FOBT) is a simple bedside test which can also be performed in the laboratory. It uses a colour-change indicator to detect small (‘occult’) amounts of blood in the stools (faeces).

How is a FOBT performed?

An FOBT can be performed in a laboratory, or as a ‘side-room’” test in the hospital or doctor’s rooms.

It involves placing a small amount of stool in contact with a small tablet, with a drop of water.

If the tablet changes colour (usually to blue) it indicates a strong possibility of microscopic amounts of blood being present in the stool.

When would you need an FOBT?

An FOBT may be requested by your doctor if there is a suspicion of bleeding from the gastrointestinal tract.

Small amounts of blood loss that are not visible in the stools can be detected by this test.

FOBTs are often performed in the setting of anaemia (low haemoglobin or blood count), especially if this is due to iron deficiency, it may point to chronic (i.e., over a long period of time) blood loss from the stomach or bowel.

FOBT results explained

FOBTs may be reported as either negative, positive or false positive.


A negative FOBT result means there is no blood in the stool, or normal.


A positive FOBT result means blood present in the stool. This caused by any condition that causes bleeding from the stomach, small intestine, or colon, as well as swallowed blood, for example from a nosebleed (epistaxis).

Typical examples include an ulcer in the stomach or duodenum, inflammation anywhere along the gastrointestinal tract, or even a tumour of the colon or rectum.

False positive

A false positive FOBT result can be due to eating red meat or certain raw fruits and vegetables in the 48 hours prior to the test.

Related specialists

Related procedures

Related tests

Also known as

  • Occult blood – faeces



A: Use HealthEngine to find and book your next GP appointment. Click on the following locations to find a GP clinic in your state or territory.


This article is for informational purposes only and should not be taken as medical advice. If in doubt, HealthEngine recommends consulting with a registered health practitioner.