The testing for human blood in the stool is the gentlest method of discovering a colon or stomach cancer. The fecal occult (hidden) blood test (FOBT) test is well known.

With this test, three different stool samples are analysed. The disadvantage of this test is that it can show a positive result with animal blood which has been eaten or small amounts of vitamin C from fruit or drinks. This means that the test shows the presence of blood which does not come from the patient. The result can be a colonoscopy or gastroscopy which is not required.

Alternatively a metabolic biomarker screening for colorectal cancer can be carried out (M2-PK in the stool). This new method is able to detect bleeding or non-bleeding bowel cancers, and polyps. It is highly sensitive and specific, and does not depend on hidden blood, but on tumor metabolic activity. No diet is required. There are no false results due to haemorrhoids or other sources of blood in the bowel. And only one small sample is required.