The addition of a normal haemoglobin concentration from a full blood count to a f-Hb < 10 μg/g was able to effectively exclude colorectal cancer in 99.96% of cases, providing excellent reassurance to GP’s and to specialist practitioners who must prioritise access to endoscopy services, particularly in the context of the current COVID pandemic and recovery period. Here, GSTM1 is linked to colorectal cancer.