In addition to colorectal cancer (odds ratio(OR), 9.27 (95% confidence interval (CI): 3.61–23.83; p< 0.001)), older age (OR, 1.52 (95% CI: 1.00–2.32; p =0.05)), deprivation (OR, 1.54 (95% CI: 1.21–1.94; p <0.001)), oral anticoagulants (OR, 1.78 (95% CI: 1.01–3.15;p = 0.046)), rectal bleeding (OR, 1.47 (95% CI:1.15–1.88; p = 0.002)), advanced adenoma (OR, 7.52 (95% CI:3.90–14.49; p < 0.001)), non-advanced polyps (OR, 1.78(95% CI: 1.33–2.38; p < 0.001)) and inflammatory boweldisease (IBD) (OR, 4.19 (95% CI: 2.17–8.07; p < 0.001))independently predicted raised f-Hb. This evidence concerns the gene GSTM1 and colorectal cancer.