Onmultivariate analysis, older age (≥ 75 years: OR, 1.52 (95% CI: 1.00–2.32;p = 0.050)), deprivation (SIMD 12: 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)), colorectal cancer (OR, 9.27 (95% CI:3.61–23.83; p < 0.001)), 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 bowel disease(OR, 4.19 (95% CI: 2.17–8.07; p < 0.001)) retainedsignificance as independent predictors of a raised f-Hb. This evidence concerns the gene GSTM1 and colorectal cancer.