We recommend that all patients with a subnormal hemoglobin level should have a repeated simple biochemical standard blood test including the measurements of Hb, MCV, eGFR, Ferritin, s-TfR (or se-Fe and TIBC), CRP, B12 and folate, to indicate whether the patients have an explained or unexplained anemia. The gene discussed is CRP; the disease is anemia (phenotype).