When subgroup analyses were conducted according to the study types, no associations were detected in cohort group (RR, 1.25; 95% CI, 0.95-1.65; I2, 75.7%); however significant association was detected in case–control group (RR, 2.15; 95% CI, 1.41-3.26; I2, 89.1%).The significant association between insulin use and CRC risk was detected in the studies in America (RR, 1.73; 95% CI, 1.15-2.60; I2 = 67.8%) and Asia (RR, 2.55; 95% CI, 2.14-3.04; I2 = 3.9%). The gene discussed is INS; the disease is colorectal carcinoma.