Men with more than 1 year's duration of T2DM had a decreased risk of prostate cancer compared to men without T2DM (HR = 0.85, 95% CI = 0.82–0.88) but among men with T2DM, those on metformin had no decrease (HR = 0.96, 95% CI = 0.77–1.19), whereas men on insulin (89%) or sulfonylurea (11%) had a decreased risk (HR = 0.73, 95% CI = 0.55–0.98), compared to men with T2DM not on anti‐diabetic drugs. This evidence concerns the gene INS and Familial prostate cancer.