PMCH and type 2 diabetes mellitus: As shown in Figure 4, genetically predicted MCH, MCHC, RDW, and MCV were significantly associated with decreased risk of T2D using the IVW estimator with an OR of 0.947(CI: 0.913–0.984, P = 0.005), 0.953 (CI: 0.914–0.997, P = 0.035), 0.908(CI: 0.873–0.946, P= <0.001) and 0.774(CI: 0.672–0.890, P= <0.001), respectively.