Results: In patients with T2DM with advanced HF, serum FGF21 level was significantly positively correlated with eGFR (ρ = 0.35, p = 0.0125) and triglycerides (ρ = 0.28, p = 0.0465) and significantly negatively correlated with serum levels of HDL cholesterol (ρ = −0.29, p = 0.0386) and with RV-RA gradient (ρ = −0.30, p = 0.0358). This evidence concerns the gene FGF21 and type 2 diabetes mellitus.