Given the clinical relevance of glycemic control, Spearman’s rank correlation analysis was conducted to assess the relationship between glycated hemoglobin (HbA1c) levels and concentrations of selected fibroblast growth factors (FGF-2, FGF-19, FGF-22, and FGF-23) in patients with diabetes (n = 73). The gene discussed is FGF23; the disease is diabetes mellitus.