Background: Osteoblasts, the cells that make up bone, produce and secrete fibroblast growth factor 23 (FGF23). People with chronic renal disease had a higher-than-normal levels of FGF23 in their blood. Objective: The goal of this study was to examine FGF23's possible predictive function for renal impairment (RI) in patients with multiple myeloma (MM). Patients and Methods: Intact FGF23 serum levels were measured in four groups of patients: 1^st Group: 20 MM patients with RI either on dialysis or not; 2^nd Group: 20 MM patients without RI; 3^rd Group: 30 healthy individuals; 4^th Group: 10 RI patients without MM. Results In this study, we found that both MM patients with and without RI had elevated levels of FGF23 (mean=158.50 and 94.75, respectively) than in healthy individuals (mean=25.17). The difference in results between the MM and healthy individual groups was highly significant (p < 0.01). Patients with MM and RI have greater serum iFGF23 levels compared to those with MM and no RI (p < 0.05). Significant direct link exists between iFGF23 and creatinine (p < 0.01), (r=0.689). There is a strong inverse correlation between eGFR and iFGF23 in the serum (p < 0.01). Conclusion: FGF23 levels increase significantly in MM with RI patients and are higher in MM patients with RI than those without RI. Renal impairment in MM may be diagnosed and predicted with the help of FGF23.