In a study by Alshayeb et al. [3], treatment with 10,000 IU of vitamin D3 weekly over 8 weeks lead to a significant increase in FGF23 concentrations in subjects without chronic kidney disease (CKD) (n = 25; eGFR > 60 mL/min/1.73 m2). Here, FGF23 is linked to chronic kidney disease.