TF and chronic kidney disease: In non-dialysis-dependent CKD, absolute and functional iron deficiencies were associated with increased risk of cardiovascular hospitalization, when absolute iron deficiency was defined as transferrin saturation < 20% and/or ferritin < 100 ng/mL and functional iron deficiency as transferrin saturation and ferritin levels of < 20% and 100–500 ng/mL, respectively [14].