The goal of this clinical trial is to find out which method is better for guiding iron treatment in adult patients with end-stage kidney disease (ESKD) on hemodialysis who have anemia. The main questions it aims to answer are: Can using reticulocyte hemoglobin equivalent (RET-He) to guide intravenous (IV) iron treatment be as effective as using transferrin saturation (TSAT)? Does the method used to guide iron treatment affect outcomes such as death, heart problems, hospitalizations, infections, or the need for blood transfusions? Researchers will compare RET-He-guided iron treatment with TSAT-guided iron treatment to see if RET-He works just as well and has similar or better outcomes. Participants will: Receive IV iron based on either RET-He or TSAT levels Have blood tests done at the start, 3 months, and 6 months Have their doses of iron and erythropoietin (a medication to treat anemia) adjusted based on the assigned protocol Be monitored for clinical outcomes such as hospitalization, heart events, and infections