Oral ferrous fumarate dosing regimens in peritoneal dialysis: a single-center retrospective audit

Background Anemia is highly prevalent in patients with kidney failure receiving peritoneal dialysis (PD). Oral iron supplementation is frequently prescribed, but adherence may be limited by pill burden and gastrointestinal adverse effects. Emerging evidence suggests that less frequent oral iron dosing may enhance iron absorption by reducing hepcidin-mediated inhibition, yet data in PD patients are lacking. We evaluated iron utilization and compared the effectiveness of different oral iron regimens in PD patients. Methods This retrospective cohort study (2007-2025) included adults (≥18 years) receiving peritoneal dialysis at the Dialysis Center Groningen who were treated with oral ferrous fumarate for ≥3 months. Patients receiving intravenous iron, other iron formulations, non-standard dosing regimens, or with active gastrointestinal bleeding were excluded. Ferrous fumarate regimens included 200 mg once daily (OD), twice daily (BID), three times daily (TID), or three times weekly (TIW). Patients not receiving oral iron were evaluated for treatment eligibility. Primary outcomes were 6-month changes in hemoglobin, ferritin, and transferrin saturation. Regimen-specific trajectories were analyzed using linear mixed-effects models. Sensitivity analyses adjusted for age, sex, erythropoiesis-stimulating agent dose, and inflammation, and were restricted to incident iron users on PD. Results Of the 140 patients screened, 85 patients were included (median age 61 years; 57.6% male). TIW dosing resulted in hemoglobin trajectories comparable to OD dosing (P = 0.30), with similar ferritin and transferrin saturation trajectories. In contrast, BID dosing was associated with a steeper hemoglobin increase (0.013 g/dL/day; P = 0.001) than OD dosing. Sensitivity analyses yielded similar results. Among patients not receiving iron therapy, 30% (n= 9/30) met contemporaneous guideline criteria for treatment. Conclusion In this 18-year retrospective study of 85 PD patients, TIW and OD oral iron supplementation produced comparable hematologic outcomes, suggesting that less frequent dosing may represent an effective strategy to reduce treatment burden without compromising efficacy. Twice-daily dosing was associated with faster hemoglobin increases, likely reflecting greater cumulative iron exposure. Iron therapy was underutilized in a substantial proportion of eligible patients. Although limited by the modest sample size, these findings highlight the need for expert consensus to address evidence gaps and guide anemia management in PD.