Abstract Background In the IRONMAN trial, patients with heart failure (HF), a reduced ejection fraction and iron deficiency who were randomly assigned to ferric derisomaltose (FDI), rather than usual care, had a lower rate of the composite of hospitalization for heart failure (HHF) and cardiovascular (CV) death (rate ratio, RR, 0.82; 95% CI 0.66 to 1.02; p=0.07). A COVID-19 sensitivity analysis, censoring data at 1 year of follow-up showed a greater magnitude of treatment effect (RR 0.66; 95% CI 0.48 to 0.91; p=0.011). Purpose Patient-level data from IRONMAN were used to evaluate the effectiveness and cost-utility of FDI compared to usual care for patients with a current or recent HHF, or raised plasma natriuretic peptide concentrations, from a UK National Health Service (NHS) perspective. Methods A cost-utility analysis (CUA) was conducted covering the first year after randomization. Numbers-needed-to-treat (NNTs) were calculated for the primary endpoint censored at 1 year. In the CUA model, patient survival and rates of (re)hospitalization due to HF, other CV events, infections, respiratory conditions, and other non-CV events were modeled based directly on data from the IRONMAN RCT. UK-specific costs were obtained from the national schedule of NHS costs. Quality of life was estimated based on EQ-5D-5L data collected from patients included in the IRONMAN RCT. Results were undiscounted and reported as absolute and incremental costs in 2023 pounds sterling, and quality-adjusted life expectancy in quality-adjusted life years (QALYs). A willingness-to-pay threshold of £20,000 per QALY was adopted to allow calculation of a net monetary benefit (NMB), a summary measure of the overall value of FDI in monetary terms, capturing changes in both cost and QALY outcomes. Results The NNT analysis showed that 9 patients would need to be treated with FDI to avoid one composite primary endpoint event (CV death and HHF) over 1 year. Relative to usual care, FDI was associated with an improvement of 0.01 QALYs per patient over 1 year (0.58 versus 0.57 QALYs). Total average costs per-patient were £1,672 for FDI, versus £1,975 for usual care, leading to a saving of £302 per patient with FDI. The cost of iron procurement was more than offset by reductions in costs of (re)hospitalizations (Figure). FDI was therefore dominant over usual care, yielding an NMB of £483 over 1 year. Conclusions This short-term, within-trial CUA suggests that FDI both improves QALYs and reduces healthcare expenditure versus usual care when administered to patients with HF and iron deficiency in the UK. Iron repletion with FDI may be a prudent allocation of healthcare resources in this patient population.Breakdown of costs