The aim of the study is to investigate if iv iron formulation improve recovery after surgery with blood loss. Post-operative anaemia is a common debilitating condition after major surgery due to a combination of preoperative iron deficiency anaemia (IDA) and per-operative blood loss. Median blood loss following hepatopancreatobiliary (HPB) and complex aortic surgery typically range between 500-1000 ml. Bioavailability of iron may be a rate limiting factor in erythropoiesis in anaemia secondary to blood loss. For the IRIS trial, it is hypothesized that intravenously (iv) administered Ferric Carboxymaltose after a per-operative blood loss of 400-4000 ml, improves post-operative recovery and reduces the RBC transfusion. Patients scheduled for elective HPB surgery or complex aortic surgery will be screened for eligibility and recruited into the study. By the end of the surgical procedure, if blood loss is estimated to 400-4000 ml, the patient is randomized 1:1 to iv 1000 mg Ferric Carboxymaltose or placebo. The primary endpoint is a composite of death, number of RBC transfusions, post-operative severe anemia (Hb \<80 g/L) and FACT-An Quality of life (QoL) five weeks after surgery, assessed by win ratio. The trial will also examine effects on; a) levels of Hb; b) markers of erythropoiesis and iron bioavailability; c) post-operative complications; d) post-operative recovery; e) performance status; f) subgroups based on type of surgery and degree of anemia and iron deficiency; g) re-admissions; h) long term outcome based on patient medical records and i) how post-operative recovery differs between those with low (\<400 ml), high (400-4000 ml) and very high (\>4000 ml) per-operative blood loss. Recruitment will continue until 338 patients are randomized or 304 have completed the five week follow up The coordinating center of the trial is the Department of Surgery at Uppsala University Hospital. Participating sites are also Linköping University Hospital and Lund University Hospital, all in Sweden. Other sites may be added.