The primary aim of this clinical trial is to investigate the effects of intravenous iron on recovery in mobility compared to the pre-fracture level in patients with a hip fracture The main questions it aims to answer are: It is hypothesize that intravenous iron will enhance gains in mobility and hereby recovery of mobility, increase hemoglobin (Hgb), lower fatigue, have a positive effect on skeletal muscles in the weeks and months after administration. The primary objective is to compare the effect of a single dose of ferric derisomaltose (FDI) (20 mg/kg body weight) relative to placebo on patients' recovery of functional mobility, measured as the change from baseline in the New Mobility Score. Participants will: \- Receive either a single dose of intravenous FDI (20 mg/kg body weight) (and saline) or placebo (saline) at 1-5 days after surgery. This trial will be conducted at three hospitals in Denmark, involving an anticipated 210 participants.