FGF23: fibroblast growth factor 23; FDI: ferric derisomaltose, IFX: Infliximab; IDA: iron deficiency anemia; IS: iron sucrose; IBD: inflammatory bowel disease; FCM: ferric carboxymaltose; AE: adverse events; UC: ulcerative colitis; CDAI: Crohn's disease activity index; CRP: C-reactive protein; CD: Crohn’s disease; Hb: hemoglobin; MCV: mean corpuscular volume; TEAE: treatment associated adverse effect; ALT: alanine aminotransferase; TSAT: transferrin saturation; IV: intravenous; SI: sucrosomial iron. Here, GSTM1 is linked to ulcerative colitis.