Randomized controlled trials with an intravenous iron comparator arm/group included in the meta-analysis.

Six out of the 23 studies contained a co-intervention in both arms as indicated.
Abbreviations: M, male; F, female; CKD, chronic kidney disease; IBD, inflammatory bowel disease; NR, not reported or unclear; GISEs, gastrointestinal side effects shown as percentage of patients that experience gastrointestinal side-effects; Hb, hemoglobin;FeSO4, ferrous sulfate group; IV, intravenous iron group; slow-Fe, modified-release ferrous sulfate.
(1) Iron dose in the FeSO4 group, unless indicated all trials used standard ferrous sulfate (i.e. not modified-release) and daily posology. Tardyferon® used in studies [56,57,61] and Ferrogradumet-Abbot used in study [58].
(2) There was no statistically significant difference in baseline hemoglobin between the ferrous sulfate and the IV iron arms/groups.
(3) Co-intervention: recombinant erythropoietin.
(4) Co-intervention: mebendazole and folic acid.
(5) Co-intervention: vitamin B12 and folic acid.
(6) Co-intervention: folic acid.
Randomized controlled trials with an intravenous iron comparator arm/group included in the meta-analysis.