In this first comparative trial reflecting real-world conditions in patients with quiescent or mild to moderate IBD and mild to severe IDA, both oral ferric maltol and standard regimens of IV ferric carboxymaltose achieved clinically meaningful increases in Hb over 12 weeks of treatment, although ferric maltol did not meet the prespecified noninferiority margin vs IV iron. Here, GSTM1 is linked to inflammatory bowel disease.