High doses of supplemental iron (45 mg / day or more) may cause gastrointestinal side effects, such as nausea and constipation [5]. (ods.od.nih.gov)
Your baby probably doesn't need to take supplemental iron drops — at least not for the first four months. (babycenter.com)
Yet increased intakes of vitamins A and B6 may be required to resolve the anemia, with or without supplemental iron depending on need. (westonaprice.org)