Over the last years, incretin receptor agonists-including glucagon-like peptide-1 (GLP-1) receptor agonists (GLP-1 RA) and the dual glucose-dependent insulinotropic polypeptide (GIP)/GLP-1 receptor agonist tirzepatide-have dramatically improved the management of type 2 diabetes, overweight and obesity. However, as the use of incretin receptor agonists continues to increase worldwide, micronutrient deficiencies-including iron deficiency-have emerged as newly recognized adverse effects of these drugs. The present article aims to discuss recent preliminary observational evidence on the potential relationship between incretin receptor agonist-based therapies and the development of iron deficiency and iron deficiency anemia (IDA), as well as the potential mechanisms by which incretin receptor agonists may affect iron homeostasis. Potential mechanisms and factors underlying the development of iron deficiency and IDA in patients treated with incretin receptor agonist-based therapies include inadequate dietary iron intake (due to incretin receptor agonist-mediated reduction in food intake and/or gastrointestinal adverse effects of incretin receptor agonists), low dietary variety, monotonous diets, and changes in food preferences, as well as impairment of intestinal iron absorption (due to delayed gastric emptying, reduced small intestinal motility and/or decreased gastric acid secretion caused by incretin receptor agonists). Moreover, vitamin B2 (riboflavin) deficiency and changes in gut microbiota composition are hypothetical mechanisms that may partly explain iron deficiency in patients treated with incretin receptor agonists, although these hypotheses require confirmation through mechanistic studies. Even though iron deficiency and IDA currently appear to be uncommon adverse effects of incretin receptor agonist-based therapies, clinicians should be aware of the possibility of their occurrence to ensure appropriate prevention and management of these nutritional complications. Nevertheless, future prospective studies are certainly needed to better establish the causal relationship between the initiation of incretin receptor agonist-based therapies and the development of iron deficiency/IDA, as well as the exact mechanisms underlying the potential development of these nutritional complications in patients treated with incretin receptor agonists. Meanwhile, the prescription of incretin receptor agonists should not be unjustifiably restricted by the possible and modest risk of iron deficiency and IDA in patients with one or more approved indications for therapeutic use of these agents. Since no established guidelines currently exist for the prevention and management of iron deficiency and IDA in patients treated with incretin receptor agonists, we herein propose practical strategies to address these possible nutritional complications of incretin receptor agonist-based therapies. These proposed strategies should only be regarded as practical clinical approaches deriving from the existing recommendations for the prevention and management of iron deficiency and IDA, although their cost-effectiveness for the prevention and management of incretin receptor agonist-associated iron deficiency/IDA should be appropriately assessed in future clinical trials.
