Otitis media (OM) is a common infection of the middle ear that often affects young children. Cefdinir, a third-generation cephalosporin, is commonly prescribed to effectively treat OM. However, when Cefdinir is co-administering with iron-containing formulations, it can potentially result in the appearance of bloody-coloured stool. We presented a 10-month-old male infant who was admitted to the emergency after experiencing reddish-coloured stool while on Cefdinir and a multivitamin-containing iron formulation three days prior to the visit. During the physical examination, all vital signs were normal, and blood tests revealed no abnormalities. Upon consultation with a drug information specialist, it was determined that the interaction between Cefdinir and iron was the likely cause, and parents were advised to discontinue the use of the antibiotic agent.