Awareness of iron deficiency and its early manifestations has grown in recent years. Although oral iron remains first-line therapy, many patients fail to tolerate or adequately respond to it, leading to broader use of intravenous iron isomaltoside in primary care settings. While IV iron is generally safe, both pseudoallergic and true allergic hypersensitivity reactions can occur. Early recognition and timely management are critical to ensuring patient safety.Clinical data for this case report were obtained from a 29-year-old otherwise healthy woman who developed a hypersensitivity reaction during an intravenous iron isomaltoside infusion. Data were collected through direct observation and continuous monitoring of vital signs during the infusion and for 1.5 hours thereafter. Additional information was retrieved from electronic medical records and from a follow-up assessment after treatment. The infusion protocol, onset and progression of symptoms, and all therapeutic interventions—including administration of corticosteroids and antihistamines—were documented in chronological order. Written informed consent for infusion and publication was obtained from the patient.The case presents real-time management of hypersensitivity reactions to iron isomaltoside infusion.Hypersensitivity reactions to intravenous iron can occur even in young patients without prior allergy history. Immediate recognition, stepwise management, and close monitoring are essential for preventing complications.Pseudoallergic hypersensitivity reactions to intravenous iron may present with subtle early symptoms such as head heaviness or mild pruritus before progressing to more pronounced manifestations. In this case, a rapid escalation from mild to objective symptoms (urticaria) underscores the importance of early recognition. The lack of response to dexamethasone alone and immediate improvement after clemastine supports existing guidance that antihistamines are central in the management of pseudoallergic IV iron reactions, whereas corticosteroids may play only an adjunctive role. Consistent, structured monitoring during and after infusion allowed early detection, timely intervention, and prevention of more severe complications.Even early and seemingly mild symptoms during IV iron infusion may precede a clinically significant hypersensitivity reaction. Prompt, stepwise management with antihistamines and corticosteroids—combined with vigilant monitoring—is essential for safe and effective care.