Background Ferritin levels serve as an essential marker for iron status and aid in diagnosing iron deficiency anemia. However, ferritin is also an acute-phase reactant and is often elevated in inflammatory conditions. Hyperferritinemia refers to markedly elevated ferritin levels over 10,000 μg/L and is associated with various disorders, including multisystem inflammatory syndrome in children (MIS-C), macrophage activation syndrome (MAS), adult-onset Still’s disease (AOSD), and hemophagocytic lymphohistiocytosis (HLH). These disorders are often difficult to diagnose, leading to life-threatening outcomes. There is growing interest in investigating ferritin as a biomarker for diseases. Ferritin is commonly included in patients’ initial workups, yet its results are underutilized due to seemingly complex clinical interpretations. Case Presentation Here, we present two case reports illustrating the utilization of ferritin in two rare disorders: AOSD and HLH. The first case follows a 37-year-old male presenting with a pruritic rash, flu-like symptoms, joint pain, fever, and chills. After multiple emergency department (ED) visits, the patient was found to have hyperferritinemia to 88,000 μg/L and met the Yamaguchi criteria for AOSD. He was treated with pulse- dose steroids, resulting in a swift resolution of symptoms. The second case follows a 50-year-old female presenting with sepsis secondary to recurrent axillary skin infections. Her complicated hospital course prompted her transfer to the intensive care unit (ICU), and her labs were significant for hyperferritinemia to 39,671 μg/L, which was essential to differentiate between rheumatological and hematological etiologies. She was diagnosed with diffuse large B-cell lymphoma and, unfortunately, passed away. Discussion Recognizing the role of hyperferritinemia is crucial in assessing mortality risk in these diseases. The etiologies of marked hyperferritinemia are complex and often unclear, necessitating consideration of HLH and MAS in critically ill patients with elevated ferritin levels. Hematological malignancies, which may trigger HLH, highlight the need to differentiate these life-threatening conditions. Further research is needed to aid in the effective diagnosis and management of hyperferritinemia-associated disorders, as prompt diagnoses are critical in improving patient outcomes.