A 47 year old woman who is pre-menopausal presents to her GP feeling “tired all the time.” She takes thyroxine for hypothyroidism and asks when a dose increase is indicated. She discloses drinking a bottle of wine daily and reports that her sleep is rarely unbroken. You take a blood sample, and the results show raised ferritin 500 µg/L (normal range 15-300 µg/L), alanine transaminase (ALT) 100 IU/L (1-40 IU/L), and C reactive protein 70 mg/L (0-5 mg/L). Results of other investigations are normal, including full blood count, kidney function, and thyroid function.
Serum ferritin is a commonly requested investigation in primary care.1 Ferritin is an intracellular iron storage protein.2 It can represent total iron stores3 and is most often requested in primary care when investigating anaemia or associated symptoms (fatigue, restless legs, hair loss).1 It is also commonly requested in further investigation of abnormal liver blood results4 or to monitor patients with iron overload.1 Low serum ferritin indicates low iron stores and is usually easy to interpret and manage; however, raised serum ferritin often presents a significant diagnostic challenge owing to multiple possible causes.