Interpreting iron studies.

A 63 year old woman visits her doctor with a three month history of fatigue and generalised joint pains. Her medical history is unremarkable and she reports no recent stress, infection, or weight loss. There are no abnormalities on clinical examination. Haemoglobin, creatinine, and electrolytes, liver enzymes, glucose, inflammatory markers, and thyroid function tests are normal. Ferritin, iron, transferrin, and transferrin saturation are also requested. This article discusses some situations in which ferritin and iron studies might be helpful and how to avoid common pitfalls in their interpretation. What are the next investigations?