The best blood test to detect iron deficiency

Dr Mark Crowther is a professor and chair of the Department of Medicine and the Leo Pharma Chair in Thromboembolism Research at McMaster University.

What is the best blood test to check if a patient has iron deficiency?

Mark Crowther, MD, MSc: The best blood test to check if a patient has iron deficiency is a ferritin. In the vast majority of patients, a ferritin is a very reliable indicator. A ferritin that is less than the lower limit of the reference interval in your lab is a reliable predictor of iron deficiency. There is nothing else that causes a low ferritin. A normal ferritin in a patient who has no inflammatory state is a reliable exclusionary criterion for the presence of iron deficiency.

The only really confusing state is when a patient has a systemic inflammatory state or liver disease, in which case it becomes much more complicated.