The present disclosure relates to methods and kits for evaluating and/or monitoring a treatment program, such as in an anemic subject or in a subject receiving treatment for anemia, including determining a presence or an amount of growth differentiation factor 15 (GDF15) and/or hepcidin in a biological sample from the subject. Further, in some embodiments, the disclosure provides methods and/or kits for treating a disorder of iron homeostasis in a subject, comprising measuring an amount of GDF15 and/or an amount of hepcidin in a sample from a subject and administering iron and/or erythropoietin (EPO) to the subject if there is a measurable difference in the amount of GDF15 and/or hepcidin in the sample as compared to a reference amount.
