An inquiry-based mole-to-mass activity is presented associated with the analysis of blood. Students working in groups choose between two medical cases to determine if the "patient" has higher or lower concentrations of minerals than normal. The data are presented such that students must convert moles to mass in order to compare the patient values to known values from literature sources. The activity is flexible for adaptation to one or two class periods depending on the length of time in a specific school's schedule. (Contains 1 table.)