Should I refer to a patient’s hemoglobin (Hb) or hematocrit (Hct)?

By William Aird

Depends on the clinical context. In patients with anemia, we should refer to the Hb because oxygen carrying capacity is limiting, whereas the Hct should be considered in those with polycythemia since blood viscosity is limiting. For those with normal Hb/Hct, both oxygen carrying capacity and blood viscosity are at equipoise, so take your choice!