what is a hemoglobin test done for
(For more, see the What is being tested? section.) A hemoglobin test may be used to: Screen for, diagnose, and measure the severity of anemia (low RBCs, hemoglobin and hematocrit) or polycythemia (high RBCs, hemoglobin and hematocrit) Monitor the response to treatment of anemia or polycythemia.