This test is done as a routine work-up to diagnose type and degree of anemia. There are Several factors which could be responsible for low Hemoglobin level like age, sex, pregnancy etc.The hemoglobin test may be used to screen for, diagnose, or monitor a number of conditions and diseases that affect red blood cells (RBCs) and/or the amount of hemoglobin in blood. It is often used with a hematocrit as a quick evaluation of the number of RBCs or is performed as part of a complete blood count (CBC) as an integral part of a health evaluation.