Hemoglobin is an iron-containing protein in your blood, which is necessary to transport oxygen to all of your body's organs and tissues. To assess the amount of functional iron in your body, your doctor may measure the concentration of hemoglobin in your red blood cells to find out if it's lower than it should be.1
Non-pregnant women are considered anemic if their hemoglobin levels are below 12 g/dL. Pregnant women are considered anemic if they have less than 11 g/dL. Low hemoglobin levels make it harder for your blood to carry oxygen to all the parts of your body that need it. This can lead to a variety of symptoms associated with iron deficiency anemia.
While hemoglobin concentration can indicate whether you are anemic, it does not determine the cause of anemia. In order for your doctor to differentiate iron deficiency anemia from other types of anemia, he or she will likely need to perform other tests, such as ferritin concentration.1
1 Centers for Disease Control and Prevention. Recommendations to prevent and control iron deficiency in the United States. MMWR Recomm Rep. 1998;47(RR-3):1-36. http://www.cdc.gov/MMWR/preview/mmwrhtml/00051880.htm. Accessed April 9, 2008.