Hemoglobin - the main component of erythrocytes, is a complex protein, consisting of heme and globin. The main function of hemoglobin is to transfer oxygen from the lungs to tissues, as well as to remove carbon dioxide from the body and regulate CBS. In the blood, hemoglobin is predominantly in the form of oxyhemoglobin (this is a compound of hemoglobin with oxygen) and the form of reduced hemoglobin (this is oxyhemoglobin, which gave oxygen to tissues). Oxyhemoglobin is mainly contained in the arterial blood and gives it a bright scarlet color. In venous blood, there is one or another form of hemoglobin, so the venous blood has a dark cherry color.
Determination of the hemoglobin concentration in the blood plays a crucial role in the diagnosis of anemia. The conclusion about the presence of anemia is based on the results of determining the concentration of hemoglobin and the hematocrit in the blood: for men, a decrease in the hemoglobin concentration below 140 g / l and a hematocrit less than 42%; for women - less than 120 g / l and 37% respectively. In anemia, the hemoglobin concentration varies widely and depends on its shape and severity. In iron deficiency anemia in most patients, the decrease in hemoglobin is relatively moderate (up to 85-114 g / l), less pronounced (up to 60-84 g / l). A significant decrease in the concentration of hemoglobin in the blood (up to 50-85 g / l) is typical for acute blood loss, hypoplastic anemia, hemolytic anemia after hemolytic crisis, vitamin B 12-deficit anemia. Concentration of hemoglobin 30-40 g / l - an indicator of severe anemia, which requires urgent measures. The minimum concentration of hemoglobin in the blood, compatible with life, is 10 g / l.