Hemoglobin vs Hematocrit
Hemoglobin is a protein present mainly in red blood cells of almost all vertebrates. Hematocrit, on the other hand, is a measurement related to total blood count. Both of these are used to diagnose anemia and hence mistaken to be the same thing frequently.
Hemoglobin is a metallo-protein containing a heme group and globin proteins. Heme group contains iron and has the ability to get bound to oxygen with great affinity. Hemoglobin is symbolized by Hb. It is present in vertebrates and some invertebrates. The function of hemoglobin is mainly transporting oxygen from lungs (or gills) to other tissues as oxyhemoglobin, to be used in cellular respiration. From tissues, carbon dioxide is transported back to the lungs as carboxyhemoglobin.
Hemoglobin also has the ability to transport nitric oxide molecules; a crucial player in cell signaling processes. Hemoglobin is responsible for the red colour of red blood cells. It is also present in some neurons, macrophages, alveolar cells etc., but the functions are different from hemoglobin present in red blood cells. One such function is working as an antioxidant in iron metabolism. In mammals, hemoglobin makes up to 97% of the dry weight of red blood cells and up to 35% of the wet weight. Presence of hemoglobin in blood has increased blood’s ability of transporting oxygen by seventy fold when compared to oxygen merely being dissolved in the blood. When red blood cell count drops it is an indication to the low level of red blood cells or heme production which results in anemia, and the frequent symptoms are fatigue, lack of concentration, exercise intolerance. Having very low hemoglobin counts can be lethal due to low oxygen supply to tissues.
Hematocrit abbreviated as HCT or Ht is also known as erythrocyte volume fraction (EVF) or packed cell volume (PCV). What it measures is the percentage volume of red blood cells in the blood. The count is generally 45% for men and 40% women. Hemoglobin count is actually a part of hematocrit. It is observed that hematocrit is independent of the body size in mammals.
There are many ways of determining hematocrit. The classical method is centrifuging heparinized blood and separating blood into different layers and calculating volume percentage using layer heights. The modern method is using an automated analyzer. In a patient who is under red blood cell supplements hematocrit may be artificially high. In a patient who is under saline supply hematocrit is low due to the dilution of blood. High hematocrit is a sign of dengue shock syndrome. Hematocrit and hemoglobin level changes parallel to each other. Therefore, one of the two is enough to determine anemia.
What is the difference between Hemoglobin and Hematocrit?
• Hemoglobin is a protein but hematocrit is not a protein; it is a measurement.
• Hemoglobin is a part of hematocrit because hematocrit is a measure of total red blood cells where hemoglobin is only a component.
• Hemoglobin count and hematocrit changes parallelly. (If one is low, the other too is low and vice versa.)