Tolerance is when, after being exposed to a certain drug for a long period of time, the body can no longer respond to the same dose that used to trigger a biological response, so the dose has to be increased.
Hemoglobin is found in red blood cells and gives the body's blood red pigment. It is formed by the heme group and a protein group (globin). Hemoglobin is responsible for transporting oxygen from the respiratory organs to body tissues.