Blood many invertebrates, these oxygen-carrying proteins are freely soluble in the blood; in vertebrates they are contained in specialized red blood cells, allowing for a higher concentration of respiratory pigments without increasing viscosity or damaging blood filtering organs like the kidneys. Giant tube worms have unusual hemoglobins that allow them to live in extraordinary environments. These hemoglobins also carry sulfides normally fatal in other animals. The coloring matter of blood (hemochrome) is largely due to the protein in the blood responsible for oxygen transport. Different groups of organisms use different proteins. Hemoglobin is the principal determinant of the color of blood
Blood doping or storage is another issue. Contamination was seen in 1 in every 500,000 transfusions of red blood cells in 2002. Blood contamination can lead to septicemia or an infection that affects the whole body. Certain medications used to increase red blood cells can reduce liver function and lead to liver failure, pituitary problems, and increases in cholesterol levels. Blood doping Blood doping is the practice of boosting the number of red blood cells in the bloodstream in order to enhance athletic performance. Because such blood cells carry oxygen from the lungs to the muscles, a higher concentration in the blood