This is what makes your blood red. It carries oxygen in the blood.
The red blood cells or RBCs make our blood red and carry out the important function of transporting oxygen in our blood. RBCs are one of the key components of our blood, other components being blood plasma, white blood cells and platelets. RBCs contain hemoglobin, which carries oxygen in our blood and is responsible for the red color of our blood. Another important function of RBCs (or erythrocytes) is to carry carbon dioxide to the lungs so that it can be exhaled out of our body. RBCs have an average life of about 120 days and millions of RBCs are produced every day in our body. If our body is not generating enough RBCs, the condition can result in different forms of anemia, including sickle-cell anemia.
Hope this helps.