When one moves up to a higher altitude the levels of oxygen decrease and hence, the body faces a shortage of oxygen. Since red blood cells are the carriers of oxygen it becomes important for the body to increase the production of red blood cells in order to cope up with low levels of oxygen.
Erythropoietin is a hormone that is responsible for stimulating the production of red blood cells in the bone marrow and hence in conditions of hypoxia that are low oxygen levels the production of RBCs is increased due to the increased release of erythropoietin from the kidney.
