HowStuffWorks explains that the hormone erythropoietin stimulates the production of red blood cells. The kidneys produce up to 90 percent of the erythropoietin in the human body, according to HowStuffWorks, and virtually any stimulus that causes a reduction in oxygen, such as lung disease, stimulates the kidneys to produce and secrete erythropoietin. Eventually, the erythropoietin reaches the blood marrow, where new red blood cells are created, according to the Merck Manual for Home Health.
Mdhealth.com states that a healthy human body produces over 2.4 million red blood cells every second. These cells survive for about four months, at which time HowStuffWorks explains that the spleen and liver remove them with the help of macrophages. However, some people suffer from a condition called anemia, in which they do not produce enough red blood cells. Anemia.org explains that those afflicted can take any of several medicines that increase the rate of red blood cell production.
Red blood cells are the most numerous cells in the human blood. According to HowStuffWorks, the red blood cells carry hemoglobin, which is the molecule primarily responsible for transporting oxygen through the body. Red blood cells have a number of unusual adaptations that allow them to perform their function. For example, mature red blood cells have no nuclei and are very malleable cells, which allow them to move through the tiny capillaries of the body.