The causes of anemia in chronic renal failure, also known as renal anemia, occur in chronic kidney disease and are related to chronic renal failure. There are multiple reasons for this anemia, such as the lack of raw materials for red blood cell production caused by chronic renal failure, including deficiencies in iron, folic acid, and vitamin B1, shortened lifespan of red blood cells, and blood loss including non-gastrointestinal blood loss. Moreover, uremic toxins including parathyroid hormone can suppress the production of red blood cells in the bone marrow. However, the primary cause is the decreased production of erythropoietin by the kidneys during chronic renal failure.