How can chronic kidney disease cause anemia?

Chronic kidney disease leads to anemia primarily because of a reduced ability of the kidneys to produce erythropoietin.123

Erythropoietin is a hormone produced largely by the kidneys that acts as a critical signal to the bone marrow, stimulating the production of red blood cells. In a healthy body, this mechanism functions like a thermostat: when oxygen levels in the blood decrease, the kidneys increase erythropoietin production to boost red blood cell output.245

As chronic kidney disease progresses, the nephrons—the functional units of the kidney—are damaged and lost. This deterioration impairs the kidney's capacity to manufacture sufficient erythropoietin. Without adequate levels of this hormone, the bone marrow cannot produce enough red blood cells to maintain normal levels, resulting in the development of anemia.1352