Kidney disease is a major cause of low red blood cell count, a condition medically known as anemia. The kidneys perform many functions beyond filtering waste and excess fluid from the blood, playing a direct role in maintaining the body’s red blood cell supply. When kidney function declines due to disease, this production process is severely disrupted, leading to a deficiency in the blood’s oxygen-carrying capacity.
Anemia of Chronic Kidney Disease
The resulting condition is termed Anemia of Chronic Kidney Disease (CKD), a common and often serious complication of progressive kidney failure. Anemia prevalence and severity increase predictably as kidney function worsens. While approximately 8% to 15% of patients with early-stage CKD may experience anemia, this percentage can climb to over 50% in the most advanced stages of the disease. This type of anemia differs from others because its primary cause is a hormonal deficiency rather than blood loss or a lack of dietary iron alone. The condition is classified as a normocytic, normochromic anemia, meaning the red blood cells produced are of normal size and color but are too few in number.
The Role of Erythropoietin in Red Blood Cell Production
The direct link between kidney disease and anemia is the kidney’s role as the main producer of the hormone Erythropoietin (EPO). EPO is a glycoprotein hormone synthesized primarily by specialized interstitial fibroblasts in the renal cortex. These cells act as sensors, constantly monitoring the oxygen levels in the blood circulating through the kidneys.
When the oxygen partial pressure (pO2) drops below a certain threshold, the kidney cells increase their production and secretion of EPO. This hormone then travels through the bloodstream to the bone marrow, which is the body’s primary site for blood cell formation. EPO acts as a signal, instructing the bone marrow to accelerate the production and maturation of red blood cells (erythropoiesis).
In a person with chronic kidney disease, the damaged renal tissue loses the ability to produce adequate amounts of EPO. This results in a deficiency of the hormone, sometimes called relative EPO deficiency, which is the most significant factor contributing to CKD-related anemia. Without this hormonal signal, the bone marrow receives insufficient stimulation and slows or stops its production of new red blood cells.
Recognizing the Symptoms of Low Red Blood Cell Count
The physical symptoms of low red blood cell count, or anemia, are caused by the reduced ability of the blood to carry oxygen to the body’s tissues and organs.
Common Symptoms of Anemia
- Profound fatigue and general weakness that does not improve with rest.
- Shortness of breath, as the body attempts to compensate for the reduced oxygen-carrying capacity by increasing the breathing rate.
- The skin may take on a pale appearance because of the reduced number of red blood cells circulating near the surface.
- Difficulty concentrating and dizziness, which occur when the brain receives a diminished oxygen supply.
- Unusual sensitivity to cold, known as cold intolerance.
- A pounding or irregular heartbeat, as the heart may have to work harder to circulate the limited oxygen supply.
Treatment and Management Strategies
The primary treatment for anemia of chronic kidney disease targets the root cause, which is the lack of the EPO hormone. This is accomplished through the use of Erythropoiesis-Stimulating Agents (ESAs), which are synthetic, recombinant forms of natural EPO. These injectable medications mimic the action of the hormone, traveling to the bone marrow to stimulate the production of red blood cells. ESAs are typically considered when the hemoglobin level drops below 10 g/dL, with the goal of reducing the need for blood transfusions.
An equally important part of the management strategy is iron supplementation, as iron is a necessary building block for producing hemoglobin within the new red blood cells. The use of ESAs increases iron utilization, meaning the body needs more iron to effectively create new blood cells. Many CKD patients develop iron deficiency due to poor absorption and other factors, making supplementation with oral or intravenous iron preparations necessary alongside ESA therapy.
For patients on hemodialysis, intravenous iron is often preferred because kidney disease can impair the body’s ability to absorb oral iron supplements. Newer medications, such as Hypoxia-Inducible Factor–Prolyl Hydroxylase Inhibitors (HIF-PHIs), are also available, which work by stabilizing a protein that increases the body’s natural EPO production and improves iron metabolism. Management also involves general supportive measures, including dietary guidance and rest, to help the patient manage the symptoms and improve the overall quality of life.