What do the kidneys do besides filtering waste? Many people are surprised to learn that the kidneys also play a key role in red blood cell production.
This article explains how the kidneys help make red blood cells, what erythropoietin (EPO) is, and why kidney disease can lead to renal anaemia.
The kidneys are bean-shaped organs located in the lower back, one on each side of the spine. Most people have two kidneys, but some are born with only one. A person can live a normal, active life with a single healthy kidney.
Although the kidneys are best known for removing waste from the blood, they have several other important functions. One of these is their role in blood production.
The kidneys produce a hormone called erythropoietin (EPO).
A hormone is a chemical messenger that travels through the bloodstream to send instructions to other parts of the body.
What Does EPO Do?
EPO travels from the kidneys to the bone marrow, found inside large bones. The bone marrow is where red blood cells are made.
EPO signals the bone marrow to:
This makes EPO one of the seven major functions of the kidneys.
Red blood cells carry oxygen from the lungs to the rest of the body. If oxygen levels drop too low, tissues and organs can be damaged.
The kidneys can sense when oxygen levels in the blood are reduced. In response, they release more EPO, which increases red blood cell production and improves oxygen delivery.
Negative Feedback Control
EPO production works through a negative feedback system:
This system helps keep oxygen levels stable.
Renal anaemia is a common complication of chronic kidney disease (CKD), especially in Stage 4 and Stage 5 CKD.
What Causes Renal Anaemia?
Anaemia simply means there are too few red blood cells to carry enough oxygen around the body.
Symptoms can be mild and non-specific, including:
Renal anaemia is diagnosed with a blood test called a full blood count (FBC).
Doctors look at:
Treatment aims to increase red blood cell production by replacing or stimulating EPO.
Common treatments include:
Treatment choice depends on the patient and stage of kidney disease.
The kidneys do more than filter waste—they are essential for red blood cell production. By producing erythropoietin (EPO), the kidneys help maintain healthy oxygen levels in the body.
When kidney function declines, reduced EPO production can lead to renal anaemia, a common and treatable complication of chronic kidney disease.
Watch this video to learn more about erythropoietin
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