Erythropoietin (EPO)
Kidney hormone that stimulates the bone marrow to produce red blood cells
Also known as
Definition
Erythropoietin, or EPO, is a hormone made by cells in the kidney. It signals stem cells in the bone marrow to produce more red blood cells. When the oxygen level in the blood drops, these cells release more EPO. The blood test measures the EPO concentration in serum and helps narrow down the cause of anemia, a high red blood cell count (polycythemia) or other bone marrow disorders.
| Parameter | Value |
|---|---|
| Unit | mU/ml (= U/l) |
| Reference Range | Typical for adults: 2.6–18.5 mU/ml. Labs and assays differ; the range printed on your own report is what counts. Discuss any deviation with your doctor. |
Agree on your personal target range with your doctor.
1 mU/ml equals 1 U/l (IU/l), so 2.6–18.5 mU/ml is 2.6–18.5 U/l. US reports use mIU/mL.
↓ What a low value means
A lower-than-usual EPO level can occur with chronic kidney disease, anemia of chronic disease or polycythemia vera, a bone marrow disorder in which too many red blood cells are produced. What a single value means depends on the full blood count and other findings; discuss it with your doctor.
↑ What a high value means
A raised EPO level can be linked to secondary polycythemia, an increased production of red blood cells in response to a trigger such as a low blood oxygen level, for example at high altitude, and rarely to a tumor that releases EPO. With anemia, when there are too few red blood cells, the body also produces more EPO. Your doctor interprets the result together with hemoglobin, red blood cell count and other findings.
When to test
The test is ordered specifically to help narrow down the cause of anemia, a high red blood cell count or another bone marrow disorder. It requires a blood sample from a vein; no special preparation is needed.
Frequently asked questions
Why is EPO often high with anemia? +
With anemia there are too few red blood cells. When the blood oxygen level falls as a result, kidney cells release more EPO to stimulate new production in the bone marrow. With chronic kidney disease, by contrast, the EPO level can be low.
Can a stay at high altitude change the EPO level? +
It can. A low blood oxygen level, as can occur at high altitude, is one of the triggers for increased red blood cell production. If you spent time in the mountains before your blood draw, mention it when you discuss your results.
Can EPO medicines change other blood values? +
Yes. Erythropoietin is also used as a medicine and is one of the drugs that can raise the red blood cell count. Tell the practice about all medicines you take before your blood draw.
Do I need to prepare for the test? +
No, no special preparation is needed. The test uses a blood sample.
Erythropoietin (EPO)
Sources
Last updated: October 05, 2026
This information is for orientation only and does not replace medical advice. Reference ranges can vary by laboratory, method and country.