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At a Glance

Why Get Tested?

To help diagnose the cause of anemia; to help diagnose a bone marrow disorder or a condition causing the production of too many red blood cells (polycythemia or erythrocytosis)

When To Get Tested?

When you have anemia that your healthcare practitioner suspects may be caused by decreased red blood cell production; when you are producing too many red blood cells

Sample Required?

A blood sample drawn from a vein in your arm

Test Preparation Needed?


You may be able to find your test results on your laboratory’s website or patient portal. However, you are currently at Testing.com. You may have been directed here by your lab’s website in order to provide you with background information about the test(s) you had performed. You will need to return to your lab’s website or portal, or contact your healthcare practitioner in order to obtain your test results.

Testing.com is an award-winning patient education website offering information on laboratory tests. The content on the site, which has been reviewed by laboratory scientists and other medical professionals, provides general explanations of what results might mean for each test listed on the site, such as what a high or low value might suggest to your healthcare practitioner about your health or medical condition.

The reference ranges for your tests can be found on your laboratory report. They are typically found to the right of your results.

If you do not have your lab report, consult your healthcare provider or the laboratory that performed the test(s) to obtain the reference range.

Laboratory test results are not meaningful by themselves. Their meaning comes from comparison to reference ranges. Reference ranges are the values expected for a healthy person. They are sometimes called “normal” values. By comparing your test results with reference values, you and your healthcare provider can see if any of your test results fall outside the range of expected values. Values that are outside expected ranges can provide clues to help identify possible conditions or diseases.

While accuracy of laboratory testing has significantly evolved over the past few decades, some lab-to-lab variability can occur due to differences in testing equipment, chemical reagents, and techniques. This is a reason why so few reference ranges are provided on this site. It is important to know that you must use the range supplied by the laboratory that performed your test to evaluate whether your results are “within normal limits.”

For more information, please read the article Reference Ranges and What They Mean.

What is being tested?

Erythropoietin (EPO) is a hormone produced primarily by the kidneys, with small amounts made by the liver. EPO plays a key role in the production of red blood cells (RBCs), which carry oxygen from the lungs to the rest of the body. This test measures the amount of erythropoietin in the blood.

The body uses a dynamic feedback system to help maintain sufficient oxygen levels and a relatively stable number of RBCs in the blood.

  • Erythropoietin is produced and released into the blood by the kidneys in response to low blood oxygen levels (hypoxemia). The amount of erythropoietin released depends on how low the oxygen level is and the ability of the kidneys to produce erythropoietin.
  • EPO is carried to the bone marrow, where it stimulates production of red blood cells. The hormone is active for a short period of time and then eliminated from the body in the urine.
  • As oxygen levels in the blood rise to normal or near normal levels, the kidneys slow production of EPO.

However, if your kidneys are damaged and do not produce enough erythropoietin, then too few RBCs are produced and you can becomes anemic. Similarly, if your bone marrow is unable to respond to the stimulation from EPO, then you may become anemic. This can occur with some bone marrow disorders or with chronic diseases, such as rheumatoid arthritis.

If you have a condition that affects the amount of oxygen you breathe in, such as a lung disease, you may produce more EPO to try to compensate for the low oxygen level. People who live at high altitudes may also have higher levels of EPO and so do chronic tobacco smokers.

If you produce too much erythropoietin, which can happen with some benign or malignant kidney tumors and with a variety of other cancers, you may produce too many RBCs (polycythemia or erythrocytosis). This can lead to an increase in the blood’s thickness (viscosity) and sometimes to high blood pressure (hypertension), blood clots (thrombosis), heart attack, or stroke. Rarely, polycythemia is caused by a bone marrow disorder called polycythemia vera, not by increased erythropoietin.

Common Questions

How is the test used?

An erythropoietin (EPO) test is used primarily to help diagnose the cause of anemia. An EPO test is usually ordered in follow up to abnormal results on a complete blood count (CBC), such as a low red blood cell (RBC) count and low hemoglobin and hematocrit. These tests help diagnose anemia and give the health care practitioner clues as to the likely cause of the anemia. Erythropoietin testing is used to help determine if low EPO may be causing and/or worsening the anemia.

If you have chronic kidney disease, an EPO test may be ordered to evaluate the kidneys’ continued ability to produce enough erythropoietin. Testing can help determine whether you should receive erythropoietin replacement therapy. If the erythropoietin level is low, erythropoietin replacement therapy may help increase red cell production in the bone marrow.

Occasionally, an erythropoietin test may be ordered in follow up to CBC results that show an increased number of RBCs, to help diagnose the cause. Testing may help determine whether the excess production of RBCs (polycythemia or erythrocytosis) is due to an overproduction of erythropoietin or some other cause (e.g., JAK2 mutation, bone marrow disorder).

When is it ordered?

An erythropoietin (EPO) test may be ordered when you have anemia that does not appear to be caused by iron deficiency, vitamin B12 or folate deficiency, decreased lifespan of red blood cells (RBCs; hemolysis), or by excessive bleeding. It may be ordered when the RBC count, hemoglobin, and hematocrit are decreased and the reticulocyte count is inappropriately normal or decreased.

If you have chronic kidney disease, erythropoietin levels may be ordered when your health care practitioner suspects that kidney dysfunction could be associated with a decrease in erythropoietin production.

An EPO test may be ordered when a complete blood count shows that you have an increased number of RBCs and a high hematocrit and hemoglobin.

An EPO test may be ordered when a health care practitioner suspects that you have a bone marrow disorder, such as a myeloproliferative neoplasms (MPNs) or myelodysplastic syndrome (MDS).

What does the test result mean?

If you have anemia and erythropoietin levels are low or normal, then your kidneys may not be producing enough EPO.

If you have anemia and erythropoietin levels are increased, then the anemia may be due to iron or vitamin deficiency, or a bone marrow disorder.

If you have too many red blood cells (RBCs) and erythropoietin levels are increased, then it is likely that excess erythropoietin is being produced – either by your kidneys or by other tissues in your body. This condition is called secondary polycythemia.

If you have too many RBCs and erythropoietin levels are normal or low, then it is likely that the polycythemia has a cause that is independent of erythropoietin production. This condition is called primary polycythemia.

Is there a treatment for low EPO?

A synthetic form of erythropoietin (recombinant human erythropoietin or rh-EPO) may be used as a treatment to help increase RBC production in people with chronic kidney disease and other anemias related to bone marrow suppression and/or failure, such as that due to radiation or chemotherapy treatment for cancer. The drug treatment, which is given through a vein (intravenously) or under the skin (subcutaneous injection), is expensive and its stimulation of the bone marrow lasts only a few hours. The synthetic hormone’s use has been promising, helping to decrease the need for blood transfusions and improving the quality life for many affected people.

In June 2011, The U.S. Food and Drug Administration (FDA) recommended that healthcare professionals adjust the ESAs for more conservative dosing in patients with chronic kidney disease (CKD) to improve the safety of these drugs. The data indicated increased risks of cardiovascular events (e.g., heart attacks and strokes) with ESAs in this patient population.

If you produce an abnormal form of hemoglobin, such as may occur with thalassemia, or if you have a bone marrow disorder, then erythropoietin replacement therapy will not help resolve the anemia.

Can adequate erythropoietin production by my kidneys be restored?

Not directly. If your low EPO is due to a temporary kidney condition, then it may resolve as the kidney condition resolves. In many cases, however, low EPO is due to chronic kidney disease and will not get better over time. Your health care practitioner will work with you to address and minimize the effects of the resulting anemia and may treat you with synthetic erythropoietin (i.e., erythropoietin replacement therapy).

Why isn't erythropoietin measured to monitor erythropoietin drug therapy?

It is not used because it is the effect on the bone marrow – reflected by increased RBC and reticulocyte production and increasing hemoglobin – that is important in the resolution of anemia, not the concentration of erythropoietin in the blood. The amount needed will vary from person to person depending on their condition and the responsiveness of their bone marrow.

I’ve heard some athletes are tested for EPO. Why?

Synthetic erythropoietin is also being used by some athletes as a form of “blood doping.” Those who use it are trying to increase their endurance and oxygen capacity by increasing the number of RBCs in their blood. This use of the drug can be dangerous, resulting in hypertension and increasing the viscosity of the blood. Its use has been prohibited by most sports organizations, including the International Association of Athletics Federations, and erythropoietin is now being tested for as part of the Olympics anti-doping program.

Is there anything else I should know?

If anemia is due to a vitamin B12, folate, or iron deficiency, then the anemia may persist even when enough erythropoietin is produced. The red blood cells (RBCs) produced in these deficiencies may not be normal in size, shape, and/or hemoglobin content.

Pregnant women, chronic smokers, and people with lung disease, or who live at high altitudes may have increased levels of erythropoietin.

View Sources

Sources Used in Current Review

2020 review performed by Hoda Hagrass MD, Ph.D., Assistant Professor of Pathology and Medical Director of Clinical Chemistry and Immunology, UAMS, and ACH.

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Kalantar-Zadeh K. History of Erythropoiesis-Stimulating Agents, the Development of Biosimilars, and the Future of Anemia Treatment in Nephrology. Am J Nephrol. 2017;45(3):235-247. doi: 10.1159/000455387. Epub 2017 Feb 1. PMID: 28142147; PMCID: PMC5405152.

World Anti-doping Agency. UFC Prohibited List (August 31, 2019). Available online at  https://ufc.usada.org/wp-content/uploads/UFC-Prohibited-List.pdf. Accessed on 10/5/2020.

Kaushansky K. Hematopoiesis and hematopoietic growth factors. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 147.

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