Erythropoietin (EPO) Test

Measuring blood levels of erythripoietin, a hormone involved in red blood cell production, can diagnose some medical conditions.

Erythropoietin (EPO) is a hormone secreted by specialized cells in the kidney that stimulate the bone marrow to manufacture red blood cells (erythrocytes).

Red blood cells in the blood stream contain hemoglobin that transport oxygen from air in the lungs and deliver it to every cell in the body. Those red blood cells are produced in the bone marrow and have a lifespan of about three months. Fibroblasts in the kidney are always making erythropoietin to keep the bone marrow active in making new red blood cells to replace the aging ones.

When the oxygen delivery system fails to deliver adequate oxygen, whether it is because of a lack of adequate red blood cells (anemia), or lack of available oxygen (hypoxia), the kidney fibroblasts increase their production of erythropoietin.

The kidney may increase erythropoietin levels in patients with chronic anemia, patients with COPD who have chronically low blood oxygen levels, or in people who live at high altitude where there is less oxygen in the air.

Patients who have chronic kidney disease may not be able to produce adequate amounts of erythropoietin leading to anemia.

In the fetus, erythropoietin is produced by the liver, but after birth, the kidney becomes the source of the hormone. The liver does retain some capability of producing some erythropoietin.

The erythropoietin hormone in the blood can be measured. The test is ordered to help determine the cause of an unexplained anemia (low red blood cell count).

The reason that a patient is anemic is often diagnosed without the need for extensive testing. Examples include blood loss, iron deficiency, and vitamin B12 or folate deficiencies. But when the cause is uncertain, testing erythropoietin levels can be helpful in making the diagnosis.

However, the erythropoietin level by itself cannot make a diagnosis. It needs to be interpreted in the context of the patient’s situation and along with other blood tests.

Not only can the test help in anemia, but it is also helpful when the patient has too many red blood cells (polycythemia), to help find the diagnosis.

Do I need to fast before an erythropoietin blood test?

There is no need to fast for an EPO test. It is a routine test with blood commonly drawn from a vein in the arm.

The normal range for erythropoietin levels range from 2.6 to 18.5 milliunits per milliliter (mU/mL). There may be some variation between laboratories. It is important to review the results with your health care provider.

What does high erythropoietin levels mean?

The body will increase its erythropoietin production in response to chronic hypoxia (low blood oxygen levels). This can include patients with chronic lung diseases like COPD or people who live at high altitudes.

Levels are elevated in patients with anemia of many types like blood loss, iron deficiency, or thalassemia.

Elevated levels are also seen with bone marrow suppression and in pregnancy.

What does low erythropoietin levels mean?

Low erythropoietin levels are commonly found in patients with chronic kidney disease.

Chronic inflammatory conditions like rheumatoid arthritis can cause lower levels, as can HIV infection and some cancers.

Polycythemia vera is a rare blood disorder, where the bone marrow makes too many red blood cells.

Erythropoietin has been misused as a performance-enhancing drug in athletes to increase red blood cell production in the bone marrow and to help increase the oxygen carrying capacity of blood. Higher levels of oxygen delivered to muscle allows for better endurance. Its use has been documented in elite athletes in sports like cycling, speedskating, swimming, and running.

There are significant potential complications in the use of erythropoietin when it is not indicated. Increased red blood cell counts can cause the blood to sludge because it too thick. This can lead to stroke, heart attack, and increased risk of blood clot. Hypertensive crisis is also a potentially dangerous complication.

This type of blood doping is illegal in all sporting events and can be harmful to the athlete.

Some patients may benefit from increased erythropoietin in their bodies to help stimulate the bone marrow to produce red blood cells.

The hormone is injected either under the skin (subcutaneously) or into a vein (intravenously) depending upon the situation.

The injections may be required 1 to 3 times per week.

The reason to use erythropoietin is to treat certain patients with low red blood cell counts, with the hope of stimulating the bone marrow to produce more red cells and increase oxygen carrying capacity of the blood.

Most often erythropoietin is used in patients in chronic kidney failure, including dialysis patients, and in some cancer patients undergoing chemotherapy.

Other patients who may benefit include those who are anemic and undergoing elective surgery so that they won’t require a blood transfusion, and HIV patients receiving AZT therapy.