Erythropoietin (EPO)
The kidney hormone that drives red-cell production: recombinant epoetin has treated anaemia since 1989, under a boxed warning about death, heart attack, stroke and tumour growth
Erythropoietin is a glycoprotein hormone of 165 amino acids, made mainly by the kidneys, that keeps red blood cells coming. Too little of it causes the anaemia of chronic kidney disease. Recombinant epoetin alfa (Epogen, Procrit) was approved in the US in 1989 and is now joined by biosimilars. It raises haemoglobin and cuts transfusions, but aiming for high haemoglobin raised the risks of death, heart attack, stroke and clots, which is why its label carries a boxed warning. It is also a classic doping agent, prohibited in sport.
What is it?
Erythropoietin is the signal that tells the bone marrow to make red blood cells. It is a 165-amino-acid glycoprotein with four sugar chains, about 30.4 kDa, produced mainly by the kidneys under the control of hypoxia-inducible factors, and it is essential for the survival and multiplication of red-cell progenitors. When the kidneys fail, erythropoietin falls, which is the main cause of the anaemia of chronic kidney disease.
Recombinant epoetin alfa was approved in the US on June 1, 1989, sold as Epogen and Procrit. Its label covers anaemia from chronic kidney disease, from zidovudine in HIV and from chemotherapy, among other uses. In a study of 1,557 anaemic patients with kidney disease not on dialysis, once-weekly injections raised mean haemoglobin from 9.1 to 11.6 g/dL, with 89.8% responding and the share needing transfusion falling from 11.1% to 3.7%. The patents have since expired: FDA approved the biosimilar Retacrit in 2018, and in a trial of 418 dialysis patients switching to it kept haemoglobin in range as well as staying on Epogen.
More was not better. Trials in chronic kidney disease found greater risks of death, serious cardiovascular events and stroke when haemoglobin was pushed to higher targets, and a later analysis of the CHOIR trial found the lowest risk in patients who reached middle haemoglobin levels on the lowest doses. Epogen's label now carries a boxed warning covering death, heart attack, stroke, venous thromboembolism, thrombosis of vascular access and tumour progression or recurrence. A rarer harm, pure red-cell aplasia from antibodies against erythropoietin, rose after 1998 and was linked to one subcutaneous formulation; a later registry of 15,333 patients found it rare with every product.
Outside anaemia, results have been disappointing. High-dose epoetin did not improve outcomes in newborns with hypoxic-ischaemic encephalopathy, and brain-injury patterns on MRI were the same as on placebo. Oral HIF drugs such as roxadustat now raise haemoglobin as well as epoetin in dialysis patients. In sport, erythropoietin is prohibited; in one altitude study, low-dose epoetin before ascent did not improve haemoglobin mass or performance.
Mechanism of Action
Erythropoietin keeps red-cell precursors alive and dividing. Its recombinant forms do the same, which is both their benefit and their risk.
Red-cell production
Erythropoietin is essential for the viability and proliferation of erythrocytic progenitors in the bone marrow; raising it raises haemoglobin and reduces the need for transfusion.
The kidney's oxygen sensor
The kidneys are its main source, and hypoxia-inducible factors control its synthesis; kidney failure lowers it, and oral HIF prolyl hydroxylase inhibitors such as roxadustat raise the body's own erythropoietin instead.
Thrombosis and cardiovascular risk
Its label's boxed warning reflects controlled trials in which targeting higher haemoglobin increased death, serious cardiovascular reactions and stroke; the CHOIR analysis linked the lowest risk to moderate haemoglobin reached on low doses.
Antibodies and pure red-cell aplasia
Rarely, antibodies against erythropoietin neutralise both the drug and the body's own hormone, causing pure red-cell aplasia; risk varied with formulation and route, and it is a contraindication to further erythropoietin protein drugs.
Published Research
These are studies of erythropoietin read from their PubMed abstracts, most of them of epoetin alfa: its physiology, its use in kidney disease, the biosimilar switch, the red-cell aplasia episode, comparisons with oral HIF drugs, and trials outside anaemia.
Physiology and pharmacology
Human erythropoietin is a 30.4 kDa glycoprotein of 165 amino acids with four glycans, made mainly by the kidneys under HIF control and essential for erythroid progenitors. Deficiency is the primary cause of anaemia in chronic kidney disease; epoetins also treat chemotherapy-induced anaemia, may increase thromboembolism, and biosimilars followed the original patents' expiry.
Once-weekly epoetin alfa in 1,557 patients
Anaemic adults with kidney disease not on dialysis received 10,000 U subcutaneously once a week for 16 weeks, with titration to 20,000 U allowed. Among 1,338 evaluable patients, mean haemoglobin rose from 9.1 to 11.6 g/dL, 89.8% responded, transfusion need fell from 11.1% to 3.7%, and quality-of-life scores improved (all P<0.0001).
CHOIR: dose, haemoglobin and cardiovascular events
In a post hoc analysis of 1,244 CHOIR participants, weekly epoetin alfa doses ranged 143-fold. The composite of death, heart-failure admission, stroke or myocardial infarction was least likely in those who reached haemoglobin between 11.5 and 12.7 g/dL on the lowest doses (under 5,164 units a week).
Pure red-cell aplasia by product
Antibody-mediated pure red-cell aplasia rose sharply after 1998 in patients with kidney disease on recombinant erythropoietin. Using manufacturers' exposure data to 2003, risk did not differ between Epogen, Procrit and Aranesp, while albumin-free Eprex given subcutaneously carried the greatest risk; the authors advised against giving it subcutaneously in kidney disease.
PRIMS: 15,333 patients followed for red-cell aplasia
In a multinational registry after Eprex's subcutaneous use was restored in the EU, five cases of antibody-mediated pure red-cell aplasia were confirmed: 35.8 per 100,000 patient-years with Eprex against 14.0 with NeoRecormon or Aranesp, a difference that was not significant (rate ratio 2.56, 95% CI 0.43 to 15.31).
Switching dialysis patients to biosimilar Retacrit
In a randomised non-inferiority trial at US dialysis centres, 418 patients switched from intravenous Epogen to Retacrit or stayed on Epogen for 24 weeks. Haemoglobin stayed in the 9 to 11 g/dL target 61.9% of the time on Retacrit and 63.3% on Epogen (difference -1.4%, within the -12.5% margin), with similar doses and safety.
Oral roxadustat against epoetin alfa on dialysis
In an open-label phase 3 trial of 2,133 dialysis patients, haemoglobin rose by 0.77 g/dL on roxadustat and 0.68 on epoetin alfa over weeks 28 to 52, meeting non-inferiority; adverse events (85.0% against 84.5%) and serious adverse events (57.6% against 57.5%) were similar.
HEAL: newborns with hypoxic-ischaemic encephalopathy
In the HEAL trial, high-dose epoetin alfa (1,000 U/kg for five doses) alongside cooling did not improve overall outcomes. This secondary analysis of MRI in 470 of 500 infants found similar injury to the deep grey nuclei, cortex, white matter, brainstem and cerebellum on epoetin and placebo, and similar injury patterns.
Epoetin before altitude: no gain
Thirty-nine adults received placebo, intravenous iron or epoetin alfa 50 IU/kg three times a week for about 3.5 weeks at sea level, then spent 14 days at 3,094 m. Haemoglobin mass rose at altitude in every group without differences between treatments, and running performance and mountain sickness were unaffected by treatment.
Dosing Data
Epoetin alfa is dosed by weight and haemoglobin response under the label's monitoring rules. The lowest dose that avoids transfusion is the target.
Educational information, not medical advice. Each dose above is tagged with its source: an approved label, a published human study, animal data, or amounts reported by users. None is a recommendation for you. An unapproved compound has no established safe or effective human dose, and products sold for “research use only” are not made or tested for people. Talk to a doctor before acting on anything on this site, including before you start, stop or change any medicine or dose. Full medical disclaimer.
Side Effects & Contraindications
Reported Side Effects
From the Epogen label and the studies above.
Contraindications & Cautions
From the Epogen label; a clinician decides.
Legal Status
Epoetins are approved prescription medicines in the US and the EU, and erythropoietin is prohibited in sport.
Frequently Asked Questions
?What is erythropoietin?
A 165-amino-acid glycoprotein hormone, made mainly by the kidneys, that drives red blood cell production. Recombinant forms, the epoetins, treat anaemia.
?What is it approved for?
Epoetin alfa (Epogen, Procrit) is approved for anaemia from chronic kidney disease, from zidovudine in HIV and from chemotherapy, among other uses. It was first approved in the US in 1989.
?Why does it carry a boxed warning?
In controlled trials, pushing haemoglobin to higher targets increased the risks of death, heart attack, stroke and blood clots, and in some cancers of tumour growth. The label directs the lowest dose that avoids transfusion.
?Is there a biosimilar?
Yes. FDA approved Retacrit (epoetin alfa-epbx) in 2018; in a trial of 418 dialysis patients, switching to it kept haemoglobin in range as well as staying on Epogen.
?Does erythropoietin improve athletic performance?
It raises haemoglobin, which is why it is prohibited in sport. In one altitude study, low-dose epoetin given for about 3.5 weeks before ascent did not improve haemoglobin mass or running performance compared with placebo.
?Why is it on a peptide site?
It is a glycoprotein hormone, a large peptide chain with sugars attached, and it sits beside ARA 290, a small peptide engineered from it, in our encyclopedia.
References
- [fda-pi] Amgen. EPOGEN (epoetin alfa) injection, US prescribing information: boxed warning (death, myocardial infarction, stroke, venous thromboembolism, thrombosis of vascular access, tumor progression or recurrence); indications; contraindications (uncontrolled hypertension, PRCA after erythropoietin protein drugs, serious allergic reactions, benzyl alcohol in neonates); half-life 4 to 13 hours IV in CKD. DailyMed version effective June 23, 2026; read September 30, 2026.
- [pubmed] Jelkmann W. "Physiology and pharmacology of erythropoietin." Transfus Med Hemother, 2013;40(5):302-9. PMID: 24273483.
- [pubmed] Provenzano R, et al. "Once-weekly epoetin alfa for treating the anemia of chronic kidney disease." Clin Nephrol, 2004;61(6):392-405. PMID: 15224803.
- [pubmed] McCullough PA, et al. "Cardiovascular toxicity of epoetin-alfa in patients with chronic kidney disease." Am J Nephrol, 2013;37(6):549-58. PMID: 23735819.
- [pubmed] Cournoyer D, et al. "Anti-erythropoietin antibody-mediated pure red cell aplasia after treatment with recombinant erythropoietin products: recommendations for minimization of risk." J Am Soc Nephrol, 2004;15(10):2728-34. PMID: 15466278.
- [pubmed] Macdougall IC, et al. "Incidence of erythropoietin antibody-mediated pure red cell aplasia: the Prospective Immunogenicity Surveillance Registry (PRIMS)." Nephrol Dial Transplant, 2015;30(3):451-60. PMID: 25239637.
- [pubmed] Thadhani R, et al. "Switching from Epoetin Alfa (Epogen®) to Epoetin Alfa-Epbx (RetacritTM) Using a Specified Dosing Algorithm: A Randomized, Non-Inferiority Study in Adults on Hemodialysis." Am J Nephrol, 2018;48(3):214-224. PMID: 30196301.
- [pubmed] Fishbane S, et al. "Roxadustat Versus Epoetin Alfa for Treating Anemia in Patients with Chronic Kidney Disease on Dialysis: Results from the Randomized Phase 3 ROCKIES Study." J Am Soc Nephrol, 2022;33(4):850-866. PMID: 35361724.
- [pubmed] Wisnowski JL, et al. "Brain Injury Outcomes after Adjuvant Erythropoietin Neuroprotection for Moderate or Severe Neonatal Hypoxic-Ischemic Encephalopathy: A Report from the HEAL Trial." Dev Neurosci, 2024;46(5):285-296. PMID: 37906983.
- [pubmed] Bradbury KE, et al. "Impact of intravenous iron or exogenous erythropoietin on hemoglobin mass, exercise performance, and acute mountain sickness during altitude acclimatization." J Appl Physiol (1985), 2025;139(4):954-963. PMID: 40912897.
- [fda] FDA. Drugs@FDA (openFDA): Epogen/Procrit BLA 103234 (June 1, 1989); Retacrit BLA 125545 (May 15, 2018); Aranesp BLA 103951 (September 17, 2001); Mircera BLA 125164 (November 14, 2007). Read September 30, 2026.
- [other] European Medicines Agency. Medicines register: epoetins centrally authorised include Abseamed, Binocrit, Epoetin Alfa Hexal, Retacrit, Silapo, NeoRecormon, Biopoin and Eporatio, with Aranesp and Mircera. Read September 30, 2026.
Sources & Citations
Every study on this page was read from its PubMed record. Indications, the boxed warning and pharmacokinetics come from the Epogen label on DailyMed; approval dates from FDA's Drugs@FDA database and EMA's register, read September 30, 2026. Grey Peptides sells nothing and links to no vendor.
Medical Disclaimer: This content is for educational and informational purposes only. It is not medical advice, and nothing here is an instruction to obtain or use any compound. Talk to a licensed clinician about your own situation.