Erythropoietin (EPO)
Recombinant human erythropoietin (rHuEPO, epoetin alfa/beta) is a glycoprotein hormone that stimulates red blood cell production in bone marrow. Developed for renal anaemia and chemotherapy-induced anaemia, it became the archetypal endurance-doping agent from the 1990s onward, raising haematocrit and aerobic capacity. It is prohibited by WADA at all times.
01 Overview
EPO is produced physiologically by the kidney in response to hypoxia and drives erythropoiesis by binding the EPO receptor on erythroid progenitor cells. Recombinant forms (epoetin alfa, epoetin beta) are well characterised in decades of clinical use for anaemia of chronic kidney disease and cancer. In endurance sport it is misused to expand red cell mass, increasing maximal oxygen uptake and time to exhaustion.\n\nThe central danger is that raising haematocrit thickens the blood: during dehydration and low nighttime cardiac output this substantially raises the risk of thrombosis, stroke, pulmonary embolism and sudden death. A cluster of cyclist deaths in the late 1980s and 1990s is widely attributed to unsupervised EPO use. It is detectable in urine and blood by isoelectric focusing and via the Athlete Biological Passport.
02 Mechanism
Binds the erythropoietin receptor (EPO-R) on erythroid progenitors in bone marrow, activating JAK2/STAT5 signalling that promotes their survival, proliferation and differentiation into mature red blood cells, expanding red cell mass and oxygen-carrying capacity.
03 Dosing
| Tier | Dose | Route | Notes |
|---|---|---|---|
| Doping (illicit) | 20–50 IU/kg | SubQ | Reported illicit micro-dosing regimens; not a recommendation |
| Renal anaemia (medical) | 50–100 IU/kg | SubQ | 3x weekly, titrated to haemoglobin; medical use only |
04 Effects
| Effect | Magnitude | Evidence | |
|---|---|---|---|
| Increased VO2max / aerobic capacityExpanded red cell mass raises oxygen delivery to working muscle, improving maximal aerobic power and time to exhaustion. | +6-12% VO2max | Clinical | |
| Correction of anaemiaIts licensed effect: restores haemoglobin in renal or chemotherapy-related anaemia, reducing transfusion need. | Hb +1-2 g/dL over weeks | Clinical |
05 Side effects
| Effect | Severity | Frequency | Evidence | Countermeasures |
|---|---|---|---|---|
| Thrombosis / stroke / pulmonary embolismRaised haematocrit increases blood viscosity, predisposing to venous and arterial clots, myocardial infarction and stroke, especially when dehydrated or at rest. | Life-threatening | Dose-dependent, common at high haematocrit | Clinical | |
| HypertensionEPO commonly raises blood pressure and can precipitate hypertensive encephalopathy at high doses. | Moderate | Common | Clinical |