Erythropoietin

Ranges depend on the laboratory method (some use 2.6 to 18.5 or 4.3 to 29 mIU/mL) and the value is only meaningful when read against the haemoglobin at the same time; use the range your lab printed.

Erythropoietin is a hormone made mainly by the kidneys that tells the bone marrow to make red blood cells. When oxygen levels or the red cell count fall, the kidneys make more of it. The test measures the amount circulating in the blood.

Doctors request it when the haemoglobin is unexpectedly high, to help work out whether the bone marrow is overproducing on its own or is being driven by the hormone, and sometimes when the haemoglobin is low in kidney disease. It is always read against the haemoglobin measured at the same time.

• Anaemia of most causes, as the expected response
• Living at altitude, lung disease, sleep apnoea and smoking, where oxygen levels are lower
• Some kidney cysts and tumours, and rarely other tumours, that make the hormone
• Some bone marrow conditions where the marrow is not responding
• Pregnancy

• Long-term kidney disease, where the kidneys make less
• Polycythaemia vera, a bone marrow condition where red cells are made without the hormone's signal
• Long-term inflammatory illness
• Some medicines that suppress the response

• The level depends on the haemoglobin at the time, so it cannot be interpreted alone
• Time of day and recent exercise shift it a little
• Different laboratory methods give different numbers
• A value within the range is the usual finding even when the haemoglobin is high

No fasting needed. Ideally taken before any blood transfusion or erythropoietin injections, and alongside a full blood count.

Written by a UK consultant physician. Typical UK adult reference ranges; your laboratory's own printed range takes precedence.