Erythropoietin (EPO)

Erythropoietin is a type of protein called a growth factor. It is used to treat a low number of red blood cells (anaemia) due to cancer or its treatment.

What is erythropoietin?

Erythropoietin is a type of protein called a growth factor. It stimulates the bone marrow to make red blood cells. Red blood cells contain a protein called haemoglobin (Hb). It carries oxygen around the body.

The body makes erythropoietin naturally. But it is also made as a drug to treat a low number of red blood cells (anaemia). 

Anaemia can cause symptoms such as:

  • pale skin
  • lack of energy
  • feeling breathless
  • feeling dizzy and light-headed.

Anaemia can be caused by cancer, or by cancer treatments such as  chemotherapy

More information about this treatment

This information is correct at time of publishing. But sometimes the types of cancer this treatment is used for, or treatment side effects, may change between revision dates.

You can talk to your cancer team if you want more detailed information about this treatment. Or visit the electronic Medicines Compendium (eMC) website, which has patient information leaflets (PIL) for individual drugs.

When is erythropoietin used?

Doctors usually treat anaemia with a blood transfusion to replace red blood cells. But they may use erythropoietin instead if:

  • the cancer treatment means blood transfusions are needed often
  • blood transfusions are not suitable
  • the anaemia is caused by a type of blood cancer called myelodysplasia.

There are different types of erythropoietin treatments. They are often called EPO. Treatments include:

  • epoetin alfa – for example, Eprex®
  • epoetin beta – for example, NeoRecormon®
  • epoetin zeta – for example, Retacrit®
  • darbepoetin alfa (Aranesp®).

Your doctor will talk to you about erythropoietin and its possible side effects before you agree (consent) to have treatment.

How erythropoietin is given

Erythropoietin is given as an injection under the skin (subcutaneously). It is usually given in your thigh or tummy area. You, or someone who looks after you, may be shown how to give the injections. Or they can be given by a nurse that sees you at home or at the GP surgery.

Your doctor or nurse will explain how often you need the injections. 

Storing erythropoietin

Erythropoietin should be stored in the fridge in its original packaging. Take the injection out of the fridge 30 minutes before you have it, so it can come up to room temperature.

Always follow the storage advice given by your pharmacist.

Your course of treatment

You will have regular blood tests to check how you are responding to treatment. These tests will measure your level of red blood cells and haemoglobin (Hb). Your doctor may change the dose of erythropoietin depending on these results.

If blood tests show the treatment is working, you usually continue having injections until 1 month after you finish your course of chemotherapy. Or you may continue until you are no longer anaemic.

During treatment, your doctor may also give you iron tablets or injections. Your body needs iron to make red blood cells. Your doctor can tell you if this will be helpful for you.

Your nurse, pharmacist or doctor will discuss your treatment plan with you.

About side effects

When you have erythropoietin injections, the amount of the protein in your body becomes much higher than normal. This may cause side effects, but these are usually mild or moderate.

We explain the most common side effects of this treatment here. We also include some less common side effects.

You may get some of the side effects we mention, but you are unlikely to get all of them. If you are also having treatment with other cancer drugs, you may have some side effects that we have not listed here. If you have chemotherapy with erythropoietin, some side effects may be worse. We have more information about chemotherapy. Always tell your doctor, nurse or pharmacist about any side effects you have.

Your doctor can give you drugs to help control some side effects. It is important to take them exactly as your nurse or pharmacist explains. This means they will be more likely to work for you. Your nurse will give you advice about managing your side effects. After your treatment is over, most side effects start to improve. 

Serious and life-threatening side effects

Some cancer treatments can cause serious side effects. Sometimes, these may be life-threatening. Your doctor, nurse or pharmacist can explain the risk of these side effects to you.

Contact the hospital

Your doctor, nurse or pharmacist will give you 24-hour contact numbers for the hospital. If you feel unwell or need advice, you can call at any time of the day or night. Save these numbers in your phone or keep them somewhere safe.

Side effects when treatment is being given

Skin irritation at the injection site

Your skin may become red or tender where the injection is given. Injecting into a different area of skin each time can help reduce skin irritation.

Allergic reaction

Some people have an allergic reaction while having this treatment. Signs of a reaction can include: 

  • feeling hot or flushed 
  • shivering
  • itching
  • a skin rash
  • feeling dizzy or sick
  • a headache
  • feeling breathless or wheezy
  • swelling of your face or mouth
  • pain in your back, tummy or chest. 

Your nurse will check you for signs of a reaction during your treatment. If you feel unwell or have any of these signs, tell them straight away. If you do have a reaction, they can treat it quickly. 

Sometimes a reaction happens a few hours after treatment. If you develop any of these signs or feel unwell after you get home, contact the hospital straight away on the 24-hour number.

Possible side effects

Feeling sick

Your doctor, nurse or pharmacist will prescribe anti-sickness drugs to help prevent or control sickness. Take the drugs exactly as they tell you to, even if you do not feel sick. It is easier to prevent sickness than to treat it after it has started.

If you feel sick, take small sips of fluid often and eat small amounts regularly. It is important to drink enough fluids. If you continue to feel sick, or if you are sick (vomit) 1 to 2 times in 24 hours, contact the hospital on the 24-hour number as soon as possible. They will give you advice. They may change your anti-sickness treatment. Let them know if you still feel sick.


This treatment may cause diarrhoea. Diarrhoea means passing more stools (poo) than is normal for you, or having watery or loose stools. You may also have stomach cramps. If you have a stoma, it may be more active than usual. 

If you are passing loose stools 3 or more times a day and this is not normal for you, contact the hospital as soon as possible on the 24-hour number. Follow the advice they give you about:

  • taking anti-diarrhoea medicines 
  • drinking enough fluids to keep you hydrated and to replace lost salts and minerals
  • any changes to your diet that might help. 

They might also ask you for a specimen of your stool to check for infection.

Blood clot risk

Cancer and some cancer treatments can increase the risk of a blood clot. Erythropoietin can also increase the risk of developing a blood clot. Symptoms of a blood clot include: 

  • throbbing pain, redness or swelling in a leg or arm
  • suddenly feeling breathless or coughing
  • sharp chest pain, which may be worse when you cough or take a deep breath. 

you have any of these symptoms, contact the hospital straight away on the 24-hour contact number you have been given. If you cannot get through to your doctor, call the NHS urgent advice number on 111.

A blood clot is serious, but it can be treated with drugs that thin the blood (anticoagulants). Your doctor or nurse can give you more information. 

You can help reduce the risk of developing a blood clot by:

  • staying active during treatment
  • drinking plenty of fluids, especially water.

You may be given anticoagulants to help prevent a clot.


This treatment may cause headaches. If you have headaches, tell your doctor, nurse or pharmacist. They can give you advice about painkillers that may help. Tell them if the headache does not get better, or gets worse.

High blood pressure

Erythropoietin may cause high blood pressure. Tell your doctor or nurse if you have ever had any problems with your blood pressure. You should also tell them if you take any medication for high blood pressure. Your nurse will check your blood pressure regularly during your treatment. 

Signs that your blood pressure may be very high include: 

  • a severe headache
  • feel drowsy or confused
  • problems with your eyesight
  • fits (seizures)
  • being sick (vomiting)

If you have any of these symptoms, contact the hospital straight away on the 24-hour contact number you have been given. If you cannot get through to your doctor, call the NHS urgent advice number on 111.

Muscle or joint pain

You may get pain in your muscles or joints for a few days after treatment. If this happens, tell your doctor, nurse or pharmacist. They can give you painkillers and advice. They can also tell you if any of the painkillers you usually take are suitable. 

Tell them if the pain does not get better. Having warm baths and resting regularly may help. 

Flu-like symptoms

Some people have flu-like symptoms, such as: 

  • feeling sick
  • joint pains
  • weakness
  • dizziness
  • tiredness. 

You are more likely to have these symptoms at the start of your treatment. Usually, they last for a few days. Your doctor may advise you to take paracetamol to help with these symptoms.


This treatment may cause a cough. Tell your doctor or nurse if you notice this. They may suggest treatments to help.


Erythropoietin may increase the risk of a mini-stroke or stroke, but this is not common. Contact a doctor or go to the hospital straight away if you or someone else notices: 

  • you are confused 
  • you have difficulty speaking
  • your face drooping
  • numbness or weakness on one side of your body.

Fluid build-up

Your ankles, feet or fingers may swell because of fluid building up. Tell your doctor or nurse if this happens. If your feet and ankles swell, it can help to rest your legs on a foot stool or cushion. 

Skin rash

You may develop a rash, which may be itchy and red. Tell your doctor if you notice this. They can give you advice and may prescribe creams or medicines to help.

Rarely, people develop more serious skin reactions. These can include:

  • a target-like rash (round red patches with an inner circle or blister inside)
  • blisters on the skin
  • ulcers in the mouth or in other parts of the body
  • sore, red eyes
  • becoming sensitive to the sun or artificial light. 

If you develop any of these, or have a skin rash and feel unwell or have dark coloured pee (urine), stop taking erythropoietin. Contact a doctor straight away.

Other information

Because this treatment is a growth factor, it is thought that it may cause cancer to progress in some people. Your doctor will consider the benefits and risks of this treatment before deciding whether it is suitable for you. Your doctor will talk to you about this. If you have any concerns or questions, always talk to your doctor or nurse. 

Other medicines

Some medicines can affect how this treatment works or be harmful while you are having it. Always tell your cancer doctor, nurse or pharmacist about any drugs you are taking or planning to take, such as: 


Your doctor, nurse or pharmacist will advise you not to get pregnant or make someone pregnant while having this treatment and for some time afterwards. The drugs may harm a developing baby. It is important to use contraception to prevent pregnancy. Follow their advice about:

  • what types of contraception to use 
  • how long after treatment you should continue to use contraception. 


You are advised not to breastfeed while having this treatment, or for some time after treatment ends. This is because the drugs could be passed to the baby through breast milk. 

Your doctor, nurse or pharmacist can give you more information.

Medical and dental treatment

If you need medical treatment for any reason other than cancer, always tell the healthcare professional that you are having cancer treatment. Give them the contact details for your cancer doctor or cancer team so they can ask for advice.

If you have appointments with a dentist, always tell them you are having cancer treatment. Talk to your cancer team before you have any dental treatment.

About our information

  • Reviewers

    This information has been written, revised and edited by Macmillan Cancer Support’s Cancer Information Development team. It has been reviewed by expert health professionals and people living with cancer.

    Our cancer information has been awarded the PIF TICK. Created by the Patient Information Forum, this quality mark shows we meet PIF’s 10 criteria for trustworthy health information.

The language we use

We want everyone affected by cancer to feel our information is written for them.

We want our information to be as clear as possible. To do this, we try to:

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We use gender-inclusive language and talk to our readers as ‘you’ so that everyone feels included. Where clinically necessary we use the terms ‘men’ and ‘women’ or ‘male’ and ‘female’. For example, we do so when talking about parts of the body or mentioning statistics or research about who is affected.

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Date reviewed

Reviewed: 01 December 2022
Next review: 01 June 2025
Trusted Information Creator - Patient Information Forum
Trusted Information Creator - Patient Information Forum

Our cancer information meets the PIF TICK quality mark.

This means it is easy to use, up-to-date and based on the latest evidence. Learn more about how we produce our information.