Polycythaemia vera (PV)

Polycythaemia vera (PV) is a rare condition affecting the bone marrow. Bone marrow is the spongy material found in bones, where our blood cells are made. In PV there are too many red blood cells, making the blood thick.

People with PV often have no symptoms. Sometimes your spleen may grow in size due to trying to break down too many red blood cells.

 PV is diagnosed using different blood tests, an ultrasound scan or a bone marrow sample. This is when a sample of bone marrow cells is taken from your back or hip bone. It will then be looked at under a microscope by a doctor.

If you have no symptoms, you may not need treatment straight away. If you do have symptoms, the main treatment for PV is venesection. This reduces the number of red blood cells by taking about a pint of blood from your body. Other treatments include:

  • chemotherapy
  • low-dose aspirin
  • interferon alpha
  • radioactive phosphorus (32P).

Once treatment has finished you will have regular blood tests and check-ups.

Bone marrow

To understand polycythaemia vera (PV) and its treatment, it can help to know more about your blood and bone marrow. Bone marrow is the spongy material found inside bones. It’s part of the immune system, which protects us from infection and disease. Stem cells are made in the bone marrow. Stem cells are blood cells at their earliest stage of development. All blood cells grow from stem cells.

The three main types of blood cells are:

  • red blood cells, which carry oxygen around the body
  • white blood cells, which fight infections
  • platelets, which help blood clot to stop bleeding.

The bone marrow makes millions of blood cells every day.

Myeloproliferative neoplasms (MPNs)

MPNs affect how the bone marrow works. The main types of MPN are:

  • polycythaemia vera (PV)
  • essential thrombocythaemia (ET)
  • myelofibrosis.

Some people with polycythaemia vera develop myelofibrosis. This is a condition where the bone marrow becomes scarred. Rarely, people with MPNs develop leukaemia.

Polycythaemia vera (PV)

PV is a rare condition that affects the bone marrow. This can lead to too many red blood cells being made, which makes the blood thicker than normal. Some people with PV also have increased numbers of white blood cells and platelets in their blood.

PV mainly affects people over the age of 40. It is twice as common in men as in women. PV develops very slowly and, for most people, it doesn't affect their normal life span.

Secondary polycythaemia

Having too many red blood cells in the blood isn’t always due to changes in the bone marrow. Some conditions, such as lung disease or a kidney disorder, can also lead to an increase in red blood cells. This is called secondary polycythaemia. 

Secondary polycythaemia can also be caused by smoking, drinking large amounts of alcohol or having high blood pressure.

The treatment of secondary polycythaemia is different from PV. It involves treating the condition that has led to the increased number of blood cells or giving advice about changing lifestyle.

Signs and symptoms of polycythaemia vera

Having a high number of red blood cells doesn't always cause symptoms. Some people are diagnosed with PV after a blood test taken for other reasons.

Possible symptoms of PV include:

  • headaches
  • blurred vision
  • tiredness
  • itchy skin
  • red skin, for example on the face, hands and feet.

Sometimes other symptoms develop, such as gout (inflammation in the joints) or blood clots.

Bleeding or bruising

Very occasionally, PV can cause abnormal bleeding. This can cause symptoms such as:

  • nosebleeds
  • bruising
  • abnormal vaginal bleeding in women
  • bleeding gums.

Enlarged spleen

The spleen sits on the left side of the tummy (abdomen) just under the ribs and is normally about the size of a fist. It helps break down red blood cells. PV can cause the spleen to grow bigger than normal. Symptoms of an enlarged spleen include discomfort on the left side of the tummy and quickly feeling full when eating.

Diagnosing polycythaemia vera

PV is usually diagnosed by a specialist in blood disorders (haematologist). The diagnosis may be suspected from the results of a routine blood test called a full blood count (FBC). This test counts the number of red blood cells, white blood cells and platelets in the blood.

Various tests and investigations may be done to confirm a diagnosis of PV. These tests will check to see if other conditions are affecting your blood counts. This may result in a diagnosis of secondary polycythaemia.

JAK2 blood test

This blood test checks for a change (mutation) in a gene called JAK2. This gene helps control how many blood cells are made. A change in the gene can cause PV. About 95 out of 100 people with PV (95%) have a mutation in the JAK2 gene. The mutation happens during the person's lifetime. It isn't something you’re born with and you can’t pass it on to your children.

Blood tests

Blood tests may be done to check:

  • the levels of iron and vitamin B12 in the blood
  • if your body is making too much erythropoietin (a hormone that encourages red blood cells to be made)
  • how much oxygen your blood is carrying (oxygen saturation test).


An ultrasound scan uses sound waves to build up a picture of internal organs, including the kidneys, liver and spleen.

Bone marrow sample (biopsy)

Your doctor may want to take a sample of marrow (biopsy) to be checked. The sample is usually taken from the back of your hip bone (pelvis). You’ll be given an injection of local anaesthetic to numb the area. The doctor will then pass a needle through the skin into the bone, and draw a small sample of liquid marrow into a syringe. This is called a bone marrow aspirate.

After this, the doctor will take a small core of marrow from the bone (a trephine biopsy). Both samples will be looked at later under a microscope.

Bone marrow sample
Bone marrow sample

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Treating polycythaemia vera

Treatment for PV aims to reduce the number of red blood cells in the blood. This will reduce symptoms and the risk of further problems such as blood clots or gout. Your treatment will depend on your full blood count, your general health and if you have symptoms. If you have been diagnosed with PV but it’s not causing you any problems, you may not need any treatment for a while.


This reduces the number of red blood cells in your blood and makes your blood thinner.

A doctor or nurse puts a needle into your vein. The needle is attached to tubing and a bag. Blood flows through the needle and tubing into the bag. When enough blood has been taken (about a pint), the needle is taken out.

Venesection may be done regularly, every few weeks or months, until your blood gets to the right level of thickness. Each time some blood is removed, you will be asked to drink plenty of fluids to replace what has been removed.

Low-dose aspirin

Having a high level of red blood cells or platelets in the blood increases the chance of blood clots (thromboses). Aspirin can help prevent clots because it affects the way platelets 'stick together'. Some people may take it as part of their treatment.

One of the side effects of aspirin is an increased risk of bleeding and ulcers in the stomach. If you need to take a painkiller while you’re taking aspirin to prevent blood clots, ask your doctor for advice. Some types of painkillers, such as ibuprofen, may not be suitable.


Chemotherapy is the use of anti-cancer (cytotoxic) drugs to destroy cancer cells. For PV, it can be used to reduce the blood cell count.

Hydroxycarbamide is the most commonly used chemotherapy drug to treat PV. It is taken by mouth as a capsule. It can cause side effects, but generally these are mild. They may include:

  • lowered resistance to infection
  • diarrhoea
  • constipation.

There is a very small risk of leukaemia developing if hydroxycarbamide is used for a long time. Patients under the age of 40 may be given other drugs instead.

Rarely, the chemotherapy drug busulfan may be used. This drug is used when other treatments have not been successful. Busulfan is usually given as a tablet. Its side effects are similar to those of hydroxycarbamide. There is also a small risk of leukaemia developing if busulfan is used for a long time.

Chemotherapy may affect fertility. People taking chemotherapy drugs are advised not to get pregnant or father a child. This is because there may be a risk of harming the developing baby. It is advisable to use contraception while taking chemotherapy drugs and for a few months afterwards.

Interferon alpha

Interferon is a natural substance made by some types of white blood cell. Man-made interferon can be given as a medicine to treat some types of cancer and leukaemia. In PV it can be used to slow down the rate at which blood cells are made. Interferon is given as an injection under the skin. Side effects can include:

  • flu-like symptoms
  • headaches
  • dizziness
  • tiredness
  • mood swings.

Radioactive phosphorus (32P)

Rarely, a treatment called radioactive phosphorus may be used. It is given as an injection. It irradiates the bone marrow and can lower the number of blood cells being produced. The effects of a single injection can last from months to years.

Long-term treatment with radioactive phosphorus can cause an increased risk of leukaemia.


Some people with PV develop gout. Gout is a painful condition that is caused by inflammation in joints such as the big toe and sometimes in the ankles, hands or knees.

Allopurinol can be used to prevent gout. It may be given before treatment that destroys blood cells, such as chemotherapy. If you have had gout, you may be prescribed allopurinol to take for the long term to prevent it happening again.

Stem cell or bone marrow transplant (from a donor)

Some people with PV may have treatment using stem cells. This treatment is not suitable for everyone. Stem cell transplant is an intensive treatment that’s used for younger people with PV that is developing into leukaemia or myelofibrosis. Myelofibrosis is disease where scar tissue builds up inside the bone marrow and blood cells aren’t made properly.

Stem cell transplant involves giving high doses of chemotherapy and then replacing stem cells (early blood cells) that have been destroyed by the treatment. After chemotherapy, you are given stem cells from a donor. This may be a sibling or volunteer who is a match for you.

Your doctor or nurse will explain your treatment to you and should answer any questions that you have.

Clinical trials

There are also some newer treatments available that may be used to help control PV. You may be invited to join a clinical trial looking at new ways of treating PV.

Clinical trials are currently studying a new drug called ruxolitinib. This drug is a type of targeted therapy called a JAK2 inhibitor. It blocks the signals that cause cells to grow and divide. The trial is for people with PV who may have a high risk of developing myelofibrosis or leukaemia. It may also be used if hydroxycarbamide is no longer helping your PV.

You can ask your haematologist whether a clinical trial may be an option for you.

Follow-up for polycythaemia vera

You’ll have regular check-ups and blood tests. If you notice any new symptoms in between appointments, you should discuss them with your doctor or haematologist as soon as possible. Symptoms to be aware of are:

  • pain or swelling in the leg
  • breathlessness
  • chest pain
  • severe headaches.

These could be signs of a blood clot.

As well as the treatments and check-ups recommended by your haematologist, you may want to look at ways of staying healthy. Following a healthy diet, drinking plenty of fluids, staying active and giving up smoking are good for your general health. This may also help reduce the risk of complications such as blood clots. Your doctor or specialist nurse can give you advice about this.

Your feelings

Everyone has their own way of dealing with their illness and the different emotions they experience. You may find it helpful to talk to family and friends or your doctor or nurse. You can also contact our cancer support specialists or these organisations for more information and support:

  • MPN Voice is a support network for people with MPNs (myeloproliferative neoplasms) providing information and support.
  • Leukaemia CARE is a national group promoting the welfare of people with leukaemia and other blood disorders. It has regional support groups in many counties.

References and thanks

This page has been compiled using information from a number of reliable sources. If you’d like further information on the sources we use, please feel free to contact us.

This information was reviewed by a medical professional. Thank you to all of the people affected by cancer who reviewed what you're reading and have helped our information to develop.

You could help us too when you join our Cancer Voices Network – find out more.

Back to Other blood cancers

Myelofibrosis (MF)

Myelofibrosis (MF) is a type of bone marrow disease. Rarely, MF leads to leukemia.

Myelodysplatic syndromes (MDS)

Myelodysplatic syndromes (MDS) are a group of conditions that affect the bone marrow. Sometimes, MDS can develop into acute leukaemia.