What is polycythaemia vera (PV)?

Polycythaemia vera (PV) is a type of blood cancer that affects the bone marrow. Bone marrow is where blood cells are made. 

In PV, the body makes too many red blood cells. This can make the blood thicker than normal. Some people with PV also have too many white blood cells and platelets in their blood.

Having too many red blood cells increases the risk of unwanted blood clots.

PV can happen at any age, but it is more common in people aged over 40. It is slightly more common in men. PV develops slowly – for most people, it will not shorten their lives.

To understand PV and its treatment, it can help to know more about the blood and bone marrow.

Symptoms of polycythaemia vera (PV)

Having a high number of red blood cells does not always cause symptoms. Some people are diagnosed with PV after they have a blood test for another reason.

Possible symptoms of PV include:

  • severe, migraine-type headaches
  • changes in vision
  • feeling very tired (fatigue)
  • feeling dizzy
  • itchy skin (often after a warm bath or shower)
  • sweating more than usual
  • burning pain, change in feeling, or redness in the hands or feet
  • cold or blue fingers or toes
  • redness of the face
  • bone or joint pain
  • unexplained weight loss
  • high temperature (fevers) and drenching night sweats requiring a change of clothes or bed covers
  • discomfort in the tummy area (abdomen)
  • feeling full soon after beginning to eat.

Possible complications of polycythaemia vera (PV)

Some people also develop symptoms because of complications of PV.

Enlarged spleen

The spleen sits on the left side of the tummy, just under the ribs. It is usually about the size of a fist.

The spleen
Image: The spleen

The spleen:

  • helps fight infection
  • stores and breaks down blood cells.

PV can cause the spleen to grow bigger than normal. This is called an enlarged spleen. Sometimes, this causes symptoms. These include discomfort on the left side of the tummy and feeling full quickly when eating.

Having an enlarged spleen can cause problems. It may:

  • keep blood cells in the spleen instead of releasing them into the blood
  • destroy blood cells.

Both these changes can reduce the number of blood cells in the blood.

Blood clots

Some people with PV have a higher 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.

If you have any of these symptoms, contact the hospital straight away. If you cannot speak 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 (anti-coagulants). Your doctor or nurse can give you more information.

You may be given drugs to help prevent a clot.

Blood clots can also cause heart attacks and strokes. If you think you may be having a heart attack or stroke, call 999 for an ambulance or go straight to A&E (emergency department).


When the body tries to break down (get rid of) more blood cells than usual, it can cause a painful condition called gout. Gout affects the joints. It causes pain, heat, redness and swelling. It usually only affects the big toe joint. But it can affect other joints.

Gout is caused by uric acid building up in the blood. Uric acid is produced when lots of cells are broken down. The uric acid forms crystals that get into the joint and cause the symptoms.

Usually, the kidneys can clear uric acid from the blood and pass it out of the body in the pee (urine). But sometimes, they cannot cope with large amounts.

Your doctor can check the level of uric acid in the blood. Depending on the result, they may give you a tablet called allopurinol to help prevent gout.

Bleeding or bruising

Sometimes, PV can cause abnormal bleeding or bruising. Any bleeding might be heavier than normal and take longer to stop.

Symptoms may include:

  • nosebleeds
  • bleeding gums
  • heavy periods
  • blood in your pee or stools (poo)
  • very dark poo blood in your vomit (sick) – this can be a bright red liquid or look like brown or black coffee granules
  • tiny red or purple spots on your skin that may look like a rash.

Tell your doctor if you notice any signs of abnormal bleeding or bruising.

If you think you see blood in your sick or poo, or if you have dark poo, or if any bleeding is heavy or will not stop, contact a doctor urgently. If you cannot speak to a doctor, call 999 for an ambulance or go straight to A&E.

Myelofibrosis (MF)

A very small number of people with PV may develop a more serious condition called myelofibrosis (MF). MF causes scarring of the bone marrow.

Acute myeloid leukaemia (AML)

Rarely, PV can cause a cancer of the blood cells called acute myeloid leukaemia (AML). Not everyone with PV has the same risk of developing AML.

For most people, PV remains stable for many years and does not affect how long they live for. Your doctor can tell you more about this.

Diagnosis of polycythaemia vera (PV)

Your GP might suspect you have PV if you have a raised number of blood cells in your blood over a period of time. This can be measured in a blood test called a full blood count (FBC).

Depending on your symptoms, your doctor may be able to diagnose PV straight away. Or they may need to do tests to rule out other conditions.

If your doctor thinks you may have PV, they will refer you to the hospital to see a specialist blood doctor called a haematologist. At your hospital appointment, you may also meet a clinical nurse specialist. They may be your key worker. This means they are your main contact for information and support.

Your haematologist will decide whether you need further tests. This can include more blood tests and a bone marrow biopsy

  • Genetic tests

    Genes carry the instructions that cells in the body need to work properly. There are genes that control how many blood cells are made in the bone marrow. Genes can develop changes over time. Genetic changes do not always cause problems, but they can cause conditions such as PV.

    A gene called JAK2 helps control how many blood cells the bone marrow makes. About 95 out of 100 people with PV (95%) have a change in the JAK2 gene. You can have a blood test to check for this genetic change. Most people are not born with changes in the JAK2 gene and do not pass it on to their family.

  • Blood volume test

    You may have a test to look at the amount of red blood cells and plasma cells in your blood. This is called a red cell mass test and plasma volume study.

    For this test, you have a blood sample taken. This sample is split into red blood cells and plasma cells. Both samples have a small amount of radioactivity added to them. Then they are injected back into your vein.

    You then have another blood test around 30 minutes later. The radioactivity leaves your body very quickly and it will not make you feel unwell.

  • Other blood tests

    As well as blood tests to check your general health, you may have blood tests to check:

    • the levels of iron and vitamin B12 in your blood
    • whether you make too much of a hormone called erythropoietin, which encourages red blood cells to be made.

  • Pulse oximetry

    You may have a test to measure the oxygen level in your blood. A probe is placed on your fingertip with a light that shines through your fingernail.

  • Ultrasound scan

    Sometimes your spleen gets bigger when you have PV. Your doctor may be able to feel this by examining your tummy. Or you may have an ultrasound scan.

  • Bone marrow biopsy

    Your doctor may want to take a sample of bone marrow to look at under a microscope. This is called a bone marrow biopsy. Doctors usually remove the sample from the back of the hip bone (pelvis).

    The sample is sent to a laboratory to be checked for abnormal cells.

Waiting for test results can be a difficult time. It may help to talk to your family mermbers, friends or your clinical nurse specialist.

Treatment for polycythaemia vera (PV)

Before treatment, a team of health professionals work together to plan the treatment they feel is best for you. This team is called a multi-disciplinary team (MDT).

The MDT look at the risk of you developing problems from PV. They also look at your test results and general health. They will describe the PV as low, intermediate (medium) or high risk based on:

  • your age
  • your symptoms
  • your medical conditions
  • your number of blood cells
  • whether you have genetic changes
  • the thickness of your blood (haematocrit level)
  • whether you have had blood clots.

Treatment for PV is usually given to prevent problems such as blood clots. This is called supportive treatment. Treatment can also be given to control PV by reducing the number of red blood cells (cytoreductive therapy). You will have regular blood tests to check for changes in your condition.

You and your doctors will talk about your treatment options and the possible risks and benefits before you agree (consent) to have treatment.

You may be offered treatment as part of a clinical trial.

Preventing blood clots

If you have PV, you have a higher risk of blood clots. Blood clots can cause heart attacks and strokes. It is important to reduce your risk as much as possible.

It is important that other conditions that can also increase your risk of heart attacks and strokes are managed. This includes conditions such as:

  • diabetes
  • high blood pressure
  • high cholesterol.

Lifestyle changes

Your doctors and nurses will give you advice about any lifestyle changes you can make to help reduce your risk. They usually advise you to:


Most people with PV are treated with aspirin tablets. Aspirin affects the way platelets stick together and helps prevent blood clots. Drugs that prevent clots are called anti-platelet drugs or blood thinners. Aspirin does not affect the number of platelets in the blood.

One of the side effects of aspirin is an increased risk of bleeding and ulcers in the stomach.

If you are taking aspirin, ask your doctor for advice about painkillers. Certain types of painkillers, such as ibuprofen, may not be suitable for you while you are taking aspirin.

If you cannot take aspirin because of medical conditions such as a stomach ulcer, you may be given another anti-platelet drug instead.

Reducing red blood cells

  • Removing blood (venesection)

    Regularly removing about a pint (500ml) of blood is a common treatment for PV. It reduces the number of red blood cells in the blood and makes the blood thinner.

    The procedure is like donating blood. A nurse puts a needle into your vein. The needle is attached to a tube and a bag. Your blood flows through the needle and tube, into the bag. When they have collected enough blood, the nurse removes the needle.

    You may have a venesection every few weeks or months until your blood thickness is at the right level.

    On the day you have your venesection, it is important to drink plenty of fluids. This helps replace the fluid that has been removed.

  • Chemotherapy

    Chemotherapy uses anti-cancer (cytotoxic) drugs to destroy cancer cells. It can be used to reduce the blood cell count in PV.

    Hydroxycarbamide (HC) is the most commonly used chemotherapy drug to treat PV. It can cause side effects, but these are generally mild.

    Taking HC for a long time can increase the risk of getting skin cancer. It is important that you protect your skin from the sun. You also need to check for any changes in your skin during and after treatment with HC. Your haematologist or clinical nurse specialist can tell you more about this.

    Rarely, the chemotherapy drug busulfan may be used if other treatments have not worked well. The side effects are like the side effects of hydroxycarbamide. If you take busulfan for a long time, it may slightly increase your risk of developing leukaemia.

    Chemotherapy is not suitable for everyone with PV. It temporarily affects the way the bone marrow works and may reduce the level of blood cells. If you have chemotherapy, your doctor will monitor you closely. They will explain the possible side effects of any chemotherapy drug they recommend for you..

  • Interferon alpha

    Interferon is a protein that is made naturally by the body. It can also be made as a drug (interferon alpha) and given as an injection under the skin (subcutaneously). It slows down how quickly the bone marrow makes blood cells..

  • Ruxolitinib (Jakavi®)

    Ruxolitinib (Jakavi®) is a targeted therapy drug called a JAK inhibitor. It targets the genes that help the abnormal blood cells in PV to grow. You take it daily as a tablet..

  • Anagrelide

    Anagrelide can be used if you have a high platelet count. You take it as a capsule. Side effects can include headaches and changes to your heart rate and rhythm. You may have tests to check your heart before you start taking anagrelide. Some research suggests that anagrelide may increase the risk of getting myelofibrosis.

  • Radioactive phosphorus (32P)

    Rarely, a treatment called radioactive phosphorus may be used. This might be when other treatments have been tried or are not suitable. You have it as an injection into a vein. It gives a dose of radiation to the bone marrow and reduces the number of blood cells being made. The effects of a single treatment can last from months to years.

    Having long-term treatment with radioactive phosphorus can increase the risk of leukaemia.

Pregnancy, fertility and polycythaemia vera (PV)

If you are planning to get pregnant or to make someone pregnant in the next few months, talk to your doctor first.

Chemotherapy and some other treatments may affect the development of an unborn baby. Doctors usually advise against getting pregnant or making someone pregnant during these treatments and for a few months after. It is important to use effective contraception.

Chemotherapy may affect fertility. If this is a concern for you, talk to your doctor before starting treatment.

If you are planning to get pregnant, PV can increase the risks of complications during pregnancy. But with risk-reducing treatments and careful monitoring during pregnancy, most babies are born healthy. Your haematologist and obstetrician (doctor who specialises in pregnancy) will work together to give you the best care during your pregnancy.

During pregnancy, your doctor usually advises you to take aspirin daily. This reduces the risk of complications from blood clots for both you and the baby. If you need other treatment to reduce your risk of complications, your doctor may advise having interferon.

Living with polycythaemia vera (PV)

If you have PV, you need regular check-ups and blood tests. If you are worried or notice any new symptoms between appointments, tell your haematologist or clinical nurse specialist as soon as possible.

Making lifestyle changes to reduce your risk of complications can sometimes be challenging. You may find it easier to make changes as part of a group or with help from others. If you find it hard to make changes, tell your GP, practice nurse or haematology team. There is lots of support available to help you live a healthier lifestyle.

Your feelings

Everyone has their own way of dealing with the different feelings they experience. You may find it helpful to talk about things with family members, friends, or your specialist doctor or nurse.

Macmillan is also here to support you. If you would like to talk, you can:

The organisations below also offer information and support:

  • MPN Voice

    MPN Voice is a support network for people with myeloproliferative neoplasms (MPNs). It provides information and support.

  • Leukaemia Care

    Leukaemia Care is a national blood cancer support charity for people with leukaemia and other blood disorders. It has regional support groups.

  • Blood Cancer UK 

    Blood Cancer UK is a blood cancer research charity that provides information and support on any type of blood cancer.

About our information

  • References

    Below is a sample of the sources used in our polycythaemia vera (PV) information. If you would like more information about the sources we use, please contact us at cancerinformationteam@macmillan.org.uk

    Pan-London Haemato-Oncology Clinical Guidelines Acute Leukaemias and Myeloid Neoplasms Part 4: Myeloproliferative Neoplasms. January 2020. Available from www.rmpartners.nhs.uk/wp-content/uploads/2020/01/Pan-London-MPN-Guidelines-Jan-2020.pdf (accessed July 2022).

    McMullin MF, Harrison CN, Ali S, Cargo C, Chen F, Ewing J, Garg M, Godfrey A, Knapper S, McLornan DP, Nangalia J, Sekhar M, Wadelin F, Mead AJ, on behalf of the BSH Committee. A guideline for the diagnosis and management of polycythaemia vera. 2018. A British Society for Haematology Guideline. Available from www.doi.org/10.1111/bjh.15648 (accessed July 2022).

  • Reviewers

    This information has been written, revised and edited by Macmillan Cancer Support’s Cancer Information Development team. It has been reviewed by expert medical and health professionals and people living with cancer. It has been approved by Senior Medical Editor, Dr Anne Parker, Consultant Haematologist.

    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:

  • use plain English
  • explain medical words
  • use short sentences
  • use illustrations to explain text
  • structure the information clearly
  • make sure important points are clear.

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.

You can read more about how we produce our information here.

Date reviewed

Reviewed: 01 March 2023
Next review: 01 March 2026
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.