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Polycythaemia vera explained | CION Cancer Clinics
Polycythaemia vera is a long-term blood cancer in which the bone marrow makes too many red blood cells, so the blood thickens and clots become more likely. It usually moves slowly. Most people carry a JAK2 gene change, and treatment with venesection, aspirin and sometimes tablets aims to keep the blood thin. This page explains the signs, the tests and what the diagnosis does and does not mean. At CION Cancer Clinics, every leukaemia, MDS and MPN case is reviewed by our haematologist and discussed at a tumour board before a plan is agreed.
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Medically reviewed by Dr. Basudev PokhrelConsultant Haematologist · last reviewed September 2026, next review due September 2027
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On this page
- What is polycythaemia vera, in plain words?
- What signs does polycythaemia vera cause?
- How does a haematologist confirm it?
- What do the words on the report mean?
- How is polycythaemia vera treated?
- What do families often get wrong about it?
- What can this page not tell you?
- Common questions about polycythaemia vera
The short answer
What is polycythaemia vera, in plain words?
Polycythaemia vera is a long-term blood condition where the bone marrow makes too many red blood cells. The blood becomes thicker than it should be, and thick blood raises the chance of a clot.
Why it is called a blood cancer
It belongs to a group called myeloproliferative neoplasms, or MPNs. The word neoplasm means the marrow cells have changed and keep growing on their own. That is why it is looked after by a haematologist and listed among blood cancers. For most people it behaves very differently from the leukaemia families usually picture. It tends to move slowly, over many years, and many people live ordinary working lives with it.
What causes it
In most people a change in a gene called JAK2 is found in the blood cells. This change happens during life. It is not passed down from a parent in the usual way, and nothing you ate or did is known to have caused it.
Why finding it matters
The main danger is not the extra cells themselves. It is the clots they make more likely, in the legs, lungs, heart or brain. Treatment is built around lowering that risk.
A single high haemoglobin on a report is not a diagnosis. Many common things push haemoglobin up, and those are checked first.What people notice
What signs does polycythaemia vera cause?
Many people have none at all. The condition is often found on a routine blood test done for something else.
Itching after a bath
A prickly, intense itch that starts after a warm bath or shower, with no rash to see. It is one of the more typical early clues and is often put down to soap or dry skin for years.
Headache and a red face
Thick blood moves more slowly. Some people notice headaches, dizziness, a flushed face, blurred vision or ringing in the ears.
Burning hands or feet
Redness, warmth and burning pain in the fingers or toes, often worse in heat. It comes from small vessels being blocked by sticky blood.
A full feeling on the left
The spleen can grow larger. You may feel full after a small meal or notice a dragging discomfort under the left ribs.
Also reported
- Tiredness and night sweats
- Gout or joint pain
- Easy bruising or gum bleeding
Not sure whether this applies to you?
Ask an oncologistConfirming it
How does a haematologist confirm it?
Repeat the count
A full blood count is repeated, because a single result can be thrown off by dehydration or a laboratory difference. The haemoglobin and the haematocrit are the key numbers.
Look for other causes
Smoking, sleep apnoea, lung or heart disease, kidney problems and testosterone use all raise red cells. These are checked before anyone labels the marrow as the cause.
The JAK2 blood test
A gene test on an ordinary blood sample. A positive result, together with a raised count, points strongly towards polycythaemia vera. A level of a hormone called erythropoietin is often checked too.
Sometimes a marrow sample
A bone marrow biopsy, a small sample taken from the hip bone, is not always needed. It helps when the picture is unclear or other counts are also raised.
On your report
What do the words on the report mean?
- Haematocrit (HCT or PCV)
- The share of your blood made up of red cells. It is the number most treatment decisions follow.
- JAK2 V617F
- The name of the gene change most often found. "Detected" means it is present in the blood cells.
- Erythropoietin (EPO)
- A hormone from the kidneys that tells the marrow to make red cells. It is usually low or normal in polycythaemia vera.
- Splenomegaly
- An enlarged spleen, found on examination or on an ultrasound.
- MPN
- Myeloproliferative neoplasm, the family of marrow conditions this belongs to.
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Treatment
How is polycythaemia vera treated?
Treatment aims to keep the blood thin enough to lower the risk of a clot, and to ease symptoms. It is usually long term and adjusted over the years rather than given as a single course.
Removing blood
Venesection is the first step for most people. Blood is taken from a vein, much like a blood donation, to bring the haematocrit down. Most guidelines aim to keep it below 45%, although your haematologist sets your own target.
Aspirin
Low-dose aspirin is often added to make platelets less sticky. It does not suit people with certain bleeding problems or very high platelet counts, so your team decides whether it is right for you.
Medicines that slow the marrow
People at higher risk of a clot, usually those over 60 or who have already had one, may be offered a medicine such as hydroxyurea or interferon. Newer targeted medicines like ruxolitinib are used when those do not work or are not tolerated.
Never start, stop or change any of these on your own. The treating team sets and reviews every medicine.Commonly believed
What do families often get wrong about it?
"Too much blood means strong health."
A high haemoglobin is often praised as a sign of good health. In polycythaemia vera it is the problem. Thick blood clots more easily, so the extra red cells need bringing down, not celebrating.
"It is cancer, so chemotherapy will start at once."
Many people are managed for years with venesection and aspirin alone. Tablets that calm the marrow are added only when the risk profile calls for them, and they are very different from hospital chemotherapy.
"Drinking more water will fix the count."
Staying well hydrated is sensible and can stop a dehydrated sample from looking worse. It does not change what the marrow is making, so it cannot replace the treatment your haematologist plans.
"Once the count is normal, treatment can stop."
A normal count usually means the treatment is working. Stopping on your own lets the count climb back quietly, often with no warning signs until a clot happens.
Being straight with you
What can this page not tell you?
This page cannot tell you whether you have polycythaemia vera, or what it means for you. Reference ranges differ between laboratories, and a single result is always read alongside your symptoms and repeat tests.
It cannot give you your outlook
How the condition behaves depends on your age, whether you have had a clot, your other health conditions, how your counts respond and, over many years, whether the marrow changes. A small number of people later develop scarring of the marrow or, more rarely, acute leukaemia. Your haematologist is the right person to explain your own picture.
What you can do now
Keep a copy of every blood report in one folder, with dates. Stop smoking, because it thickens the blood further. Stay active, and control blood pressure, sugar and cholesterol, since these add to clot risk. At CION, the haematology team reviews the full picture, discusses it at a tumour board and coordinates any specialist tests with qualified centres.
Sudden weakness on one side, chest pain, breathlessness or a painful swollen leg needs emergency care. Call 108 or go to the nearest emergency department.Questions we are asked
Common questions about polycythaemia vera
Is polycythaemia vera a cancer?
It is classed as a chronic blood cancer because the marrow cells have changed and grow on their own. In practice it usually behaves as a long-term condition that is managed rather than a fast-moving illness. Many people carry on working, travelling and raising families while it is controlled with regular checks.
Can polycythaemia vera go away?
Current treatment controls it rather than removing it. The aim is to keep the blood thin, reduce clots and ease symptoms for as long as possible. Treatment is reviewed through the years, and the plan changes if the counts or your circumstances change. Your haematologist will explain what control looks like for you.
Will my children get it?
The JAK2 change develops during life in the marrow cells, so it is not usually inherited. Some families do show a slightly higher tendency to MPNs, but routine testing of children with no symptoms is not normally advised. Mention any relatives with blood conditions to your haematologist, who can say whether anything further is sensible.
How often will I need blood tests?
At the start, fairly often, while venesection brings the haematocrit down and the team learns how your body responds. Once things are steady, the gap between checks usually lengthens. The exact schedule depends on your treatment and counts, so follow the plan your own team gives you rather than a general rule.
Can I donate blood instead of having venesection?
Usually not. Blood banks generally do not accept blood from people with a blood cancer, and venesection is timed and measured against your own target. It is done under medical supervision so the team can track your haematocrit and iron. Ask your haematologist before approaching any blood bank.
Does diet make a difference?
No food lowers red cells. A balanced diet, enough water, less salt and keeping weight, blood pressure and sugar under control all help reduce clot risk. Do not take iron tablets unless your haematologist advises it, because iron can push red cell production back up after venesection.
Can I travel or fly with it?
Most people can, once the counts are controlled. On long journeys, walk about, drink water and avoid sitting still for hours, because clots are more likely when blood moves slowly. If a trip or surgery is planned, tell your haematologist early so any extra precautions can be arranged in advance.
Is treatment covered by Aarogyasri or insurance?
Coverage depends on the scheme, your card and the specific test or medicine. Aarogyasri, CGHS, ECHS, EHS, PM-JAY and cashless insurance may each treat long-term blood conditions differently, and the rules change. Call the helpline with your card details and the team will help you check your current cover.
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Dr. Basudev Pokhrel reviews blood counts, transfusion needs and blood disorders, and works with the CION tumour board on blood cancers.
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Sources
- National Heart, Lung, and Blood Institute — Polycythemia vera
- Leukemia & Lymphoma Society — Polycythemia vera
- NHS — Polycythaemia
- National Health Mission — National Health Mission
This page is general information, not a prescription. Do not change or stop any treatment based on what you read here. If anything is worrying you, contact your own treating team — or call our helpline and we will help you reach the right specialist.
Keep reading
Related pages
JAK2 Mutation Testing: What a Positive MeansWhat the gene test result on your report saysVenesection: Why Blood Is Removed as TreatmentWhat happens at the first and later sessionsHaematocrit Targets in Polycythaemia VeraThe number your treatment is steered byHigh Haemoglobin: Primary or SecondaryThe common causes checked before a marrow diagnosis
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