Polycythemia vera (PV)

What is polycythemia vera?

Research‑backed patient education is central to MPN Research Foundation’s mission. People living with polycythemia vera (PV) and other myeloproliferative neoplasms (MPNs) deserve clear, accurate information they can trust to understand their diagnosis, symptoms, and treatment options.

What you’ll find inside:

Short animated explainers that break down complex topics in minutes
Expert‑led FAQ videos answering common patient questions
Patient experience stories that reflect real‑world challenges and insights

Watch the You and MPN: An Animated Patient’s Guide – Polycythemia Vera Module to learn more about this diagnosis.

Understanding and Diagnosing Polycythemia Vera (PV)

Blood flowing through your body contains several different kinds of cells. Red blood cells deliver oxygen to your tissues, white blood cells protect against infections, and platelets form clots to stop bleeding when needed. Your bones contain spongy tissue called bone marrow, where all these blood cells are created. The bone marrow functions like a factory, making the right amount of each blood cell type based on instructions from your genes.

Sometimes, the bone marrow factory receives the wrong instructions and starts making too many red blood cells. This is called polycythemia vera, or PV. It’s a type of blood cancer called a myeloproliferative neoplasm, or MPN. The name “polycythemia vera” tells us what’s happening. “Poly” means many and “cythemia” refers to blood cells. So, polycythemia means you have too many blood cells. “Vera” means true, meaning it is the primary problem, not caused by something else.

Red blood cells carry oxygen throughout your body. But when you have too many, the blood becomes thick and sticky, like honey instead of water. This thick blood doesn’t flow well through your blood vessels. It’s harder for oxygen to get where it’s needed.¹

PV is most common in people over age 60, though it can happen at any age. Men are slightly more likely than women to develop PV. Polycythemia vera is rare. Just 1 or 2 people out of every 100,000 are diagnosed each year.^2,3

Serious complications from polycythemia vera

The thick blood caused by PV can form unwanted clots inside blood vessels. These can lead to heart attacks, strokes, or blockages in the legs. PV can also cause bleeding problems. In addition, your spleen may become enlarged as it works harder to filter the extra blood cells.^1,2

What causes polycythemia vera?

PV happens because of changes in genes. The medical term for these types of changes is “mutations.” Almost all people with PV have a mutation in a gene called JAK2. The mutations signal the bone marrow to make too many red blood cells.^2,4

What are common polycythemia vera symptoms?

Many people with PV don’t feel sick at first. When PV does cause symptoms, they can include headaches, dizziness, redness of the face or hands, and itching, especially after a warm bath or shower.

Other symptoms can include blurred vision, ringing in the ears, feeling unusually tired, or having trouble concentrating. Others may experience night sweats.^1,3

How is polycythemia vera diagnosed?

PV is often discovered during a routine blood test that shows high red blood cell counts or high hematocrit. Your regular doctor might notice this during a yearly checkup or when testing for another condition.^1,2

If your blood test shows high red blood cell counts, your doctor might refer you to a hematologist – a doctor specializing in blood disorders. They can run additional tests to determine what’s causing your high blood counts.^2-4

Before diagnosing PV, doctors need to rule out other reasons for high red blood cells. They will test for conditions including sleep apnea, lung diseases, heart problems, or problems living at high altitude.^2,4

Your hematologist will test your blood for gene mutations. They will look for the JAK2 mutation , which is present in more than 9 of every 10 people with PV. Finding this mutation helps confirm the PV diagnosis and gives doctors important information about your condition.^2,4

Doctors will measure your red blood cell count, hemoglobin and hematocrit levels. These tests show how many red blood cells you have and how thick your blood has become. They will also check your level of erythropoietin, or EPO, a hormone that controls red blood cell production. In PV, this level is usually low.^2,4

Your doctor will take a small sample of bone marrow in a procedure called a bone marrow biopsy. This helps them see what is happening inside your bone marrow “factory,” and make sure it is really PV and not another condition.^2,4

Understanding your PV diagnosis and moving forward

Getting a PV diagnosis can feel overwhelming, but many people with PV live healthy lives with proper treatment. Your care team can guide you through what this diagnosis means for you.^1,2 Once PV is diagnosed, your healthcare team will work with you to create a treatment plan that’s right for you. Understanding your condition is the first step towards managing it successfully and living well.^4,5

References

MPN Research Foundation. What is polycythemia vera? https://mpnresearchfoundation.org/polycythemia-vera-pv
Tefferi A, Barbui T. Polycythemia vera: 2024 update on diagnosis, risk-stratification, and management. Am J Hematol. 2023 Sep;98(9):1465-1487.
Thapa B, Fazal S, Parsi M, Rogers HJ. Myeloproliferative Neoplasms. [Updated 2023 Aug 8]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan–.
https://www.ncbi.nlm.nih.gov/books/NBK531464
National Comprehensive Cancer Network (NCCN). NCCN Guidelines for Patients: Myeloproliferative neoplasms. Version 2024. https://www.nccn.org/patients/guidelines/content/PDF/mpn-patient.pdf
Khoury JD, Solary E, Abla O, et al. The 5th edition of the World Health Organization Classification of Haematolymphoid Tumours: Myeloid and Histiocytic/Dendritic Neoplasms. Leukemia. 2022 Jul;36(7):1703-1719.