Polycythemia: A Comprehensive Guide
Medically reviewed by Andre Stone | MD, University of Pittsburgh School of Medicine on August 24th, 2026.
Published on April 7th, 2026. Updated on August 28th, 2026.
Key Takeaways
Polycythemia, also called erythrocytosis, means that red blood cells are unusually concentrated in your blood. This may happen because your body makes too many red blood cells or because the liquid portion of your blood is reduced.
Two main types exist: primary (caused by genetic mutations) and secondary (caused by other conditions like low oxygen levels)
Common symptoms include headaches, dizziness, fatigue, and increased risk of blood clots
Treatment focuses on reducing red blood cell count through blood removal, medications, or addressing underlying causes
Early diagnosis and proper management can prevent serious complications like stroke or heart attack
Overview
Polycythemia, or erythrocytosis, refers to an unusually high concentration of red blood cells. This can result from increased red blood cell production or a reduction in the liquid portion of the blood. When you have this condition, your blood becomes thicker and more viscous than normal. This makes it harder for blood to flow through your vessels and increases your risk of serious complications.
Polycythemia vera is rare, and estimates of how often it occurs vary. Other forms of erythrocytosis have different frequencies depending on their cause. It can happen at any age but is most common in adults over 60. Men and women are affected equally, though some types may be slightly more common in men.
Understanding polycythemia is important because untreated cases can lead to dangerous blood clots, stroke, or heart problems. With proper diagnosis and treatment, most people with polycythemia can live normal, healthy lives. Your doctors can help you manage your blood cell production and keep you healthy. Understanding rare types of anemia and other blood disorders helps provide context for how polycythemia differs from conditions that cause too few red blood cells.
Symptoms & Signs
Polycythemia symptoms develop gradually as your red blood cell count increases. Many people don't notice symptoms at first because the changes happen slowly over time. Some symptoms may feel like other common health problems, so it's important to talk with your doctor.
Primary Symptoms
Headaches and dizziness - Thick blood doesn't flow as easily to your brain, causing frequent headaches and feeling lightheaded
Fatigue and weakness - Despite having more red blood cells, you may feel tired because thick blood is harder to pump
Shortness of breath - Your heart works harder to move thick blood, making you feel breathless during normal activities
Itching after warm baths or showers - This unusual symptom affects many people with polycythemia and may be related to increased blood flow
When to Seek Care
Watch for signs that your condition may be getting worse or causing complications. Chest pain, severe headaches, or sudden vision changes need immediate attention. Swelling in your legs or arms could signal blood clots forming. Pain or numbness in your hands and feet may also indicate your condition needs medical attention.
When to Seek Immediate Care
Contact emergency services for chest pain, difficulty breathing, a sudden severe headache, sudden vision changes, or signs of stroke such as weakness on one side. Contact your healthcare professional promptly about new limb swelling, pain, or numbness.
Causes & Risk Factors
Age
Most common in people over 60, though it can occur at any age
Genetics
Polycythemia vera is usually caused by an acquired mutation, most often involving JAK2. It is generally not inherited, although having an affected close relative may slightly increase risk.
Lifestyle
Smoking reduces oxygen in blood, potentially triggering secondary polycythemia
Other Conditions
Lung disease, heart defects, kidney tumors, or sleep disorders increase risk
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Diagnosis
Medical History & Physical Examination
Your doctor will ask about your symptoms, family history, and lifestyle factors. They'll want to know about any breathing problems, headaches, or unusual itching. The physical exam includes checking for an enlarged spleen, which is common in polycythemia.
Your doctor will also look for signs of thick blood like redness in your face, hands, or feet. They'll listen to your heart and lungs to check for any underlying conditions that might be causing secondary polycythemia.
Diagnostic Testing
Complete Blood Count (CBC) - Measures hemoglobin, hematocrit, red blood cells, and other blood cells. Abnormal results are usually repeated and evaluated with other tests, which may include an erythropoietin level, JAK2 testing, and tests for possible underlying causes.
Genetic Testing - Looks for specific mutations like JAK2 that cause primary polycythemia vera
Oxygen Levels - Arterial blood gas tests check if low oxygen is causing your body to make extra red blood cells
Bone Marrow Biopsy - May be needed to examine how your bone marrow is producing blood cells
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Treatment Options
Treatment goals focus on reducing your red blood cell count and preventing complications like blood clots. Your specific treatment plan depends on whether you have primary or secondary polycythemia. Your doctor will work with you to find the best approach for your situation.
Conservative Treatments
Phlebotomy (Blood Removal) - Regular blood draws reduce red blood cell count quickly and effectively, similar to blood donation
Low-Dose Aspirin - May be recommended for some people, especially those with polycythemia vera, to reduce clotting risk. Take aspirin only if your clinician recommends it because it can increase bleeding risk and is not appropriate for everyone.
Hydration - Drinking plenty of water helps thin your blood and makes it flow more easily through vessels
Advanced Treatments
Hydroxyurea - Medication that reduces bone marrow production of red blood cells when phlebotomy alone isn't enough
Interferon Therapy - Used in younger patients or when other treatments don't work effectively
JAK Inhibitors - Newer medications that target specific pathways involved in blood cell production
Living with the Condition
Daily Management Strategies
Avoid dehydration and follow your healthcare professional's advice about how much fluid to drink. Some people with heart, kidney, or other conditions may need fluid limits. Ask your healthcare team whether your condition or treatment requires any activity precautions, especially if you take medicines that increase bleeding risk. Keep regular appointments with your healthcare team to monitor your blood counts and adjust treatment as needed.
Make sure to take your medications exactly as prescribed by your doctor. Keep a diary of your symptoms to help your healthcare team understand what's working best for you. Understanding whole medical systems can provide additional support approaches. Wear compression stockings during long flights or car rides to prevent blood clots in your legs.
Exercise & Movement
Regular moderate exercise like walking, swimming, or cycling helps improve circulation and overall health. Ask your healthcare team whether you should avoid contact sports or other activities with a high risk of injury. Listen to your body and rest when you feel fatigued - this is your body's way of managing the extra work of pumping thick blood.
Exercise doesn't have to be intense to be helpful. Even 30 minutes of gentle activity most days can improve how you feel and help manage your condition.
Prevention
Quit smoking to improve oxygen levels and reduce the need for extra red blood cells
Stay hydrated with plenty of water throughout the day
Manage underlying conditions like sleep apnea or lung disease that can trigger secondary polycythemia
Follow up regularly with your healthcare provider for blood count monitoring
Avoid living at high altitudes if possible, as lower oxygen levels can worsen your condition
Get treatment quickly for any lung or heart problems to prevent them from causing secondary polycythemia
Frequently Asked Questions
Primary polycythemia vera is classified as a blood cancer, but it's usually slow-growing and manageable. Secondary erythrocytosis is not a blood cancer. It may be a response to low oxygen, but it can also result from certain medicines, excess erythropoietin production, or other conditions.
Secondary erythrocytosis may improve when its underlying cause can be identified and successfully treated, although this is not always possible. Primary polycythemia vera cannot be cured but can be effectively managed with ongoing treatment and monitoring.
Initially, you may need phlebotomy weekly or monthly until your blood counts normalize. Once stable, many people need blood removal every few months, but frequency varies by individual.
Whether blood removed from a person with erythrocytosis can be donated for use by others depends on the cause, the blood center's rules, and local regulations. Ask your treatment team or blood center about eligibility. However, therapeutic phlebotomy (blood removal for treatment) serves a similar purpose for your health.
Primary polycythemia vera can have a genetic component, but most cases are not directly inherited. Understanding allergies and other conditions shows how genetic factors can influence various health conditions.
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