Polycythaemia (often called Erythrocytosis) is a blood disorder characterized by an abnormally high concentration of red blood cells. This excess makes your blood thicker than usual, making it harder to circulate through your body and increasing the risk of life-threatening blood clots.
Whether you have been told you have high haemoglobin (Hb) or are investigating a Polycythaemia Rubra Vera (PRV) diagnosis, this guide explains the symptoms, causes, and treatment options.
Because thickened blood moves slowly through small blood vessels, the signs of polycythaemia are often related to poor circulation and high cell turnover.
Headaches and Dizziness: Sluggish blood flow to the brain often causes persistent “heaviness” or lightheadedness.
Itching (Pruritus): A very specific symptom, particularly itching that worsens after a hot bath or shower.
Reddish Complexion: A noticeable “ruddy” or purple glow, most visible on the face, hands, and feet (known as plethora).
Blurred Vision: You may see “spots” or experience temporary blurred vision due to thickened blood in the retinal vessels.
Fatigue: Feeling generally tired, weak, or “sluggish” despite getting enough sleep.
Tinnitus: A persistent ringing or buzzing in the ears.
Night Sweats: Excessive sweating during the night, often associated with primary polycythaemia.
Painful Swelling of Joints: High red cell turnover can lead to gout, causing painful, swollen joints (usually the big toe).
Fullness in the Abdomen: Caused by an enlarged spleen (splenomegaly) as it works overtime to filter excess blood cells.
High Blood Pressure: The heart must pump harder to move the thickened blood through the arteries.
Polycythaemia increases the risk of blood clots, which can be fatal if not treated. Seek emergency medical care (call 999 or go to A&E) if you experience:
Signs of a Stroke: Facial drooping, arm weakness, or slurred speech.
Signs of a Blood Clot (DVT): Pain, swelling, redness, and warmth in one leg.
Signs of a Pulmonary Embolism: Sudden shortness of breath or sharp chest pain.
Signs of a Heart Attack: Pressure, tightness, or squeezing in the chest.
The treatment for polycythaemia depends entirely on why your body is overproducing cells.
Primary Polycythaemia (Polycythaemia Rubra Vera, PRV)
This is a rare, chronic blood cancer. A genetic mutation (usually in the JAK2 gene) signals your bone marrow to produce red blood cells uncontrollably. It is a long-term condition that requires specialist haematology care.
Secondary Polycythaemia
This is more common and is usually a “reaction” to another factor. Common triggers include:
Smoking: Carbon monoxide in smoke reduces oxygen, forcing the body to make more red cells.
Lung Disease (COPD) or Sleep Apnoea: Low oxygen levels trigger a survival response to produce more oxygen carriers.
Living at High Altitude: The thin air naturally increases red cell counts.
Dehydration: This causes “apparent” polycythaemia; the blood is concentrated because there is less fluid (plasma), not necessarily more cells.
Doctors use a systematic approach to confirm a diagnosis:
Full Blood Count (FBC): Measures levels of haemoglobin and haematocrit (the percentage of your blood made of red cells).
JAK2 Genetic Test: A specialized blood test to look for the mutation that confirms Polycythaemia Vera.
Erythropoietin (EPO) Level: EPO is a hormone that stimulates cell production. Levels are usually low in PV but high in secondary types.
Oxygen Saturation: To determine if a lung condition is the underlying cause.
The primary goal of treatment is to reduce blood “thickness” (viscosity) and prevent clots.
Venesection (Phlebotomy): The most common treatment. A pint of blood is removed—similar to a blood donation—to quickly lower the red cell count.
Low-Dose Aspirin: Prescribed to make blood “slippery” and reduce the risk of clotting.
Cytoreductive Therapy: Medications like Hydroxycarbamide may be used to slow down cell production in the bone marrow.
Lifestyle Changes: Quitting smoking is essential for managing secondary polycythaemia.
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