Polycythaemia: causes, symptoms and treatment of a high red cell count

The NHS says erythrocytosis can be divided into several types depending on the cause, and that in some cases an underlying cause cannot be identified. It is useful to think of three questions: is the blood simply more concentrated, is the bone marrow making too many red cells, or is something else telling it to?

Apparent erythrocytosis is where your red cell count is normal but you have a reduced amount of plasma in your blood, making it thicker. The NHS says this is often caused by being overweight, smoking, drinking too much alcohol or taking certain medicines, including diuretics. Relative polycythaemia is similar and can be the result of dehydration.

Absolute erythrocytosis is where the body produces too many red blood cells. The NHS describes two main types: primary, where there is a problem in the cells produced by the bone marrow that become red blood cells (the most common type is polycythaemia vera), and secondary, where an underlying condition causes more erythropoietin to be produced.

Erythropoietin is a hormone made by the kidneys that stimulates the bone marrow to make red blood cells. The NHS lists chronic obstructive pulmonary disease (COPD), where not enough oxygen reaches the body's tissues, and kidney problems such as a kidney cancer or narrowing of the arteries supplying the kidneys as examples of causes of secondary erythrocytosis.

Red blood cells carry oxygen around the body. In polycythaemia there are too many of them relative to the fluid part of the blood, so the blood is thicker. The NHS says many of the symptoms are caused by this sluggish flow of blood.

Doctors measure this with a full blood count. The NHS says it can be diagnosed by checking the number of red blood cells (the red blood cell count) and the amount of space the red cells take up in the blood (the haematocrit level), and that a high concentration suggests erythrocytosis.

Polycythaemia is a finding that needs explaining rather than a single disease. A person with a raised count because of dehydration is in a very different position from a person with polycythaemia vera, which is why a cause is always sought.

The NHS says not everyone with erythrocytosis has symptoms, but many do. It advises making an appointment with your GP if you have persistent symptoms.

• Headaches, blurred vision, dizziness and confusion.

• Red skin, particularly in the face, hands and feet (this may be more difficult to see on black or brown skin).

• Tiredness and high blood pressure.

• Discomfort in the tummy.

• Bleeding problems such as nosebleeds and bruising.

• Gout, which can cause joint pain, stiffness and swelling.

• Itchy skin, especially after a bath or shower.

Diagnosis starts with a blood test, often a routine one. The NHS says your GP may refer you to a haematologist, a specialist in blood disorders, for more tests to confirm the diagnosis and determine the underlying cause. These may include a blood test to look for the changed JAK2 gene and an ultrasound scan of your tummy to look for problems in your kidneys.

Because the cause decides the treatment, it is worth being clear about the medicines you take, whether you smoke and how much alcohol you drink, and whether you have breathing, sleep or kidney problems, so that apparent and secondary causes can be looked for before a bone marrow condition is assumed.

The NHS says treatment aims to prevent symptoms and complications such as blood clots, and to treat any underlying cause. For apparent erythrocytosis, it says that identifying and managing the cause, such as stopping smoking or reducing alcohol, may help.

Venesection is the simplest and quickest way of reducing the number of red cells. The NHS says it may be recommended if you have polycythaemia vera, a history of blood clots or symptoms suggesting your blood is too thick, and involves removing about 1 pint (half a litre) of blood at a time, in a similar way to blood donation. At first you may need it every week, and less often once the condition is under control.

In polycythaemia vera, medicines may be prescribed to slow red cell production. The NHS gives hydroxycarbamide, taken as tablets every morning and not to be taken if you are pregnant or trying to become pregnant, and interferon, injected 1 to 3 times a week, which can be taken in pregnancy but may cause side effects such as hair loss and flu-like symptoms. Daily low-dose aspirin may be prescribed to help prevent clots, and may also be offered with apparent or secondary erythrocytosis if you have another condition affecting your blood vessels, such as coronary heart disease. Some people also need treatment for itching or for an underlying cause such as COPD.

Polycythaemia is the general finding of a high red cell count. Polycythaemia vera is one specific cause. The NHS describes it as rare, usually caused by a change in the JAK2 gene that makes the bone marrow cells produce too many red blood cells, and as a slow-growing type of blood cancer. It may also cause high numbers of platelets and white blood cells. The NHS says that although caused by a genetic change, it is not usually inherited, most cases develop later in life and the average age at diagnosis is 60.

Having a high red cell count therefore does not mean you have a blood cancer. Many causes are common and manageable. If you want the specific detail on polycythaemia vera, see the dedicated guide linked below.

The NHS says erythrocytosis can cause blood clots, which put you at risk of life-threatening problems such as a pulmonary embolism and deep vein thrombosis (DVT), and increases the risk of heart attack and stroke.

Seek medical help immediately for signs of DVT or a pulmonary embolism, which the NHS lists as pain, swelling, redness and tenderness in one leg, a heavy ache in the area, warm skin, breathlessness, chest or upper back pain, coughing up blood, feeling light-headed or dizzy, or fainting. Seek emergency help if you think you or someone with you is having a heart attack or stroke.

The NHS says healthy lifestyle changes can improve some cases of apparent erythrocytosis and can also reduce the risk of blood clots in all types, since having erythrocytosis already puts you at high risk and being overweight or smoking adds to it. Its suggestions include losing weight, managing high blood pressure and stopping smoking.

MPN Voice, a UK charity for people affected by myeloproliferative neoplasms such as polycythaemia vera, provides information and support if your diagnosis is of that kind.

The usual NHS route is a GP, who repeats the blood count and may refer you to a haematologist. Treatments such as venesection and long-term medicines are provided through hospital haematology services.

Private haematology consultations and blood tests are also available and can be a way of getting an earlier opinion on an unexpected result. In either case, ask for copies of your blood counts so that changes can be tracked over time, and ask what the working explanation is for the raised count.