Also Known As
Packed cell volume
haematocrit
Formal Name
PCV
This article was last reviewed on
This article waslast modified on 30 June 2022.
At a Glance
Why Get Tested?

If your doctor suspects that you have anaemia (too few red blood cells), polycythaemia (too many red blood cells), or dehydration

When To Get Tested?

As part of a full blood count (FBC), a general blood screening test which may be requested for a variety of symptoms such as headaches, blurred vision, tiredness, itchy skin, difficulty in breathing and dizziness.

Sample Required?

A blood sample taken from a vein in your arm or by a finger-prick (children and adults) or heel-prick (newborns)

Test Preparation Needed?

No test preparation is needed

On average it takes 7 working days for the blood test results to come back from the hospital, depending on the exact tests requested. Some specialist test results may take longer, if samples have to be sent to a reference (specialist) laboratory. The X-ray & scan results may take longer. If you are registered to use the online services of your local practice, you may be able to access your results online. Your GP practice will be able to provide specific details.

If the doctor wants to see you about the result(s), you will be offered an appointment. If you are concerned about your test results, you will need to arrange an appointment with your doctor so that all relevant information including age, ethnicity, health history, signs and symptoms, laboratory and other procedures (radiology, endoscopy, etc.), can be considered.

Lab Tests Online-UK is an educational website designed to provide patients and carers with information on laboratory tests used in medical care. We are not a laboratory and are unable to comment on an individual's health and treatment.

Reference ranges are dependent on many factors, including patient age, sex, sample population, and test method, and numeric test results can have different meanings in different laboratories.

For these reasons, you will not find reference ranges for the majority of tests described on this web site. The lab report containing your test results should include the relevant reference range for your test(s). Please consult your doctor or the laboratory that performed the test(s) to obtain the reference range if you do not have the lab report.

For more information on reference ranges, please read Reference Ranges and What They Mean.

What is being tested?

Blood is a mixture of cells and plasma. The packed cell volume (PCV) is a measurement of the proportion of blood that is made up of cells. The value is expressed as a percentage or fraction of cells in blood. For example, a PCV of 40% means that there are 40 millilitres of cells in 100 millilitres of blood.

Red blood cells account for nearly all the cells in the blood. The PCV increases when the number of red blood cells increases or when the total blood volume is reduced, as in dehydration. The PCV falls to less than normal, indicating anaemia, when your body decreases its production of red blood cells or increases its destruction of red blood cells, or the blood cells are diluted by increases in total volume (haemodilution, for example occurring during pregnancy).

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Common Questions
  • How is it used?

    This test is used to diagnose or evaluate anaemia (decrease of red blood cells), polycythaemia (increase in red blood cells) or dehydration; which may be referred to as relative polycythaemia.

  • When is it requested?

    The PCV is normally requested as a part of the full blood count (FBC). It is also repeated at regular intervals for many conditions, including:  

    • Monitoring treatment of anaemia, polycythaemia or dehydration.
    • Monitoring the need for or effectiveness of blood transfusions, monitoring of ongoing bleeding to check its severity.
  • What does the test result mean?

    A decreased PCV indicates anaemia, or haemodilution. Haemodilution is usually obvious due to administration of a bolus of intravenous fluids (water containing solutions into the blood stream) or pregnancy. Further testing may be necessary to determine the exact cause of anaemia.

    Conditions that can result in a low PCV include

    • Bleeding
    • Nutritional - iron, vitamin (e.g. B12 or folate) or other mineral deficiencies
    • Inflammatory conditions such as rheumatoid arthritis
    • Kidney disease (healthy kidneys secrete a hormone erythropoietin or “epo” which stimulates red blood cell production in the bone marrow)
    • Cirrhosis of the liver
    • Haemolysis, where the red cells are being destroyed prematurely either due to attack by the body’s immune system, due to organ damage or due to inherited abnormalities of the red cells or the haemoglobin they contain
    • Bone marrow disorders such as aplastic anaemia, myelodysplastic syndrome, leukaemia, lymphoma or myeloma
    • Some medicines– including chemotherapy

    The most common cause of increased PCV is dehydration, and with adequate fluid intake, the PCV returns to normal. However, it may reflect a condition called polycythaemia where there are too many red cells.

    In primary polycythaemia (polycythaemia vera, PV, or, polycythaemia rubra vera, PRV) the bone marrow overproduces red blood cells of its own accord.

    More commonly polycythaemia is due to factors outside the bone marrow (secondary polycythaemia). Causes of secondary polycythaemia include:

    • Some lung or heart diseases where the bone marrow manufacturers more red blood cells in order to carry enough oxygen throughout your body
    • Excessive alcohol consumption
    • Smoking
    • Liver or kidney disease
    • Obesity
    • Drug induced - testosterone, growth hormone, EPO and diuretics
    • Some tumours which can secrete erythropoietin (“epo”), stimulating the production of red blood cells
    • Rare inherited haemoglobins, which don’t release enough oxygen to the body
  • Is there anything else I should know?

    Pregnancy usually causes a slightly decreased PCV due to extra fluid in the blood.

    Living at high altitudes causes an increased PCV - this is your body's response to the decreased pressure of oxygen available at these heights.

    Recent blood transfusion may give a misleading result.

    You may have an ultrasound scan of the kidneys if a high PCV result is detected and possibly a blood test called EPO and JAK2.

    In polycythaemia vera you may also have increased white cell cells and platelets.

  • How do you treat anaemia?

    Treatment will depend upon the type of anaemia and the cause. Folic acid, vitamin B12 replacement, iron, and packed red cell transfusion are some therapies used to treat anaemia.

  • How do you treat polycythaemia?

    Treatment aims to prevent symptoms and complications and treat underlying causes. This may be done by removing blood or taking medication to reduce PCV. You may be given medication to prevent blood clots. Improving lifestyle such as stopping smoking, drinking less alcohol and losing weight can decrease risk of potential blood clots.

  • Can I measure my PCV at home?

    No. This test is performed by trained laboratory personnel.

  • Is anyone more at risk for abnormal PCV values?

    People who have a chronic illness (such as rheumatoid arthritis), an inherited blood disorder, or malnutrition are at risk for an abnormal PCV. Women of childbearing age may have temporary decreases in PCV during menstrual periods and pregnancy.

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