Red Blood Cell Count- Understand the Test

At a Glance

Why Get Tested?

To evaluate any change in the number of red blood cells in your blood

When To Get Tested?

As part of a full blood count (FBC), which may be requested for a variety of reasons.

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?

Keep well hydrated by drinking fluids one to two days prior to blood collection

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?

This test counts the number of red blood cells (RBC) in a litre of blood. Red blood cells, which are made in the bone marrow, carry oxygen from the lungs to the cells and transport carbon dioxide from the cells to the lungs. Women tend to have lower RBC counts than men, and levels tend to decrease with age. When the value decreases by more than 10% of the expected normal value, the patient is said to be anaemic.

How is the sample collected for testing?

The test is performed on a blood sample taken by a needle placed in a vein in the arm or by a finger-prick (for children and adults) or heel-prick (for newborns).

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.

Common Questions

How is it used?

A RBC count is used to evaluate any type of decrease in red blood cells (anaemia) or increase in red blood cells (polycythaemia).
When is it requested?

A RBC count is normally requested as a part of the full blood count (FBC), which may be requested for many different reasons.
What does the test result mean?

A high RBC count may indicate congenital heart disease, dehydration, obstructive lung disease, sleep apnoea or bone marrow over-production. A low RBC count may indicate anaemia, bleeding, kidney disease, bone marrow failure (for instance, from radiation or a tumour), malnutrition, or other causes. A low count may also indicate nutritional deficiencies of iron, folate and vitamin B12.
Is there anything else I should know?

Normal decreases in red blood cells are seen during pregnancy as a result of normal body fluid increases that dilute them.

Living at high altitudes causes an increase in RBC counts—this is your body’s response to the decreased oxygen available at these heights.
How are abnormal red blood cell counts treated?

First, your doctor must determine the cause of your abnormal RBC count so that they can prescribe appropriate treatment. Treatment may include a vitamin or mineral supplement, a change in your nutrition, removal of excess red blood cells or replacement with red blood cells from a blood donor. Alternatively it may only require changing your current medication or prescribing a drug to stimulate red cell production in your bone marrow.
Can I test my RBCs at home?

No. This test is performed by trained laboratory personnel in an accredited laboratory using specialist equipment.
Do diet and nutrition help keep RBCs at healthy levels?

Yes, to the extent that if you eat a well-balanced diet, you can prevent iron deficiency anaemia. RBC problems that are caused by disease conditions are not likely to be corrected by diet.
Are there symptoms I should recognise if my RBCs are dangerously low or high?

Tiredness may indicate a low RBC count. Fainting, pallor (loss of normal skin colour), and shortness of breath also can indicate low RBCs, as do dizziness and an altered mental state that may be the result of dehydration.

When the RBC is high it may cause headaches, visual disturbances and a flushed appearance to the skin.

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