Erythrocyte Count (RBC) Test

The erythrocyte (RBC) count test measures the number of red blood cells in a sample of blood. It is also known as RBC blood test and red blood cell (RBC) count test.

Red blood cells contain an important protein known as haemoglobin, which is responsible for carrying oxygen to different body tissues via blood. Abnormal red blood cell count may be seen in individuals with anaemia (low number of red blood cells) or other conditions such as myelofibrosis (fibrous scar tissue replaces the bone marrow) and paroxysmal nocturnal haemoglobinuria (a condition characterised by the breakdown of red blood cells faster than normal). Hence, the RBC blood test is used by doctors to diagnose and monitor anaemia and other associated conditions and guide appropriate treatment.

The erythrocyte count RBC blood test is recommended for individuals who are experiencing the symptoms of anaemia, which include:

• Headaches
• Difficulty focusing
• Loss of appetite
• Fatigue
• Brittle nails
• Mouth ulcers
• Difficulty breathing

The following categories of people are highly recommended to take the RBC blood test:

• Pregnant women – During pregnancy, haemoglobin and red blood cells may decrease. Hence, testing is important to ensure a healthy pregnancy.
• Individuals with vitamin B12 deficiency – Vitamin B12 is necessary to make red blood cells. RBC count test is important to check the risk of vitamin B12 deficiency anaemia.
• Individuals with iron deficiency anaemia – Iron helps the body make red blood cells. In such cases, the erythrocyte test is important to evaluate possible iron-deficiency anaemia.
• Individuals with folic acid deficiency – Folic acid is important for the growth and formation of red blood cells. Individuals with folic acid deficiency are at risk of anaemia and hence need to be tested.

The RBC blood test is used along with other blood tests to help diagnose and monitor conditions such as:

• Anaemia – This condition is characterised by the lack of healthy red blood cells. There are different types of anaemia based on the underlying cause:
• Anaemia due to vitamin B12 deficiency
• Anaemia due to folate deficiency
• Anaemia due to iron deficiency
• Anaemia of chronic disease
• Haemolytic anaemia (caused by breakdown of red blood cells)
• Idiopathic aplastic anaemia (bone marrow does not make enough blood cells due to unknown causes)
• Megaloblastic anaemia (the body produces unhealthy and abnormally large blood cells)
• Pernicious anaemia (low production of healthy red blood cells due to inadequate absorption of vitamin B12)
• Sickle cell anaemia (red blood cells become sickle-shaped due to an inherited disorder)
• Thalassaemia (an inherited disorder in which the body does not produce enough healthy haemoglobin)
• Myelofibrosis – This is a condition in which fibrous scar tissue replaces the bone marrow.
• Alport syndrome – This is an inherited disorder that affects the kidneys.
• Paroxysmal nocturnal haemoglobinuria (PNH) – This is a condition characterised by the breakdown of red blood cells faster than normal.
• Leukaemia – This refers to a type of cancer that affects the white blood cells.
• Multiple myeloma – This is a type of cancer that starts in plasma cells, a type of white blood cell in the bone marrow.

What to Expect Before the Erythrocyte Count (RBC) Test

No fasting is required for a standalone erythrocyte count (RBC) test. You can eat and drink normally. However, if it is part of a broader package that includes fasting tests, your doctor may advise fasting for 8-12 hours. Avoid strenuous exercise for 24 hours before the test, as intense physical activity can temporarily raise erythrocyte count (RBC) levels and affect interpretation. Always inform your doctor about any ongoing medications.

What to Expect During the Blood Collection

A phlebotomist cleans the skin with an antiseptic, then places an elastic band around your upper arm to make the veins easier to access. A small needle is inserted into the vein; you may feel a brief pinch. Blood is collected into a labelled tube in under a minute.

What to Expect After the Erythrocyte Count (RBC) Test

A small cotton swab and bandage are placed over the site to stop any minor bleeding. You can return to normal activities immediately. Minor bruising is normal and disappears quickly. If dizzy, sit and rest for a few minutes.

In the RBC blood test, the primary parameter being measured is:

• The number of red blood cells (erythrocytes) in a sample of blood.

The RBC blood test normal range is indicated in the table below.

The table below provides a general interpretation of the RBC blood test results based on whether the levels are low or high.

Like any other medical test, this test also has some risks and limitations.

Risks:

The RBC blood test is generally safe. You might have slight pain, bruising, or discomfort when the needle is inserted into your arm for collecting the blood sample that usually heals quickly without treatment.

Limitations:

• Certain medications can affect your test results. These include anabolic steroids, testosterone, quinidine, chemotherapy medicines, and methyldopa. Talk to your doctor if you need to temporarily stop taking any medicine.
• The test cannot differentiate between the different types of anaemias. Further testing is required to find out the underlying cause of your condition.1

Depending on your symptoms and results, your doctor may recommend certain additional tests to better understand your condition. These may include:

• Complete blood count
• Iron test
• Vitamin B12 test
• Folic acid test
• Reticulocyte count test
• Haemoglobin test
• Coombs test