White Blood Cell Count (WBC)

July 21, 2020

What are white blood cells?

White blood cells (WBC), also known as leucocytes, belong to the immune system and help to protect the body from infectious disease and invading pathogens. They are made in the bone marrow and can be found throughout the body. White blood cells can be classified into different groups, granulocytes, lymphocytes and monocytes.[1]

Why take a WBC blood test?

A white blood cell count determines how many white blood cells are present in a sample of blood. The count is a good marker for the presence of illness or infection. When an infection is present, the white blood count will rise, a process called leucocytosis which usually arises from inflammation, bacterial infections and leukaemia.

A reduced white blood cell count, however, is called leucopenia and is caused by various factors including medication, bone marrow disorders, vitamin deficiencies and liver disease.[2]

The different white blood cells are neutrophils, lymphocytes, monocytes, eosinophils and basophils.

You can check your level of white blood cells with Forth’s Vitality and Ultimate blood tests. For those who lead active lifestyles Forth also offers a home finger-prick blood test called Baseline Plus which includes analysis of white blood cells as well as 17 other biomarkers.

​What function do white blood cells have in the body?

The main function of white blood cells is to defend the body against infectious disease.[3] The make up a significant part of the immune system. White blood cells can be split into different categories. White blood cells are all different shapes and sizes, some have multiple-lobed nuclei, others have a large round nucleus and some have granules within their cytoplasm to fight infection. However, they all have different roles within the immune system.


Neutrophils are the most common white blood cells in circulation. They help to protect the body bacterial and fungi infection. Neutrophils are a type of phagocyte which means they can engulf and digest an invading pathogen.


There are two major forms of lymphocytes, B and T cells. These cells are the most important cells in the adaptive immune response where they are responsible for destroying invading pathogens.


Monocytes develop into one of two cell types, macrophages and dendritic cells. [4] Macrophages are phagocytes while dendritic cells flag foreign cells for destruction by lymphocytes, making them antigen-presenting cells.


Eosinophils are a type of granulocyte. Their roles include:

  • Presentation of antigens
  • Release of mediators for acute and chronic inflammation
  • Degranulation upon the presentation of helminth worms or parasites[5]


Basophils are also a type of granulocyte, releasing disease-fighting granules when they meet an infectious agent. The substances contained in granules include:

  • Histamine
  • Heparin
  • Peroxidase
  • Platelet-activating factor

How do changes in WBC affect health and wellbeing?

Leucocytosis is an elevated white blood cell count and can be caused by several factors. Increases in white blood cells can indicate infection or inflammation and so the side effects can negatively affect your health and wellbeing. A white blood cell count can indicate illness or infection within the body. It can also increase when the body is under emotional stress or because of intense and excessive exercise.

A decreased white blood cell count, leucopenia, can also be caused by diseases and disorders.

If you are worried about your immune levels or just want to check where you fall on the range, you can test your WBC level with Forth’s leading blood test service.

What can cause WBC to change?

Leucocytosis can be increased because of external stimuli such as:

  • Infection
  • Inflammation
  • Leukaemia
  • Trauma
  • Medication
  • Surgery

Leucopenia, on the other hand, can be a result of:

  • Medication like chemotherapy or radiotherapy
  • Bone marrow disorders
  • Vitamin deficiencies like vitamin B12 or folate
  • Liver disease
  • Enlarged spleen
  • Immune system diseases
  • Rheumatoid arthritis or systemic lupus erythematosus

What are the most common symptoms of high or low WBC?

The most common symptoms will depend on the type of infection which has entered the body. For example, some white blood cells, like basophils, can cause an allergic response where the body thinks identifies a substance as harmful. Therefore, causing symptoms most associated with allergies. For example. Basophils are often implicated in food allergies, the most common cause of anaphylaxis. Symptoms of anaphylaxis include:

  • Feeling faint or lightheaded
  • Difficulty breathing
  • Wheezing
  • Fast heartbeat
  • Anxiety
  • Confusion
  • Clammy skin
  • Collapse or losing consciousness

Other white blood cells may be implicated in the inflammatory response of the body. The most common symptoms of inflammation are:

  • Pain
  • Heat
  • Redness
  • Swelling
  • Loss of function

The symptoms caused by various infections can differ depending on the cause. However, always look out for fever as this can be a classic sign of infection, but other signs may be fatigue, vomiting, diarrhoea, coughing or muscular aches and pains.

How to keep WBC in the healthy range

There are many factors which can impact on immune dysfunction, such as:

  • stress
  • malnutrition
  • exposure to contaminants

Diet is a key factor in the function of the immune system. It is important to get the right calorie and protein intake because not getting enough, can reduce the T cell memory function in response to antigens. Vitamins are also vital, particularly vitamins A, C and E. Vitamin A has roles in the control of both the innate and adaptive immune responses as well as helping to mature T cells in the thymus. While vitamins C and E help lymphocytes to proliferate.[6]

Staying hydrated is also vital for the immune system status. Saliva contains the antibody, IgA, which acts as the body’s first line of defence against infection. For that reason, the body needs enough fluid to ensure enough saliva is produced. Equally, the liquid part of the blood consists of water and so, hydration is important to keep the blood volume at adequate levels, especially as many immune cells travel in the bloodstream to reach their target.

- Health scores calculated



[1] Blumenreich MS. (1990). The White Blood Cell and Differential Count. In: Walker HK, Hall WD, Hurst JW, editors. Clinical Methods: The History, Physical, and Laboratory Examinations. 3rd edition. Boston: Butterworths. Available from: https://www.ncbi.nlm.nih.gov/books/NBK261/

[2] Lab Tests Online UK. (2018). White Blood Cell Count. Available at: https://labtestsonline.org.uk/tests/white-blood-cell-count

[3] Science Daily. (2019). White Blood Cell. Available at: https://www.sciencedaily.com/terms/white_blood_cell.htm

[4] Karlmark, K, R., Tacke, F and Dunay, I, R. (2012). Monocytes in Health and Disease-Minireview. European Journal of Microbiology and Immunology: 2, pp 97-102.

[5] Kovalszki, A and Weller, P, F. (2016). Eosinophilia. Prim Care: 43(4), pp 43(4).

[6] Kafeshani, M. (2015). Diet and Immune System. Immunopathologia Persa: 1(1).

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This information has been medically reviewed by Dr Nicky Keay

Nicola has extensive clinical and research experience in the fields of endocrinology and sport and exercise medicine. Nicky is a member of the Royal College of Physicians, Honorary Fellow in the Department of Sport and Exercise Sciences at Durham University and former Research Fellow at St. Thomas' Hospital.

Dr Nicky Keay

Dr Nicky Keay

BA, MA (Cantab), MB, BChir, MRCP.