What Does a Low White Blood Cell Count Mean

This article provides an in-depth understanding of low white blood cell count, exploring what is the most common reason for low WBC. Discover the role of white blood cells in immune function, the causes of low WBC, and how lifestyle factors like diet, exercise, and stress management can influence WBC levels.

Ashley Reaver
By Ashley Reaver
Lucia Gcingca
Edited by Lucia Gcingca

Updated December 13, 2023.

a woman sitting in a chair wearing a face mask

White blood cells (WBC) are the driving force behind a healthy immune system. Yet, a low count in these combatant cells doesn't always spell trouble. Understanding their levels is best done by comparing recent results with your historical blood test data.

Here's a comprehensive overview of white blood cells, the reasons they might be low, and how to support their production. Explore reasons behind fluctuations in their numbers and learn tips to keep your immune defense strong.

What are white blood cells?

White blood cells, or leukocytes, are the body’s primary defense against infection. They are largely produced in the bone marrow, although the spleen plays a role in the production of some types of white blood cells, too. [1]

a blood test tube with blood and blood cells

WBC production is stimulated in response to infection, upon which they circulate throughout the blood and lymph systems. Your total white blood cell count is the sum of five different types of white blood cells, all with different roles in battling foreign invaders in the body:

  • Neutrophils
  • Eosinophils
  • Basophils
  • Lymphocyte
  • Monocytes

Low white blood cell counts can lead to increased susceptibility to infections, prolonged illness duration, and greater severity. However, these levels vary daily and hourly, so one blood test shouldn't be used to draw definitive conclusions about your immune health.

» Discover what you should know about a high white blood cell count

What are neutrophils?

Neutrophils make up the largest share of your white blood cell count, contributing 60-70% of the total. Hence, a low white blood cell count is likely due to a low neutrophil count, also called neutropenia.

Neutrophils are the immune system’s first responders—within minutes of an injury, trauma, or inflammation of tissue in the body, neutrophils are drawn to the scene. They essentially control traffic to and from an infection site by recruiting additional white blood cells specialized to the type of invader.

Neutrophils function by engulfing the pathogen and breaking it down. And even though they are microscopic, you’ve probably seen neutrophils, as they are the basis of pus! The lifespan of a neutrophil is very short, ranging from 5 hours to a few days.

What is a normal range for WBC count?

The definition of “normal” depends on the lab that processed your blood results. However, a normal white blood cell count is 4,000-11,000 per microliter of blood. This is usually reported as 4.0-11.0 thousand/μL.

If neutrophil counts are also measured, this corresponds to a count of 1500-7800 cells/ μL. You may also see this value represented as a percent of your total white blood cell count.

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Considerations for low white blood cell count

Before pinpointing the cause behind a low WBC measure, remember that a single data point can't give you a comprehensive answer. Ideally, you should be able to compare recent blood results with past ones to identify a pattern or a deviation from your “normal.”

WBC count is frequently tested as part of a complete blood count (CBC) panel, a routine test you might've had at your doctor's office or if you’ve ever been hospitalized. So track down past blood work and use it as a comparison point for your new results.

If your "normal" is lower than the defined normal range

The normal zones outlined above are based on the population as a whole. While well-defined, they don't necessarily cover 100% of the possible values for healthy, normal white blood cells. There is a percentage of the population that has a lower “resting state” level of WBC.

This is likely due to genetic variations and doesn't necessarily predispose you to an increased risk of infection. People of African, Middle Eastern, and particular regions of European descent may have been genetically predisposed to lower “resting” levels. [2, 3]

If you have a history of WBC levels just below the 4.0 thousand/μL normal cutoff and haven’t experienced a high incidence of illness throughout your life, you likely just have a lower “resting state.” Discuss your findings with your physician to rule out the need for any additional testing.

» Want to understand blood test results? Check out our guide on complete blood counts

Your WBC levels were once normal, but have been consistently low as of late

If you do not have a history of low WBC but have experienced a pattern of low results over recent months, you may be experiencing an issue with the production of white blood cells. [4] Having historical WBC data is key to identifying whether a low count is a new pattern.

Consistent counts below 3.5 thousand/μL, especially under 3.0 thousand/μL, should be discussed with your healthcare provider to determine the cause and consider further testing.

You usually have normal white blood cells but your last test result was low

A short-term low white blood cell count is usually due to acute neutropenia, a short period of time in which the absolute number of neutrophils in the blood is low. [4] Acute neutropenia, often occurring when your body's fighting an infection, results from high neutrophil usage or low production.

Neutrophils, having a short lifespan, die after engulfing a few pathogens, leading to their reduced levels in the blood and consequently lowering overall WBC count. However, a one-time low WBC measurement shouldn't cause concern.

If you feel well by the time you receive your blood test results—which can take several days—your WBC and neutrophil levels have likely normalized. A single low WBC count often indicates that your immune system is working as it should be.

Most common reasons for low white blood cell count

What causes low white blood cell count can range from relatively benign to more serious. The most common being:

  • Vitamin and mineral deficiencies: Vitamins and minerals such as vitamin B12, folate, B6, copper, and zinc are vital for WBC production. Deficiencies, often due to chronic malnutrition or alcoholism, can lead to low WBC counts. A blood test can determine if these nutrient levels are low, as supplementing them when not deficient is not advised.
  • Viral infections: Chronic viral infections like hepatitis B & C, HIV, and tuberculosis can lead to persistently low white blood cell levels. However, identifying these infections usually requires more than a single blood test, so one should not conclude the cause of low WBC from a single measurement.
  • Autoimmune diseases: Low white blood cell counts can results from some autoimmune conditions (like rheumatoid arthritis), as autoimmune diseases attack the immune system.
  • Bone marrow cancers: Cancers that impact the bone marrow can cause low WBC counts, as most most white blood cells are produced in the bone marrow. WBC counts would be extremely low in these situations, not just mildly below the normal range.
  • Treatment and medication: Some people develop low white blood cell counts due to medical treatments or medications, most prominently chemotherapy.

People with chronically low white blood cell counts need to be extra careful to avoid infections. Key preventive measures include frequent hand washing, wearing a face mask, and avoiding cuts or wounds. If wounds occur, they should be kept clean. Additionally, careful attention should be given to the source and preparation of food, especially in cases of severe low WBC.


Can exercise reduce white blood cell count?

Yes, high frequency of intense exercise, particularly in endurance sports, can reduce your white blood cell count and make you more susceptible to illness. This is often exhibited as upper respiratory infection in runners and cyclists during cold months.[5,6] Adequate rest days between high intensity workouts may help to reduce the incidence of upper respiratory infections.

Can low white blood cells cause fatigue?

Low white bloods cells likely aren’t the cause of fatigue. If you have low WBC and are increasingly feeling fatigued, both are likely symptoms of an underlying issue. This could be a range of issues, from over-exercise or overtraining, low folate or B12 levels, autoimmune diseases, viral infections, and certainly cancers.

6 ways to improve your white blood cell count

If your resting white blood cell count is low, lifestyle changes might not affect it. However, for other factors affecting WBC levels, certain actions can help lower the strain on your immune system and enhance protection against pathogens:

1. Manage your stress

Mental, emotional, and physical stress impact the body's ability to defend against infection. Allostatic load, the stress-induced wear on body and brain, influenced by adrenalin and cortisol, can compromise immune response as the body adapts to stressors. [7]

2. Get adequate sleep

The impact of inadequate sleep on white blood cells is well documented. Sleeping 6-8 hours per night can help you maintain normal levels of white blood cells, especially neutrophils. [8]

3. Engage in regular physical activity

Exercise affects white blood cell count and immune function in a U-shaped curve: both insufficient and excessive exercise raise infection risk. Regular moderate-intensity exercise, like 30 minutes daily for 5 days a week, supports optimal white blood cell levels. [9, 10]

For those doing intense training without rest days, decreasing high-intensity exercise frequency can help restore normal WBC levels.

4. Eat a variety of fruits and vegetables

Fruits and vegetables, rich in vitamins, minerals, antioxidants, and phytochemicals, support white blood cells and overall immune function. Key antioxidants to focus on include vitamins A, C, E, and selenium.

  • Vitamin A is in colorful fruits, vegetables, and dark leafy greens, and absorbs better with fat and varied preparation.
  • Vitamin C is in citrus, berries, broccoli, bell peppers, kiwis, and Brussels sprouts, with limited cooking to retain its content.
  • Vitamin E is mainly in nuts and seeds, with wheat germ, wheat germ oil, and sunflower seeds being prime sources. Selenium's top source is Brazil nuts, with two nuts daily fulfilling the recommended amount. [11, 12]
the four different types of food are shown

5. Maintain a healthy body weight

Excess body weight is associated with elevated levels of white blood cells, as it can cause an increase in inflammation and result in a WBC imbalance. [13]

6. Stop smoking

Smoking causes your white blood cell count to be elevated, as it causes your body to be in a constant state of inflammation and damage caused by tobacco. [14]

» Eager to safeguard your health? Explore how inflammation affects heart health

The best way to understand your white blood cell count

A history of blood data is the best way to understand a low white blood cell count. A single low WBC measure is not enough information for diagnosis. Speak with your physician about the need for follow-up testing.

To maintain a properly functioning immune system, take action on improving lifestyle factors related to your white blood cell count.

Learn what actions you can take to impact your white blood cell count by uploading your results and develop your Action Plan with InsideTracker.


[1] https://www.merckmanuals.com/home/blood-disorders/biology-of-blood/formation-of-blood-cells

[2] Crosslin DR, McDavid A, Weston N, et al. Genetic variants associated with the white blood cell count in 13,923 subjects in the eMERGE Network. Hum Genet. 2012;131(4):639‐652. doi:10.1007/s00439-011-1103-9

[3] Reich D, Nalls MA, Kao WH, et al. Reduced neutrophil count in people of African descent is due to a regulatory variant in the Duffy antigen receptor for chemokines gene. PLoS Genet. 2009;5(1):e1000360. doi:10.1371/journal.pgen.1000360

[4] Boxer, Laurence A. “ How to approach neutropenia.” Hematology. American Society of Hematology. Education Program vol. 2012 (2012): 174-82. doi:10.1182/asheducation-2012.1.174

[5] R. Horn, P L et al. “ Lower white blood cell counts in elite athletes training for highly aerobic sports.” European journal of applied physiology vol. 110,5 (2010): 925-32. doi:10.1007/s00421-010-1573-9

[6] S. König D, Grathwohl D, Weinstock C, Northoff H, Berg A. Upper respiratory tract infection in athletes: influence of lifestyle, type of sport, training effort, and immunostimulant intake. Exercise Immunology Review. 2000 ;6:102-120.

[7] McEwen, Bruce S. “ Stressed or stressed out: what is the difference?.” Journal of psychiatry & neuroscience : JPN vol. 30,5 (2005): 315-8.

[8] Faraut B, Boudjeltia KZ, Vanhamme L, Kerkhofs M. Immune, inflammatory and cardiovascular consequences of sleep restriction and recovery. Sleep Med Rev. 2012;16(2):137‐149. doi:10.1016/j.smrv.2011.05.00

[9] Johannsen, Neil M et al. “ Effect of different doses of aerobic exercise on total white blood cell (WBC) and WBC subfraction number in postmenopausal women: results from DREW.” PloS one vol. 7,2 (2012): e31319. doi:10.1371/journal.pone.0031319

[10] Willis EA, Shearer JJ, Matthews CE, Hofmann JN. Association of physical activity and sedentary time with blood cell counts: National Health and Nutrition Survey 2003-2006. PLoS One. 2018;13(9):e0204277. Published 2018 Sep 25. doi:10.1371/journal.pone.0204277

[11] Gravina, Leyre et al. “ Influence of nutrient intake on antioxidant capacity, muscle damage and white blood cell count in female soccer players.” Journal of the International Society of Sports Nutrition vol. 9,1 32. 19 Jul. 2012, doi:10.1186/1550-2783-9-32

[12] Colacino, Justin A., et al. " Dietary antioxidant and anti-inflammatory intake modifies the effect of cadmium exposure on markers of systemic inflammation and oxidative stress." Environmental research 131 (2014): 6-12.

[13] Vuong J, Qiu Y, La M, Clarke G, Swinkels DW, Cembrowski G. Reference intervals of complete blood count constituents are highly correlated to waist circumference: should obese patients have their own "normal values?". Am J Hematol. 2014;89(7):671‐677. doi:10.1002/ajh.23713

[14] Higuchi T, Omata F, Tsuchihashi K, Higashioka K, Koyamada R, Okada S. Current cigarette smoking is a reversible cause of elevated white blood cell count: Cross-sectional and longitudinal studies. Prev Med Rep. 2016;4:417‐422. Published 2016 Aug 9. doi:10.1016/j.pmedr.2016.08.009