What decreases your WBC? A comprehensive guide to leukopenia causes

November 30, 2025 •

3 min read

According to Mayo Clinic, a low white blood cell (WBC) count can result from a number of factors, including chemotherapy, infections like HIV, and autoimmune disorders. Knowing what decreases your WBC is critical because these cells are vital components of your immune system, defending your body against infections and disease.

Quick Summary

A low white blood cell count, known as leukopenia, can be caused by conditions like bone marrow disorders, infections, autoimmune diseases, cancer treatments, and nutritional deficiencies. The reduced cell count leaves the body more vulnerable to illness and complications. Diagnosis is typically made via a blood test.

Key Points

Diverse Causes: Leukopenia, or a low white blood cell count, can result from numerous factors including medications, infections, and underlying medical conditions.
Bone Marrow Impact: Disorders or cancers affecting the bone marrow, where WBCs are produced, are a major cause of decreased white blood cell counts.
Chemotherapy's Effect: Cancer treatments like chemotherapy and radiation often decrease WBCs because they destroy rapidly dividing cells in the bone marrow, including immune cells.
Autoimmune Self-Attack: Autoimmune conditions such as lupus or rheumatoid arthritis can cause the body's immune system to attack its own white blood cells.
Infection Overwhelm: Severe infections like sepsis or HIV can deplete the body's white blood cell supply faster than it can be replenished.
Nutritional Role: Deficiencies in essential nutrients like vitamin B12 and folate can impair WBC production.

What is a Low White Blood Cell Count?

A low white blood cell (WBC) count, or leukopenia, occurs when the number of leukocytes falls below the normal range. These cells are essential for the immune system, fighting off pathogens. A low count weakens the immune system, raising the risk of infection. While temporary drops can happen after viral illnesses, persistent leukopenia may indicate a more serious issue.

Medical Conditions that Cause Low WBC

Various diseases can affect WBC production or destroy existing cells.

Bone Marrow Disorders

The bone marrow produces blood cells, including WBCs. Conditions damaging bone marrow function can cause low counts. Examples include:

Aplastic Anemia
Myelodysplastic Syndromes (MDS)
Myelofibrosis
Cancers like leukemia, lymphoma, and multiple myeloma

Autoimmune Diseases

Autoimmune diseases involve the immune system attacking healthy cells, sometimes including WBCs. Examples are:

Systemic Lupus Erythematosus (Lupus)
Rheumatoid Arthritis
Crohn's Disease

Severe Infections

While some infections raise WBCs, severe or prolonged infections can deplete them.

HIV/AIDS attacks lymphocytes.
Sepsis uses up WBCs rapidly.
Viral Hepatitis can disrupt bone marrow.
Tuberculosis can cause a decrease.

Congenital Disorders

Some genetic conditions affect WBC production from birth. Kostmann syndrome is a rare example.

External Factors and Lifestyle Influences

External factors and lifestyle also contribute to low WBC counts.

Medications and Treatments

Certain medical treatments interfere with cell production.

Chemotherapy and radiation therapy destroy bone marrow cells.
Some antibiotics, like minocycline, can induce leukopenia.
Immunosuppressants can lower WBCs.
Other medications, including some antiepileptics and antipsychotics, may also be involved.

Nutritional Deficiencies

Lack of nutrients can hinder blood cell production.

Vitamin B12 and Folate are essential.
Copper and Zinc deficiencies can also impact production.

Lifestyle Factors

Poor lifestyle habits can negatively affect immune health.

Excessive alcohol consumption interferes with nutrient absorption.
Malnutrition weakens the immune system.
Chronic stress can suppress the immune system.

Comparison of Major Leukopenia Causes


Cause Category	Primary Mechanism	Examples	Recovery Time	Risk Level
Cancer Treatments	Direct destruction of bone marrow cells	Chemotherapy, Radiation	Often temporary, follows treatment cycle	High (due to severe neutropenia)
Autoimmune Diseases	Immune system attacks own WBCs	Lupus, Rheumatoid Arthritis	Varies; often chronic	Variable
Severe Infections	Rapid consumption of WBCs	HIV/AIDS, Sepsis, Viral Hepatitis	Varies based on infection severity	High (potential for serious complications)
Bone Marrow Disorders	Impaired or abnormal WBC production	Aplastic Anemia, Myelofibrosis	Can be long-term or permanent	High
Medications	Interference with cell production	Antibiotics, Immunosuppressants	Reversible upon discontinuation	Variable
Nutritional Deficiency	Lack of essential nutrients	B12, Folate, Zinc deficiency	Reversible with dietary changes/supplements	Variable

What to Do If You Have Low WBC

If a low WBC count is detected, a healthcare provider will identify the cause. Treatment addresses the root issue and may involve changing medications, treating infections, or using growth factors. Preventing infection is crucial while the immune system is compromised.

Infection Prevention Strategies

Key strategies include frequent handwashing, safe food handling, avoiding sick individuals, staying vaccinated, and monitoring for infection symptoms.

Conclusion

Understanding what decreases your WBC is vital for management. Causes range from temporary infections to chronic conditions and cancer treatments. Identifying the cause and following medical advice helps the immune system recover and minimizes complications. Always consult a healthcare professional for diagnosis and treatment. For more information, visit the American Society of Hematology.

Frequently Asked Questions

Chemotherapy and radiation therapy for cancer are among the most common causes of low white blood cell counts, as these treatments are designed to kill rapidly dividing cells, including healthy immune cells in the bone marrow.

Yes, infections can cause a low WBC count. Acute viral illnesses like the flu can temporarily reduce the number of white blood cells, and severe or overwhelming infections, such as sepsis or HIV, can rapidly consume WBCs, causing the count to drop.

Autoimmune diseases linked to low white blood cell counts include Systemic Lupus Erythematosus (Lupus) and Rheumatoid Arthritis, where the immune system attacks and destroys its own healthy cells, including WBCs.

Yes, many other medications can cause leukopenia, including some antibiotics, immunosuppressants used for organ transplants, antipsychotic drugs, and medications for an overactive thyroid.

Yes, malnutrition and deficiencies in certain vitamins and minerals, particularly vitamin B12, folate, copper, and zinc, can interfere with the body's ability to produce healthy white blood cells.

The underlying cause of a low WBC count is determined through various methods, including a Complete Blood Count (CBC) test, a review of recent infections or medications, and sometimes a bone marrow biopsy for more persistent cases.

A primary risk of a low WBC count is an increased susceptibility to infections, which can sometimes become severe or life-threatening. Symptoms of infection like fever, mouth sores, or persistent fatigue warrant immediate medical attention.