What is the most common cause of leukopenia?

September 28, 2025 •

4 min read

Leukopenia, an abnormally low white blood cell count, is often a temporary condition caused by an infection or medication. We explore what is the most common cause of leukopenia and its various triggers, from infections to medications, autoimmune disorders, and more.

Quick Summary

The causes of leukopenia vary widely, with viral infections, chemotherapy, and autoimmune disorders among the most frequent triggers. Pinpointing the exact cause requires a comprehensive medical evaluation to determine if it stems from decreased production or increased destruction of white blood cells.

Key Points

Infections are a frequent cause: Many viruses, including influenza and HIV, as well as severe bacterial infections like sepsis, can cause leukopenia.
Medications, especially chemotherapy, are major culprits: Cancer treatments and various other drugs like immunosuppressants can suppress bone marrow function, leading to a low white blood cell count.
Autoimmune diseases can trigger leukopenia: Conditions like lupus (SLE) and rheumatoid arthritis can cause the immune system to mistakenly attack and destroy its own white blood cells.
Bone marrow disorders are a key factor: Issues like aplastic anemia, myelodysplastic syndromes, or cancer in the bone marrow can impair the production of white blood cells.
Nutritional deficiencies matter: Insufficient intake of vitamins like B12 and folate can impede the bone marrow's ability to produce healthy blood cells.
Diagnosis is crucial: Because the cause varies widely, professional medical evaluation through a complete blood count (CBC) is necessary to determine the root issue and appropriate treatment.

Understanding Leukopenia

Leukopenia is a medical condition defined by a decrease in the number of white blood cells (leukocytes) in the bloodstream. Since leukocytes are the body's primary defense against infection, a low count can weaken the immune system and increase susceptibility to illness. The specific cause of leukopenia is not always apparent and can range from acute, self-resolving issues to serious underlying medical conditions. The overall most common cause is often dependent on the patient's context, such as age, medication use, or pre-existing conditions.

Infectious Causes: The Immune Response

Many types of infections can lead to leukopenia, both by temporarily suppressing bone marrow function and by causing a rapid depletion of circulating white blood cells as the body fights the pathogen.

Viral Infections

Viral infections are a very common cause of transient leukopenia. During the initial phase of an infection, the body may use up its white blood cells, particularly neutrophils, faster than it can produce them. Specific examples include influenza, HIV/AIDS, mononucleosis, and viral hepatitis.

Severe Bacterial Infections (Sepsis)

In cases of overwhelming bacterial infection like sepsis, the body's intense immune response can rapidly deplete the white blood cell supply. A sudden drop in the white blood cell count during sepsis is a dangerous sign.

Medication Side Effects: A Significant Factor

Certain medications are a frequent cause of leukopenia, particularly those used in chemotherapy and radiation therapy for cancer, which target rapidly dividing cells including those in the bone marrow that produce white blood cells. Other medications that can induce leukopenia include immunosuppressants (like mycophenolate mofetil and azathioprine), antipsychotics (like clozapine), and certain antibiotics (like penicillin and sulfonamides).

Autoimmune Disorders: Targeting the Body's Own Cells

In autoimmune diseases, the immune system mistakenly attacks the body's own cells, which can include white blood cells. Conditions like Systemic Lupus Erythematosus (SLE) and Rheumatoid Arthritis can cause leukopenia by attacking white blood cells directly or suppressing their production in the bone marrow.

Comparison of Common Leukopenia Triggers


Feature	Infectious Causes	Autoimmune Disorders
Onset	Usually rapid (acute)	Often gradual (chronic)
Duration	Temporary, resolving with the infection	Can be chronic or persistent
Mechanism	Rapid utilization by immune system or temporary bone marrow suppression	Immune system attacks and destroys WBCs
Symptoms	Often includes fever, chills, illness related to the infection	Vary widely, including fatigue, joint pain, skin rashes

Bone Marrow Diseases and Disorders

Conditions that damage or impair bone marrow, the site of blood cell production, can lead to leukopenia. These include aplastic anemia, myelodysplastic syndromes (MDS), cancers like leukemia that crowd out healthy cells, and hypersplenism, where the spleen destroys white blood cells too quickly.

Nutritional Deficiencies

Deficiencies in key nutrients, such as Vitamin B12, folate, copper, and zinc, can impair the bone marrow's ability to produce white blood cells.

Conclusion: Seeking Professional Diagnosis

There is no single answer to what is the most common cause of leukopenia that fits every case, as the cause is highly dependent on an individual's health status. The most frequent causes include temporary viral infections, medication side effects (especially chemotherapy), and autoimmune disorders. Other significant factors include bone marrow diseases and nutritional deficiencies. It is crucial to consult a healthcare professional for a proper diagnosis and treatment plan. A detailed medical history, physical exam, and blood tests are necessary to uncover the root cause and ensure appropriate care.

This content is for informational purposes only and does not constitute medical advice. Please consult with a qualified healthcare provider for any health concerns. Autoimmune Diseases - NIH

How Is Leukopenia Detected?

Leukopenia is typically detected through a standard blood test called a Complete Blood Count (CBC). The specific type of white blood cell that is low can provide clues as to the underlying cause.

Can I Prevent Leukopenia?

Preventing leukopenia depends on its cause. For example, if it's a side effect of chemotherapy, doctors may prescribe growth factors. If it's related to diet, addressing nutrient deficiencies can help. Maintaining a healthy lifestyle is a good general strategy.

Is Leukopenia a Form of Cancer?

No, but it can be caused by certain cancers (like leukemia) or cancer treatments (like chemotherapy).

Can Diet Help with Leukopenia?

Yes, diet can be supportive, especially for deficiency-related leukopenia, with foods rich in Vitamin B12, folate, zinc, and copper. However, it's not a standalone treatment for severe cases.

How Can I Avoid Infections with Leukopenia?

Good hygiene, avoiding crowds and sick people, and being cautious with food safety are important. Your doctor may recommend additional precautions.

Is Leukopenia Always Serious?

Mild cases can be temporary and resolve on their own, especially if caused by a minor viral infection. However, persistent or severe leukopenia increases infection risk and requires medical evaluation.

How Quickly Does Leukopenia Resolve?

This depends on the cause. It can be a week or two for a mild viral infection or follow a predictable cycle with chemotherapy. Chronic conditions may lead to persistent leukopenia.

Frequently Asked Questions

Leukopenia itself often has no specific symptoms. Symptoms, such as fever, chills, and fatigue, typically arise from the underlying infection or disease that the weakened immune system is unable to fight.

Leukopenia is a low count of all white blood cells, while neutropenia is a low count of neutrophils specifically. Since neutrophils make up a large portion of the WBC count, neutropenia is the most common type of leukopenia.

Severe or chronic emotional and physical stress can potentially impact the immune system and lead to a drop in white blood cell counts. However, it is a less common cause than infections or medication.

Yes, some cases are identified as chronic idiopathic neutropenia, meaning a low neutrophil count occurs without any clear underlying cause. A specific gene variant also causes benign ethnic neutropenia in some populations.

Treatment depends entirely on the cause. It may involve treating an infection with antibiotics, adjusting medications, providing growth factors to stimulate WBC production, or addressing an underlying autoimmune or bone marrow disorder.

To minimize infection risk, individuals with leukopenia are often advised to avoid raw foods like uncooked meat, fish, and unwashed vegetables, as these can harbor harmful bacteria.

Doctors start with a thorough medical history and physical exam. This is followed by a CBC blood test. Depending on the findings, further tests might include a peripheral blood smear or a bone marrow biopsy.