What causes your neutrophils to decrease?

September 26, 2025 •

4 min read

Neutrophils, the most common type of white blood cell, are crucial for fighting off infections. When these vital cells drop to abnormally low levels, a condition known as neutropenia, it can compromise the body's immune defenses. Understanding what causes your neutrophils to decrease is the first step toward managing this condition and its associated health risks.

Quick Summary

Low neutrophil levels, or neutropenia, can be caused by various factors, including infections like HIV or hepatitis, cancer and its treatments (especially chemotherapy), autoimmune diseases such as lupus or rheumatoid arthritis, and certain medications like antibiotics and antipsychotics. Bone marrow disorders and nutritional deficiencies, such as a lack of vitamin B12 or folate, can also impair neutrophil production.

Key Points

Infections Trigger Depletion: Severe or chronic infections, especially viral ones like HIV and hepatitis, can cause a drop in neutrophils as the body rapidly uses them to fight the pathogen.
Chemotherapy is a Major Cause: Cancer treatments like chemotherapy and radiation can suppress the bone marrow's ability to produce neutrophils, often leading to a temporary state of neutropenia.
Autoimmune Diseases Destroy Cells: Conditions such as lupus and rheumatoid arthritis can cause the immune system to mistakenly attack and destroy healthy neutrophils, resulting in lower counts.
Bone Marrow Disorders Impair Production: Aplastic anemia, myelodysplastic syndromes, and certain genetic conditions directly impact the bone marrow's ability to create neutrophils.
Medications Can Cause Neutropenia: Numerous drugs, including certain antibiotics, antipsychotics (like clozapine), and antithyroid medications, can lead to decreased neutrophil levels.
Nutritional Deficiencies Play a Role: A lack of essential nutrients like vitamin B12, folate, or copper can disrupt the production of neutrophils in the bone marrow.
Severity Determines Risk: The risk of severe infection increases significantly with lower neutrophil counts, with severe neutropenia (ANC < 500 cells/μL) posing the highest risk.
Symptoms Indicate Infection: Neutropenia itself may not cause symptoms, but its complications, like frequent or severe infections, often present with fever, mouth sores, or fatigue.

Understanding Neutropenia: The Basics

Neutrophils are a type of white blood cell produced in the bone marrow that play a critical role in the immune system by destroying harmful bacteria and other pathogens. When the absolute neutrophil count (ANC) falls below 1,500 cells per microliter, a person is considered to have neutropenia. This condition can range from mild (1,000-1,500 cells/μL) to severe (below 500 cells/μL), with the risk of serious infection increasing as the count drops. Several factors can disrupt the normal production, distribution, or lifespan of neutrophils, leading to a decreased count.

Infections as a Cause of Decreased Neutrophils

One of the most common reasons for a temporary drop in neutrophils is an ongoing infection. The body consumes neutrophils faster than it can produce them to combat the invading pathogen. Some infections are particularly well-known for causing neutropenia:

Viral Infections: Viruses like HIV, hepatitis A, B, and C, Epstein-Barr virus (the cause of mononucleosis), measles, and influenza can suppress bone marrow function, leading to a decrease in neutrophil production.
Bacterial Infections: In cases of severe bacterial infections, such as sepsis, the overwhelming demand for neutrophils can lead to their rapid depletion. Some specific bacterial infections like tuberculosis or typhoid fever can also trigger neutropenia.

Medical Treatments and Drugs

Numerous medical treatments and medications can have the adverse effect of lowering neutrophil counts. Patients undergoing these treatments are often closely monitored for signs of neutropenia to prevent complications.

Cancer Treatments: Chemotherapy is a well-known cause of neutropenia because it targets and kills rapidly dividing cells, including those in the bone marrow that produce neutrophils. Radiation therapy can also affect bone marrow function if delivered to areas of the body where blood cells are produced.
Medications: A wide range of drugs can induce neutropenia, sometimes through direct bone marrow suppression or by triggering an immune response that attacks neutrophils. Examples include certain antibiotics, antithyroid medications, antipsychotics like clozapine, and some diuretics.
Bone Marrow Transplant: Patients undergoing a bone marrow or stem cell transplant may experience neutropenia as a temporary effect while the new stem cells establish themselves and begin producing blood cells.

Autoimmune Disorders and Chronic Conditions

In some cases, the body's own immune system mistakenly attacks and destroys healthy neutrophils. This is a common mechanism in autoimmune diseases.

Systemic Lupus Erythematosus (Lupus): This autoimmune disease can cause the body to produce antibodies that target and destroy neutrophils.
Rheumatoid Arthritis: A chronic inflammatory disorder, rheumatoid arthritis can sometimes lead to Felty's syndrome, a condition characterized by enlarged spleen, rheumatoid arthritis, and neutropenia.
Chronic Autoimmune Neutropenia: This condition is more common in children and is caused by anti-neutrophil antibodies that lead to the premature destruction of neutrophils. It is often benign and resolves over time.

Bone Marrow Disorders and Genetic Causes

Problems with the bone marrow itself, where neutrophils are manufactured, can significantly disrupt their production.

Aplastic Anemia: This rare but serious condition causes the bone marrow to stop producing enough new blood cells, including neutrophils.
Myelodysplastic Syndromes (MDS): A group of disorders caused by poorly formed or dysfunctional blood cells in the bone marrow. This can lead to low neutrophil counts, among other issues.
Inherited Conditions: Some genetic disorders are linked to neutropenia, such as Kostmann syndrome and Shwachman-Diamond syndrome.

Nutritional Deficiencies

An inadequate intake of certain vitamins and minerals is essential for blood cell production and can result in neutropenia.

Vitamin B12 and Folate Deficiency: Both are crucial for DNA synthesis and cell proliferation in the bone marrow. Deficiencies can impair the production of all blood cells, including neutrophils.
Copper Deficiency: A lack of copper can also lead to impaired neutrophil production.

Other Potential Causes

Beyond the primary categories, other factors can contribute to a drop in neutrophil levels.

Hypersplenism: An enlarged and overactive spleen can trap and destroy neutrophils, leading to a reduced count in the bloodstream.
Idiopathic Neutropenia: In some cases, extensive investigation fails to reveal a definitive cause for the low neutrophil count, and the condition is classified as chronic idiopathic neutropenia.

Comparison of Common Neutropenia Causes


Cause	Mechanism of Action	Common Examples	Treatment Approach
Infections	Rapid consumption of neutrophils; viral suppression of bone marrow	HIV, Hepatitis, Sepsis	Address underlying infection (e.g., antibiotics, antivirals)
Chemotherapy	Direct suppression and destruction of rapidly dividing bone marrow cells	Doxorubicin, Cyclophosphamide	Granulocyte colony-stimulating factor (G-CSF); dose adjustments
Autoimmune Disease	Immune system produces antibodies that attack neutrophils	Lupus, Rheumatoid Arthritis, Felty's Syndrome	Immunosuppressants (e.g., corticosteroids), G-CSF
Bone Marrow Disorders	Defective production of blood cells in the bone marrow	Aplastic Anemia, Myelodysplastic Syndromes	Stem cell transplant, G-CSF, immunosuppression
Medications	Drug toxicity or immune-mediated destruction of neutrophils	Antibiotics, Antipsychotics (Clozapine)	Discontinue causative drug; G-CSF if needed
Nutritional Deficiency	Lack of essential vitamins and minerals needed for blood cell formation	Vitamin B12, Folate, Copper deficiency	Supplementation of deficient nutrients

Conclusion

Decreased neutrophils can result from a wide array of underlying issues, ranging from temporary viral infections to chronic autoimmune conditions and the side effects of medications. Accurate diagnosis is critical and typically begins with a complete blood count (CBC) to measure the neutrophil level, followed by further investigation based on a patient's medical history and clinical presentation. Management focuses on treating the underlying cause, whether through discontinuing a medication, managing an infection, or addressing a bone marrow disorder. Patients with significantly low neutrophil counts must take precautions to minimize their risk of serious infection. For detailed, authoritative medical information, a reliable resource is the National Center for Biotechnology Information's StatPearls on Neutropenia.

Frequently Asked Questions

Neutropenia is a medical condition defined by a lower-than-normal count of neutrophils, a type of white blood cell that plays a primary role in fighting infection. The severity of neutropenia varies, with a higher risk of infection occurring at lower neutrophil levels.

Yes, many causes of a low neutrophil count are temporary. For example, neutropenia caused by a viral infection typically resolves once the body has fought off the infection. Similarly, neutropenia due to chemotherapy is often transient, with neutrophil levels recovering over time.

Several infections are commonly associated with neutropenia. These include viral infections such as HIV, hepatitis, Epstein-Barr virus, and influenza, as well as bacterial infections like tuberculosis, typhoid fever, and severe sepsis.

In autoimmune diseases like lupus or rheumatoid arthritis, the body's immune system mistakenly attacks its own healthy cells. It can produce antibodies that target and destroy neutrophils, leading to a decreased count.

The initial step is a complete blood count (CBC) to confirm the low neutrophil level. Further diagnosis may involve reviewing a patient's medical history, evaluating medications, blood smears, and, in some cases, a bone marrow biopsy or genetic testing to determine the underlying cause.

Untreated neutropenia, particularly if severe, can leave the body vulnerable to serious infections. Since neutrophils are the first line of defense, even normally harmless bacteria can cause life-threatening infections in people with very low counts.

Neutropenia itself often has no specific symptoms. Instead, the symptoms that appear are from the infections that develop as a result. These can include fever, frequent illnesses, mouth sores, skin abscesses, and fatigue.

Yes, a diet lacking in certain key nutrients can impair neutrophil production. Deficiencies in vitamin B12, folate, and copper have all been linked to neutropenia.