What Does a Low Neutrophil Count on a CBC Mean?
A low neutrophil count, called neutropenia, is a lower-than-expected number of the white blood cells that help defend against bacterial and fungal infections, often defined as an absolute neutrophil count (ANC) below about 1,500 cells per microliter of blood, though the exact cutoff varies with the
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Written By: DocAi Health Editorial Team
Last Updated: 2026-09-30
Last Updated: 2026-09-30
Medical Disclaimer: This article is for general informational and educational purposes only and is not medical advice. It does not create a doctor-patient relationship and is not a substitute for professional diagnosis or treatment by a qualified healthcare provider. Never disregard or delay seeking professional medical advice because of something you have read here. If you think you may have a medical emergency, call 911 or your local emergency number right away. Health information can change and this guidance is general and US-focused, so consult a licensed clinician in your own country about your specific situation.
A low neutrophil count, called neutropenia, is a lower-than-expected number of the white blood cells that help defend against bacterial and fungal infections, often defined as an absolute neutrophil count (ANC) below about 1,500 cells per microliter of blood, though the exact cutoff varies with the lab and age. A mild, isolated low ANC can occur temporarily after a viral infection, but the cause depends on the degree of neutropenia, previous counts, medications, and other findings. Other causes include medication side effects, autoimmune conditions, nutritional problems, inherited patterns, and, less commonly, problems inside the bone marrow. This article covers what your number can mean, common causes, and when a low count needs care quickly.
What Neutrophils Do and Why This Number Matters
In adults, neutrophils are usually the largest group of white blood cells in the bloodstream, and they are a major part of your body's defense against bacterial and fungal infections. They are made in your bone marrow, live only a short time once they enter circulation, and have to be replaced constantly. When something interrupts that supply line, whether it is a virus, a medication, or a bone marrow problem, the neutrophil count can drop, and it may be the first count affected or one of several.
A complete blood count (CBC) with differential reports your white blood cells by type. Neutrophils usually make up the largest share of that total, though the absolute neutrophil count (ANC) itself, the actual number of neutrophils per microliter of blood, matters more than the percentage. Your lab report may list this as "ANC," "absolute neutrophils," or "segs" plus "bands," and it will flag a result below the reference range as low. Our complete blood count guide covers the whole CBC panel; this article focuses on the neutrophil count alone.
A low total white blood cell count is not the same as a low neutrophil count. MedlinePlus explains that a standard CBC counts all white blood cells together, while a CBC with differential counts each type separately, so the total can look normal when the neutrophil count is low, and the reverse can also happen.
What Counts as a Low Neutrophil Count
Many US labs and hematology guidelines consider an ANC below about 1,500 cells per microliter to be neutropenia in adults. The European Hematology Association guidelines give 1,500 cells per microliter (1.5 billion per liter) as the general cutoff from age 1 year through adulthood, note that some adult references use 1,800, and point out that the definition varies with age and with inherited factors such as the Duffy-null variant described below. Some cancer-care resources use a lower number: MedlinePlus describes neutropenia in adults with cancer as fewer than 1,000 neutrophils per microliter. A result just under 1,500 is a reason to look at the context, not a diagnosis by itself: your lab's range, your age, your earlier results, and your Duffy status can all change how a number is read. A low count is roughly the mirror image of a high white blood cell count, which usually points toward infection or inflammation rather than a weakened defense. Doctors sort a low count into tiers, since infection risk can change at each level.
Mild, Moderate, and Severe Neutropenia
The same European guidelines classify neutropenia as mild, moderate, or severe, as the table below shows. Mild isolated neutropenia does not necessarily mean a major increase in infection risk, particularly when it is longstanding and otherwise unexplained, but risk depends on the cause, the duration, other immune problems, and whether other blood cell lines are affected. The guidelines add that infection risk depends on a person's capacity to recruit and deliver neutrophils to the tissues, not only on the ANC. In severe neutropenia the body can struggle to mount a normal defense against bacteria, and MedlinePlus notes that when the neutrophil count gets low enough, even bacteria that normally live in the mouth, skin, and gut can cause serious infections. The Infectious Diseases Society of America guideline for people with cancer notes that the term profound is sometimes used for an ANC below 100; this is an oncology term, not a cutoff for everyone with a low count.
| ANC (cells per microliter) | Usual label | General interpretation |
|---|---|---|
| 1,000 to 1,500 | Mild | Often limited risk, depending on the cause and context |
| 500 to 1,000 | Moderate | Infection risk may be higher |
| Below 500 | Severe | Higher risk of serious infection, which can progress quickly |
| Below 100 | Profound (a cancer care term) | Particularly high risk in that setting |
These categories are commonly used in practice, but infection risk also depends on the cause, duration, other immune problems, and clinical context.
Not everyone with a lower baseline count has a medical problem. Some healthy people have a naturally lower ANC associated with the Duffy-null (ACKR1) phenotype, called Duffy-null associated neutrophil count (DANC) and historically labeled benign ethnic neutropenia. The American Society of Hematology notes that people with the Duffy-null phenotype have no increased risk of infection because of it, and that it is most commonly found among people with African or Arabian Peninsula genetic ancestry, though it is not exclusive to them. Genetic ancestry alone cannot establish DANC, and ASH cautions that using race or ethnicity as a proxy for a genetic trait requires extreme caution, so a low count should not be assumed to be harmless on that basis. Duffy-status testing may help clarify whether a chronically low ANC is related to DANC when the clinical context makes this relevant; the European guidelines describe testing for the ACKR1/DARC variant as reasonable in chronic, mild neutropenia. A history of the same reading on past CBCs with no other abnormal findings matters more than a single number.
What Causes a Low Neutrophil Count
A Recent Viral Infection
A recent viral infection is one common cause of temporary neutropenia, particularly when the low count appears during or shortly after an illness. Viruses such as influenza and Epstein-Barr virus (mononucleosis) are examples of infections that can temporarily lower neutrophil counts. Many infection-related mild neutropenias improve as the illness resolves, but the recovery time varies, so follow-up CBC testing may be needed.
Medications
Several drugs can lower neutrophils, either by slowing bone marrow production or by prompting the immune system to destroy neutrophils early. Chemotherapy is the best known example, and oncology teams expect it and monitor it closely. Outside of cancer treatment, medications that have been linked to lower counts include certain antibiotics such as trimethoprim-sulfamethoxazole, antithyroid drugs such as methimazole, some antipsychotics, and a handful of anti-seizure medications. Clozapine is a well-known example: the FDA notes that information about severe neutropenia remains in a Boxed Warning in the prescribing information and that prescribers should continue to monitor the ANC at the frequencies described there. If you started a new prescription in the weeks before your CBC, mention it to your doctor so they can decide whether it could be involved, and do not stop a prescribed medication on your own.
Autoimmune and Bone Marrow Conditions
In autoimmune neutropenia, the immune system mistakenly targets the body's own neutrophils. It is seen in infants and young children, where it often improves on its own over time, and it can also occur in adults, sometimes alongside other autoimmune conditions. Less commonly, a low count can come from a bone marrow disorder, such as aplastic anemia or a myelodysplastic syndrome, where the marrow itself is not producing enough of one or more blood cell types. These marrow-based causes are much less common than a viral or medication cause, and a single low neutrophil count does not by itself establish them. They often show up alongside other abnormal results on the same CBC, such as low red blood cells or low platelets, rather than a low neutrophil count on its own.
Nutritional Deficiencies
Low vitamin B12, folate, or copper can slow blood cell production in the bone marrow, and neutrophils can be affected along with red cells and platelets. The cause is often correctable once identified. Our guide to What Does a Borderline Low Vitamin B12 Result Mean? covers one of these results in more detail.
How Doctors Investigate a Low Neutrophil Count
The first question your doctor asks is whether this is an isolated finding or part of a bigger pattern. They compare your new result to past CBCs, ask about recent illnesses and new medications, and check whether your red blood cells and platelets are also affected. MedlinePlus notes that an abnormal CBC value does not always mean a condition that needs treatment, because diet, activity level, medicines, and other factors can affect the results. For an otherwise well person with mild, isolated neutropenia, a clinician may recommend repeating the CBC after an appropriate interval, depending on the clinical context and previous results. The European guidelines describe neutropenia as chronic when it lasts longer than three months, and they outline a step-by-step work-up for those cases.
A count that is moderately or severely low, unexplained, or paired with other abnormal cell lines often prompts more testing, such as a peripheral blood smear, tests for autoimmune markers, and sometimes a hematology referral for a bone marrow biopsy. Whether a biopsy is needed depends on the duration and severity of the low count, other blood-count abnormalities, and the suspected cause; the European guidelines note that it might be omitted when mild neutropenia is long-standing, isolated, and stable. If a medication looks like the cause, your prescriber will weigh adjusting the dose, switching drugs, or monitoring more closely; some medications, like clozapine, come with recommended blood count monitoring for this reason. If you take clozapine or another medicine with scheduled blood count checks, keep those checks and tell your prescriber about a low result. Please do not adjust or stop a medication on your own.
Living With a Low Neutrophil Count
If your ANC is only mildly low and your clinician has found no other concerns, you may not need to change your routine. If it is moderately or severely low, especially from chemotherapy or a marrow disorder, your care team may recommend frequent handwashing, avoiding people who are visibly sick, and keeping cuts or scrapes clean and covered. Food-safety precautions should follow your care team's recommendations; the National Cancer Institute advises people in cancer treatment to make sure meat, fish, and eggs are well cooked, but not everyone with a moderately low count needs the same diet.
Fever needs to be read in context. If you are being treated with chemotherapy, have a known ANC below 500, or have another condition that puts you at high risk of infection, a fever can be the only early sign of a serious infection, and it is treated as an emergency. Contact your care team right away and follow the fever plan they gave you. If you cannot reach them promptly, they tell you to come in, or you feel seriously ill, go to the emergency room or call 911.
For people with cancer, the Infectious Diseases Society of America 2010 guideline defines fever during neutropenia as a single oral temperature of 101°F (38.3°C) or higher, or 100.4°F (38.0°C) or higher sustained over one hour, and the ASCO/IDSA guideline recommends that clinicians give patients with febrile neutropenia their first doses of empirical antibiotics within 1 hour of triage. That recommendation applies to febrile neutropenia in the oncology setting, not to everyone with a low ANC. The IDSA guideline also notes that signs and symptoms of inflammation are often attenuated or absent in neutropenic patients, so signs of infection like pus or spreading redness may sometimes be less obvious when neutropenia is significant.
If your count is mildly or moderately low for another reason, a fever or a new sign of infection is still worth a call to your clinician the same day, but it does not automatically mean an emergency room visit. If you have a fever and are not sure how low your count is, call right away rather than waiting. Shaking chills, a racing heartbeat, rapid breathing, confusion, or feeling faint on top of a fever can mean an infection is turning into sepsis and need emergency care. Severe abdominal pain, with or without a fever, can signal a serious infection or another urgent abdominal problem, and a patch of skin that is red, warm, swollen, and spreading quickly is also a reason for emergency care rather than a wait-and-see approach.
Recurring mouth sores or gum infections, new bruising, or unusual fatigue alongside a low count are also worth a visit with your clinician, since they can point to a broader marrow problem or an infection, although they have many other possible causes.
When to Seek Medical Care
When to Seek Urgent or Emergency Care
Because a low neutrophil count can reduce your body's ability to fight infection, signs of infection deserve more attention than they would with a normal count. How urgent they are depends on how low your count is, what is causing it, and whether you are receiving chemotherapy or have another high-risk condition, so a mildly low count with a simple cold does not automatically mean an emergency room visit. This guidance is in addition to, not a replacement for, the general disclaimer above.
Emergency, call 911 or go to the emergency room immediately if:
- A fever of 100.4°F (38.0°C) or higher if you are receiving chemotherapy, have a known ANC below 500, or have another condition that puts you at high risk of infection. Contact your care team right away and follow the fever plan they gave you; go to the emergency room or call 911 if you cannot reach them promptly, they tell you to come in, or you feel seriously ill. Fever can be the only early sign of a serious infection in this situation.
- Shaking chills, a racing heartbeat, rapid breathing, confusion, or feeling like you might pass out, which can signal an infection turning into sepsis.
- Severe abdominal pain, with or without a fever, which can signal a serious infection or another urgent abdominal problem.
- An area of skin that is red, warm, swollen, and spreading quickly, or any wound with pus that is rapidly getting worse.
See a doctor soon (same-day or next available appointment) if:
- A fever, or a new sign of infection such as a sore throat, painful urination, or a cough, if you know your neutrophil count is low but you are not receiving chemotherapy and your count is not severely low. Call your clinician the same day for guidance, and sooner if you feel very unwell. If you have a fever and are not sure how low your count is, call right away rather than waiting, and seek emergency care if you cannot reach anyone.
- A first low neutrophil count with no clear cause, so it can be rechecked and investigated properly.
- Mouth sores or gum infections that keep coming back.
- New bruising, unusual bleeding, or ongoing fatigue alongside a low neutrophil count, which can sometimes point to a broader problem with the bone marrow.
Frequently Asked Questions
What is a normal neutrophil count on a CBC?
Reference ranges vary by lab, age, and inherited factors, but many adult ranges for the absolute neutrophil count (ANC) start at about 1,500 cells per microliter of blood. Your CBC report lists your lab's specific range next to your result. A result just under the range does not always mean a problem, and your clinician will read it alongside your past counts and health history.
Can a low neutrophil count return to normal on its own?
It can, depending on the cause. Many infection-related mild neutropenias improve as the illness resolves, but the recovery time varies, so follow-up CBC testing may be needed. A count that stays low is a reason for a closer look at the cause.
What ANC counts as severe neutropenia?
The European hematology guidelines classify an absolute neutrophil count below 500 cells per microliter as severe neutropenia, the range where infections can progress quickly. In cancer care, the term profound neutropenia is sometimes used for counts below 100. How risky a given count is also depends on its cause and how long it lasts.
Does a low neutrophil count mean I have cancer?
Usually not. A low neutrophil count has many possible causes, including recent infections, medications, immune conditions, nutritional problems, and less commonly bone marrow disorders. A single low result does not by itself mean cancer, and marrow disorders, including certain cancers, are much less common and often come with other abnormal findings on the same CBC.
What medications commonly lower neutrophil counts?
Chemotherapy is the best known cause and is closely monitored during treatment. Outside of cancer care, some antibiotics, antithyroid drugs such as methimazole, certain antipsychotics including clozapine, and a few anti-seizure medications have also been linked to lower counts. Tell your doctor about every medication you take, and do not stop a prescribed medicine on your own.
Should I avoid other people if my neutrophil count is low?
If your count is only mildly low and your clinician has found no other concerns, you may not need to change your routine. If it is moderately or severely low, especially from chemotherapy, your care team may recommend frequent handwashing and avoiding people who are visibly sick. Follow their food-safety advice for your situation.
What is benign ethnic neutropenia?
This is an older name for Duffy-null associated neutrophil count (DANC), also called ACKR1/DARC-associated neutropenia. It is a normal inherited variant that gives some healthy people a lower baseline neutrophil count without an added risk of infection. It is most common in people with African, Middle Eastern, or Arabian Peninsula genetic ancestry, but ancestry alone cannot establish it. Duffy-status testing may help clarify it when the clinical context makes that relevant.
Related articles
Understanding a Complete Blood Count (CBC)High White Blood Cell Count: What It Can MeanLow Platelet Count: Causes and ConcernsSources
- MedlinePlus (NIH) - Complete Blood Count (CBC)
- MedlinePlus (NIH) - Low white blood cell count and cancer
- National Cancer Institute (NIH) - Infection and Neutropenia during Cancer Treatment
- European Hematology Association (PubMed Central, NIH) - The European Guidelines on Diagnosis and Management of Neutropenia in Adults and Children: A Consensus Between the European Hematology Association and the EuNet-INNOCHRON COST Action
- Infectious Diseases Society of America - IDSA 2010 Clinical Practice Guideline Update for the Use of Antimicrobial Agents in Neutropenic Patients with Cancer
- Infectious Diseases Society of America and ASCO - ASCO/IDSA Clinical Practice Guideline Update for Outpatient Management of Fever and Neutropenia in Adults Treated for Malignancy
- American Society of Hematology - Duffy-null Associated Neutrophil Count (DANC)
- FDA - FDA removes risk evaluation and mitigation strategy (REMS) program for the antipsychotic drug Clozapine