Neutrophils Test: Meaning, Normal Range, Low & High Neutrophils Causes, Symptoms, and Complete Medical Guide
What Is the Neutrophils Test?
The Neutrophils Test measures the number or percentage of neutrophils present in your blood. Neutrophils are a type of white blood cell (WBC) and are one of the most important defenders of the immune system. They are usually the first cells to respond when an infection—especially a bacterial infection—enters the body. Because they react quickly, their levels often change early during illness, inflammation or immune disorders.
This test is included in a Complete Blood Count with Differential (CBC with diff). A differential report shows the breakdown of all types of white blood cells, helping doctors understand whether the body is fighting an infection, experiencing inflammation, or facing a bone marrow–related issue.
Where Are Neutrophils Produced?
Neutrophils are produced inside the bone marrow from hematopoietic stem cells. These stem cells mature into large precursor cells that eventually form neutrophils. Once fully developed, they are released into the bloodstream and continuously circulate throughout the body.
Neutrophils are part of the body’s innate immune system, which is the rapid-response defense mechanism. They do not need prior exposure to a germ to react. The moment an infection appears, neutrophils quickly migrate to the affected area to destroy harmful organisms. Their lifespan is short—usually only a few hours to a few days—so the bone marrow must produce them constantly to maintain adequate levels.
Functions and Importance of Neutrophils
Neutrophils are essential for daily immune protection. They perform several critical defense roles that keep infections under control.
Destroy Bacteria and Fungi
Neutrophils quickly attack bacteria and certain types of fungi by recognizing them as foreign invaders. They act rapidly to prevent infections from spreading.
Phagocytosis
One of their most important functions is phagocytosis. Neutrophils engulf (or “eat”) harmful microorganisms, break them down, and remove them from the body. They also clean up dead tissue and debris.
Inflammation Response
When an infection or injury occurs, neutrophils release chemicals that create inflammation. This process helps isolate the infection, increase blood flow to the area, and begin tissue repair.
Forming Pus
Neutrophils die after fighting infections, and their dead bodies often accumulate as pus. This is why infections with a lot of neutrophil activity produce pus-filled areas.
Without an adequate number of neutrophils, the body becomes vulnerable. Even a small infection can quickly turn serious if neutrophils are too low.
Causes of Low Neutrophils (Neutropenia)
A low neutrophil count is known as neutropenia. When levels fall too low, the body cannot defend itself against infections effectively.
Severe Infections
Serious or long-lasting infections can exhaust the bone marrow, reducing its ability to produce neutrophils.
Bone Marrow Disorders
Conditions such as leukemia, aplastic anemia, and myelodysplastic syndromes affect the bone marrow’s ability to create healthy blood cells.
Chemotherapy or Radiation
Cancer treatments destroy rapidly dividing cells, including those in the bone marrow. This is why neutropenia is common in patients receiving chemotherapy.
Autoimmune Diseases
Diseases like lupus or rheumatoid arthritis may cause the immune system to attack neutrophils or bone marrow cells that produce them.
Vitamin B12 or Folate Deficiency
These vitamins are necessary for forming blood cells. Deficiency can impair neutrophil production.
Genetic Disorders
Some individuals are born with conditions such as congenital neutropenia that reduce neutrophil formation.
Medications
Certain antibiotics, antipsychotics, and drugs used to suppress immunity can lower neutrophil levels.
Symptoms of Low Neutrophils
Because neutrophils are key defenders, low levels make infections more frequent and more severe. Symptoms may include:
- Recurrent infections
- Fever or chills
- Mouth ulcers or painful sores
- Persistent sore throat
- Slow or poor wound healing
- Constant fatigue
- In severe neutropenia, infections may appear suddenly and worsen rapidly
People with very low neutrophil counts need urgent medical attention because infections can become life-threatening.
Causes of High Neutrophils (Neutrophilia)
High neutrophil levels are called neutrophilia. This often happens when the body is responding to stress, infections, inflammation or injury.
Bacterial Infections
Conditions like pneumonia, urinary tract infections or skin infections commonly increase neutrophil levels.
Inflammatory Disorders
Diseases such as rheumatoid arthritis or inflammatory bowel disease trigger inflammation that raises neutrophil counts.
Physical or Emotional Stress
Events such as surgery, injury, intense anxiety or heavy physical activity may temporarily increase neutrophil numbers.
Smoking and Heavy Exercise
Smoking causes chronic irritation and inflammation, leading to higher neutrophil counts. Intense exercise temporarily boosts levels as well.
Injury or Burns
The body releases more neutrophils to protect and repair tissues after trauma.
Certain Cancers
Leukemia and other blood cancers may cause uncontrolled production of neutrophils.
Medications
Steroids, lithium, and some anti-inflammatory drugs raise neutrophil levels as part of their effect on the immune system.
Symptoms of High Neutrophils
Most individuals with high neutrophil levels do not feel specific symptoms. Any symptoms that appear usually depend on the underlying cause.
Common signs associated with the cause of neutrophilia include:
- Fever
- Body pain
- Swelling or inflammation
- Redness around infected areas
- Fatigue
- In leukemia: recurrent infections, unexplained bruising, night sweats
The WBC count in a CBC report typically shows elevated levels alongside high neutrophils.
Neutrophil Reference Ranges
Although exact ranges may vary between laboratories, the typical levels are:
Absolute Neutrophil Count (ANC)
- Normal: 1,500 – 8,000 cells/µL
- Mild Neutropenia: 1,000 – 1,500
- Moderate Neutropenia: 500 – 1,000
- Severe Neutropenia: <500 (dangerous)
Neutrophil Percentage (CBC Differential)
- Adults: 40% – 70% of total WBCs
- Children: 30% – 60%
Doctors use both the percentage and ANC value to evaluate immune function accurately.
Sample Type and Collection
- Sample Required: Whole blood
- Collection Tube: Lavender-top EDTA tube
A blood sample is taken from a vein in the arm. The neutrophil count is calculated automatically as part of a CBC with differential. Results are usually available within the same day.
Test Preparation
- No fasting is required.
- Stay hydrated before the test.
- Avoid heavy exercise immediately before testing because it may temporarily raise neutrophil levels.
- Inform your doctor if you are taking steroids, chemotherapy drugs, or medications that affect immunity.
- Tell your doctor about ongoing infections or fevers.
When to Consult a Doctor
You should consult a doctor if:
- You experience frequent or unusual infections
- You notice mouth ulcers, fever or sore throat without a clear cause
- Your CBC repeatedly shows low or high neutrophils
- You are undergoing chemotherapy or immune-suppressing treatments
- You have autoimmune diseases such as lupus or rheumatoid arthritis
- You notice delayed wound healing or recurring skin infections
Early evaluation ensures proper diagnosis and prevents complications related to infections or bone marrow disorders.
Important Word Explanations
- Neutrophils: White blood cells that provide rapid defense against bacteria and fungi.
- Neutropenia: Low neutrophil count leading to high infection risk.
- Neutrophilia: High neutrophil count often due to infection, inflammation or stress.
- ANC (Absolute Neutrophil Count): Actual number of neutrophils per microliter of blood.
- CBC with Differential: A blood test that measures all types of white blood cells.
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