The Neutrophils test is a blood test that measures neutrophils, the most common type of white blood cells. Neutrophils are a key part of the immune system and are often the body’s first responders to bacterial infection and many fungal infections. This test is usually reported as part of a complete blood count (CBC) with differential in a hematology lab.

Your results may be reported in two ways:

• Absolute Neutrophil Count (ANC): the actual number of neutrophils in a specific volume of blood. ANC is often the most clinically useful number, especially when assessing infection risk.
• Neutrophil percentage (%): the proportion of neutrophils among all white blood cells.

In plain language, high neutrophils (neutrophilia) often suggest your body is reacting to an infection, inflammation, physical stress, or certain medications. Low neutrophils (neutropenia) can mean your body has fewer infection-fighting cells than expected, which may raise the risk of infection—especially when the ANC is very low. Your clinician interprets the neutrophil count alongside your symptoms, other blood counts (like total WBC, lymphocytes, hemoglobin, and platelets), and your medical history.

A neutrophils blood test is commonly ordered to help evaluate possible infection, inflammation, immune response, or bone marrow function. It may be done as part of routine care (for example, during an annual physical) or urgently when you are sick.

Doctors often order neutrophils (as part of a CBC with differential) if you have symptoms that could suggest infection or inflammation, such as:

• Fever or chills
• Cough, shortness of breath, or chest symptoms
• Sore throat, sinus symptoms, or ear pain
• Painful urination or urinary frequency
• Skin redness, warmth, swelling, pus, or slow-healing wounds
• Abdominal pain, diarrhea, or other signs of inflammation
• Unexplained fatigue or weakness

This diagnostic test is also commonly used to:

• Monitor chronic conditions that can affect blood cells or inflammation (for example, autoimmune disease).
• Check for medication effects—some drugs can raise neutrophils (like corticosteroids) while others can lower them (some antibiotics, antithyroid drugs, and others).
• Assess bone marrow health when there are abnormal blood counts (low or high white blood cells) or suspicion of a hematology disorder.
• Track infection risk during cancer treatment (chemotherapy, radiation, some immunotherapies). ANC is particularly important for determining neutropenia precautions and timing of treatments.

• Acute bacterial infections (e.g., pneumonia, cellulitis, appendicitis, urinary tract infection)
• Fungal infections (especially in people with weakened immune systems)
• Sepsis (serious, body-wide response to infection)
• Inflammatory and autoimmune conditions (e.g., rheumatoid arthritis, inflammatory bowel disease)
• Bone marrow disorders (e.g., aplastic anemia, myelodysplastic syndromes)
• Blood cancers and hematology conditions (e.g., leukemia, myeloproliferative neoplasms)
• Medication-related neutropenia (drug-induced low neutrophils)
• Viral illnesses that can lower neutrophils (transient neutropenia with some viral infections)
• Nutritional deficiencies associated with low white blood cells (e.g., vitamin B12 or folate deficiency)

• Detecting and monitoring infection early, especially suspected bacterial infection
• Assessing immune system status and infection risk (e.g., neutropenia screening and follow-up)
• Monitoring inflammation as part of overall health evaluation (with other markers and symptoms)
• Medication safety monitoring for drugs that can affect white blood cells
• Supporting cancer care monitoring (chemotherapy-related neutrophil drops and recovery)
• General wellness checkups as part of a CBC blood test and routine preventive care
• Evaluating unexplained fever, fatigue, or recurrent infections with a diagnostic blood test