What this marker measures
Neutrophils normally make up 45–70% of all white blood cells. During severe bacterial infections the count rises dramatically in a pattern called a "left shift."
High or low: what it can mean
High Neutrophils
Elevated neutrophils most commonly signal a bacterial infection or tissue inflammation. Physical stress, corticosteroid use, and smoking can also raise the count.
Read full explanation →
Low Neutrophils
Low neutrophils (neutropenia) may reduce the body's ability to fight bacterial infections. This can result from viral infections, certain medications, or conditions affecting white blood cell production.
Read full explanation →
Frequently asked questions
What is Neutrophils?
+
Neutrophils are the most abundant white blood cell and the immune system's first responders, engulfing and destroying bacteria and fungi.
What does Neutrophils measure?
+
Neutrophils normally make up 45–70% of all white blood cells. During severe bacterial infections the count rises dramatically in a pattern called a "left shift."
What does high Neutrophils mean?
+
Elevated neutrophils most commonly signal a bacterial infection or tissue inflammation. Physical stress, corticosteroid use, and smoking can also raise the count.
What does low Neutrophils mean?
+
Low neutrophils (neutropenia) may reduce the body's ability to fight bacterial infections. This can result from viral infections, certain medications, or conditions affecting white blood cell production.
Related biomarkers
Editorial note
LabTestly explains lab markers using plain-English educational content. Reference ranges may vary by laboratory and should be interpreted with a clinician.
Educational content · Editorially reviewed for clarity · Last updated
Common sources used for lab-test education
Not medical advice
This page is for general understanding only and does not replace medical advice from your clinician. Reference ranges can vary by laboratory, age, sex, pregnancy status, medications, and clinical context.