Neutrophils (Absolute)

Inherited variation: A stable low count can reflect the Duffy-null (ACKR1) phenotype, which usually does not increase infection risk. Prior counts and the clinical context help distinguish this from acquired neutropenia.

Recent infection or medications: Viral illnesses can temporarily suppress neutrophils. Some antibiotics, antithyroid drugs, clozapine, immunosuppressants, and chemotherapy can also lower the count.

Nutrient deficiencies: Vitamin B12, folate, or copper deficiency and severe undernutrition, often accompanied by other blood-count abnormalities.

Less common: Autoimmune disease, an enlarged spleen, bone marrow disorders, or congenital neutropenia. Persistent unexplained reductions warrant further assessment.

Infection and inflammation: Bacterial infections, inflammatory disorders, tissue injury, and recent surgery commonly raise neutrophil counts.

Lifestyle and temporary changes: Smoking and obesity can contribute to persistent mild elevations. Strenuous exercise and physical or emotional stress can cause temporary increases.

Medications: Corticosteroids, beta-agonists, lithium, and granulocyte colony-stimulating factors can increase circulating neutrophils.

For women: Pregnancy commonly raises neutrophil counts and requires pregnancy-specific reference intervals.

Less common: Previous splenectomy or myeloid blood disorders. Persistent unexplained elevations, especially with immature cells or other blood-count abnormalities, warrant further assessment.