Neutrophils are a type of white blood cell (leukocyte) that plays a significant role in the immune system. They are a primary defense, actively seeking and destroying invaders like bacteria and fungi. Produced continuously in the bone marrow, an average healthy adult generates over 100 billion daily. Their presence in the bloodstream indicates the body’s immediate response to infection or injury.
Understanding Your Neutrophil Count
Neutrophil counts are often presented in two ways: as a percentage of total white blood cells and as an absolute neutrophil count (ANC). The percentage, such as “neutrophils 65,” indicates they make up 65% of all white blood cells in your sample. Neutrophils typically account for 50% to 70% of all white blood cells in healthy adults, so a 65% reading generally falls within the expected range.
The absolute neutrophil count (ANC) provides the exact number of neutrophils per microliter of blood. This is calculated by multiplying your total white blood cell count by the percentage of neutrophils. For example, if your total white blood cell count is 8,000 cells/mcL and your neutrophils are 65%, your ANC would be 5,200 cells/mcL (8000 x 0.65). The normal ANC range for a healthy adult is typically between 2,500 and 7,000 cells per microliter. An ANC of 5,200 cells/mcL would therefore be considered healthy.
Laboratory reference ranges can vary slightly between facilities. A single number, such as 65%, is just one piece of information. Interpreting this result requires considering your overall health, any symptoms, and other blood test results.
Why Neutrophil Levels Can Be High
An elevated neutrophil count, called neutrophilia, means your body is producing more neutrophils than usual. This often indicates your immune system is responding to a threat. Bacterial infections are a common cause, as neutrophils target and eliminate bacteria.
Inflammation, from conditions like arthritis or tissue damage, can also increase neutrophil levels. Physical or emotional stress triggers stress hormones, temporarily elevating neutrophil counts. Certain medications, particularly corticosteroids, can increase neutrophil production as a side effect. Less commonly, blood disorders like myeloproliferative neoplasms can result in persistently high neutrophil levels due to unregulated cell production in the bone marrow.
Why Neutrophil Levels Can Be Low
A low neutrophil count, known as neutropenia, means your body has fewer neutrophils than expected. This can reduce your ability to fight off infections. Viral infections, such as influenza or mononucleosis, can temporarily suppress bone marrow activity, leading to a drop in neutrophil production.
Certain medications are a common cause of neutropenia, including chemotherapy drugs and some antibiotics. Autoimmune diseases, where the immune system mistakenly attacks healthy cells, can target and destroy neutrophils. Problems with the bone marrow, such as aplastic anemia or certain cancers like leukemia, can impair their production. In severe infections, neutrophils may be consumed faster than they can be produced, leading to a temporary decrease in their circulating numbers.
Next Steps and When to Talk to Your Doctor
A healthcare professional should interpret your lab results, including your neutrophil count, in the context of your medical history and current health status. They will consider your symptoms, other blood test results, and any pre-existing conditions. If your 65% neutrophil count, or corresponding absolute neutrophil count, falls outside your lab’s normal range, or if you are experiencing symptoms, a medical consultation is warranted.
Symptoms that might prompt a discussion with your doctor include unexplained fever, persistent fatigue, frequent or unusual infections, swollen lymph nodes, or sores that do not heal. These signs could suggest an underlying issue affecting your neutrophil levels. Your doctor might recommend additional tests, such as a complete blood count (CBC) with differential, or further monitoring to understand the cause and determine the appropriate course of action.