White blood cells (WBCs) are essential components of the body’s immune system, defending against various threats. Corticosteroids, a widely prescribed class of medications, have potent anti-inflammatory and immunosuppressive properties. This article explores the relationship between corticosteroids and white blood cell levels, addressing a common question about their effect on WBC counts.
Understanding White Blood Cells and Steroids
White blood cells, also known as leukocytes, are the body’s primary defense against infections and inflammation. These cells circulate throughout the bloodstream and tissues, identifying and neutralizing foreign invaders like bacteria and viruses. They collectively contribute to the immune response.
Corticosteroids, such as prednisone or hydrocortisone, are synthetic hormones mimicking cortisol, naturally produced by the adrenal glands. Doctors prescribe these medications for conditions like autoimmune disorders, allergic reactions, and inflammatory diseases. Their main action involves reducing inflammation and suppressing an overactive immune system.
The Steroid-WBC Connection: Why the Increase?
Corticosteroids typically lead to an increase in the total white blood cell count. This elevation is predominantly due to a redistribution of neutrophils, which are an abundant type of white blood cell. These neutrophils normally adhere to the inner walls of blood vessels, a process known as margination, and are not freely circulating for immediate detection.
When corticosteroids are administered, they cause these “marginalized” neutrophils to detach from the vessel walls and enter the main circulating bloodstream. This process, termed “demargination,” makes a greater number of neutrophils available for detection in a standard blood test, resulting in a higher measured count. This increase does not signify an enhanced production of new white blood cells; rather, it reflects a temporary shift in the location of existing neutrophils within the body’s vascular system. This rapid shift can lead to a noticeable jump in the measured white blood cell count within hours.
While the total white blood cell count rises, other types of white blood cells, such as lymphocytes and eosinophils, may show a decrease in their circulating numbers. Corticosteroids can suppress the migration of lymphocytes from the bloodstream into lymphoid tissues, reducing their presence in the blood. Similarly, these medications can cause eosinophils to move out of circulation into tissues or accelerate their destruction. Despite these specific decreases, the substantial rise in neutrophils results in an overall higher total white blood cell count.
Clinical Implications and What to Expect
The increase in white blood cells due to corticosteroid use, often referred to as “steroid-induced leukocytosis,” is a common and anticipated side effect. This elevation generally does not indicate an underlying infection or other serious medical issue. Healthcare providers are aware of this effect and consider it a normal response to the medication.
This steroid-induced rise in white blood cell count is typically temporary. The count usually returns to its baseline levels once the corticosteroid treatment is completed or the dosage is gradually reduced. The duration of the elevation can vary depending on the steroid dosage and length of treatment, but it generally resolves within days to weeks after discontinuation.
Doctors differentiate this expected steroid effect from a true infection by evaluating other clinical signs and symptoms. For instance, a patient with an infection might exhibit fever, localized pain, or other specific indicators of illness, which would not be present with steroid-induced leukocytosis alone. Additional laboratory tests, such as C-reactive protein levels or specific white blood cell differentials, may also help distinguish between these two scenarios.
While steroid-induced leukocytosis is a normal response, individuals taking corticosteroids should still consult their doctor if they have any concerns about their health. It is important to seek medical advice if new symptoms develop, especially those suggestive of an infection, as steroids can sometimes mask the typical signs of illness or increase susceptibility to infections. Open communication with a healthcare provider ensures proper interpretation of blood test results.