From the Research
Yes, white blood cell count can increase after a blood transfusion, as evidenced by a study published in 2004 1, which found that transfusion of non-filtered packed red cells may frequently cause an acute and transient leukocytosis in critically ill nonseptic patients. This phenomenon occurs through several mechanisms, including the transfused blood product itself containing white blood cells, especially if it's not leukoreduced, and the recipient's body mounting an inflammatory response to the transfused blood, triggering white blood cell production. The study found that the white blood cell count in nonseptic patients increased from 14.3 +/- 4.8 before transfusion to 19.5 +/- 7.0 2 hrs following transfusion (p <.001) and returned to baseline in 24 hrs 1. Additionally, the study suggested that interleukin-8 accumulating in stored non-filtered packed red cells may play a role in this phenomenon, as the concentrations of interleukin-8 were higher in units that caused leukocytosis in the recipients compared with those that did not (408.4 +/- 202 vs. 65.1 +/- 49, p =.02) 1. It's worth noting that most modern blood products are leukoreduced to minimize these reactions, but temporary white count elevations can still occur within hours to days after transfusion, as discussed in a study published in 2016 2. However, the most recent study available, published in 2025 3, although not directly related to blood transfusions, highlights the importance of considering other factors that may cause leukocytosis, such as corticosteroid use. In the context of blood transfusions, the key takeaway is that a transient increase in white blood cell count after transfusion is a recognized phenomenon, and clinicians should be aware of this when interpreting laboratory results in patients who have received blood transfusions.