It is well known that the effect of laser irradiation on the blood causes a change in the shape of red blood cells and an increase in their activity, especially in low-level laser therapy (LLLT). The aim of this study was to identify the ability of erythrocytes to deform when exposed to a blue laser.24 laboratory rats were exposed to blue laser in the gingival region of the lower jaw daily for 5 minutes over 3 days. The blue laser possessed a power of 0.5 W and was operated using a con-tactless approach, the dynamic technique in continuous wave mode, and an uninitiated fiber. A blood sample was taken from the lateral vein of the tail before the LLLT, on the first, second, third, and fifth days. The samples were stained, and cytometry was conducted. The exposure to blue laser caused a significant increase in the number of dome-shaped deformable erythrocytes in the blood of laboratory rats (p