Sepsis is a potentially fatal condition that occurs when an infectious agent, such as bacteria, gets in a person's bloodstream. The infection affects the immune system, which then triggers a reaction that can cause uncontrolled inflammation in the body1 . All blood components may present the contamination. Once inoculated bacteria in a blood component, it can proliferate rapidly reaching high levels within few hours and, in a short period, it may lead to several basal changes in the individual and even death2 . Studies have shown an increase in the incidence of sepsis over the years, and it is mainly due to the growing resistance of microorganisms to antibiotics since these drugs are still sold and used improperly3 . The photodynamic inactivation (PDI) has been one of the most promising alternatives for microbiological control and other diseases. Its principle of action is based on a photosensitizer (PS) activated by light at the correct wavelength to oxidize organic substrates, resulting in cytotoxic effects4,5. The technique is being applied to a large variety of microorganisms and decontaminating blood. Some studies have investigated the action of PDI in blood6–9, and even then, there is a need to understand better what happens when we apply PS and light in blood in an attempt to eliminate the microorganisms. Photogem is a hematoporphyrin derivative that has been used with success in many clinical cases such as skin cancer and inactivation of bacteria10,11. Previous studies have shown that PDI using Photogem as a photosensitizing molecule is a good alternative for blood decontamination12,13. In the previous studies were observed hemolysis when red blood cells (RBCs) were submitted to PS concentration and light dose tested. This study has been conducted to further understand through absorption spectroscopy and fluorescence confocal microscope the PS-blood interaction. This is important because the PDI damage needs to be restricted to the bacteria and the blood functions should be preserved.