The interaction of laser light with biological samples acquires increasing importance due to its numerous applications in areas like optogenetics or biophotonics. For many of these applications, it is important to know how light interacts with biological material, if it’s possible to quantify absorption and scattering effects produced and if these effects are local. A useful label-free technique for this purpose is digital holographic microscopy (DHM) that allows to obtain spatial images of living cells being irradiated in real time in a quantitative way, with no contact with cells and with robustness, stability and a rapid data acquisition. The main objective of this work is to perform a quantitative study on laser irradiation of hippocampal cells using digital holographic microscopy. To carry out this study, unlabeled cells samples have been irradiated by low-power continuous lasers of 405 and 785 nm wavelength. The modifications of optical path length (OPL) produced by the interaction have been measured using digital holographic microscope. According to the study conditions, it is shown that the evolution of OPL values is different depending on the irradiated area of the sample, laser power is a factor to consider depending on the wavelength of the laser used, both the OPL values differ and absorption effects occur depending on the laser wavelength used. These findings represent a first step towards the development of a protocol that can be used in the study of light-cell interaction processes using digital holographic microscopy.