Photoluminescence spectra of the up-conversion nanoparticles NaYF4 : Y³⁺, Er³⁺ arranged under a layer of an adipose tissue have been recorded in a wide temperature range. It is shown that if nanoparticle temperature is determined from the photoluminescence spectra, an error arises related to spectrum distortion due to light scattering in a sample. A correction algorithm for reducing this error is developed