Abstract: A method of quantization of magnetic nanoparticle absorption in animal tissues includes determination of the number of magnetic nanoparticles absorbed in animal tissues by magnetization measurements. The method is based on the measurement of magnetization versus magnetic field applied of the tissue sample absorbed with the nanoparticles obtaining their saturation magnetization. This magnitude is compared to the saturation magnetization of the same nanoparticles found in the tissue for the determination of the absolute number of magnetic nanoparticles in the animal tissue studied. The method includes preparing the samples for the sample holder, measuring the magnetization vs. applied magnetic field of a known number of magnetic nanoparticles, determining the saturation magnetization of the sample to be studied by measuring the magnetization and calculating the nanoparticle mass in the tissues from the data measured (saturation magnetization of the sample and of calibration of nanoparticles).