A method of determining calciotropic activity of a preparation of algae of the genus Padina pavonica. The algae preparation may be in the form of a powder or an extract. The method consists of culturing human or animal osteoblasts in a culture medium containing calcium ions in a well plate. The preparation is added thereto and non-fixed calcium ions are eliminated in the culture medium. Further, the culture medium is acidified to destroy an extracellular matrix formed by the osteoblasts in the culture medium. Thereafter, filtering of the culture medium is carried out and then a concentration of fixed calcium ions in the osteoblasts is determined and compared with a calibration scale of a known activator of the fixation of calcium or in the presence of an inhibitor of the fixation of calcium or both.