The presented work provides values of Mean Excitation Energy (MEE) for all atoms and their ions with atomic numbers $1\le Z\le 86$. To fill in the gaps in the available data, we propose an approximate atomic model for ions of high-Z elements, that uses a semi-empirical formula based on the Local Plasma Approximation (LPA). Despite the fact that the LPA, in its original form, poorly predicts MEE for high ionization states, a relatively simple modification utilizing a fit function can amend this shortcoming. We assess the importance of relativistic effects for the MEE for highly ionized atoms and compare the proposed formula to other approximations available for high-Z elements. We estimate the uncertainty of the presented data to be less than 40% in absolute value for the worst cases and less than 20% for most ions. This corresponds to an uncertainty of the order of few percent for the logarithm of MEE, which is the value of interest in the case of Bethe’s theory of stopping power.