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The interaction of hydrogen with the core and the strain field of edge dislocations is studied using a multiscale approach. We have therefore developed a combined thermodynamic and analytical model with full atomistic resolution that allows to quantify the local hydrogen concentration around the dislocation core as a function of temperature and hydrogen chemical potential. This model takes, as input, information from atomistic calculations, such as hydrogen–hydrogen interaction and the dislocation core structure, and faithfully reproduces results from a computationally much more expensive fully atomistic approach that combines the Embedded Atom Method with Monte Carlo simulations. The onset of nano-hydride formation and with it the activation of hydrogen enhanced local plasticity (HELP) is predicted through a parametric study of the hydride size as a function of temperature and bulk hydrogen concentration. The study reveals a sharp transition between hydride forming and non-hydride forming regimes. The transition between these two regimes corresponds to a critical hydrogen chemical potential μ^c_H related to the nano-hydride nucleus of the system.