This work addresses hydrogen-induced failure by examining how hydrogen distributes within metallic microstructures and concentrates at critical features. Hydrogen distribution is controlled by concentration gradients, stress fields, and microstructural inhomogeneities, all of which are strongly influenced by forming, processing, and heat treatment. A microstructure-based modelling framework is presented to link these factors to hydrogen behaviour in fasteners. The approach employs a thermodynamic diffusion and trapping model that transfers microstructural information to the component scale. Key microstructural features—grain boundaries, dislocations, and precipitates—act as energetically favourable hydrogen trap sites, each defined by a trap density and trapping energy. While trapping energies are often available in the literature, directly relating measurable microstructural parameters (e.g. grain size, dislocation density, precipitate morphology) to trap densities is challenging. This is addressed through a geometrical, microstructure-based estimation of effective trap densities, which are then combined with literature trapping energies. The modelling framework is validated using thermal desorption spectroscopy (TDS) data and further integrated with a forming process simulation in DEFORM and a finite-element hydrogen diffusion model in ABAQUS. Results show that hydrogen distribution after forming is mainly governed by deformation and dislocation density gradients. After heat treatment, hydrogen gradients are largely homogenised, with grain boundaries and precipitates becoming the dominant trapping sites. During service, stress gradients and plastically deformed regions act as preferred hydrogen trapping locations. Overall, the framework provides an integrated numerical perspective linking microstructure, processing, and service conditions, offering a complementary alternative to extensive experimental testing and a valuable tool for designing hydrogen-resistant materials and components.