The rate of energy transfer from ion projectiles onto the electrons of a solid target is hard to determine experimentally in the velocity regime between the adiabatic limit and the Bragg peak. First-principles simulations have lately offered relevant new insights and quantitative information for prototypical homogeneous materials. Here we study the influence of structural anisotropy on electronic stopping power with time-dependent density functional theory simulations of a hydrogen projectile in graphite. The projectile travelled at a range of angles and impact parameters for velocities between 0.1 and 1.4 a.u., and the electronic stopping power was calculated for each simulation. After validation with average experimental data, the anisotropic crystal structure was found to have a strong influence on the stopping power, with a difference between simulations parallel and perpendicular to the graphite plane of up to 25%, more anisotropic than expected based on previous work. The velocity dependence at low velocity displays clear linear behaviour in general, except for projectiles travelling perpendicular to graphitic layers, for which a threshold-like behaviour is obtained. For projectiles travelling along graphitic planes metallic behaviour is observed with a change of slope when the projectile velocity reaches the Fermi velocity of the electrons.