The concentration depth profiles of hydrogen isotopes implanted into titanium carbide (TiC^x) specimens in the composition range of x = 0.50 to 0.96 have been measured using the elastic recoil detection analysis. The retention behavior of the implanted deuterium changes with the specimen composition; the deuteriums deposit near the projected range, and a saturation is eventually reached for the specimens with the composition close to stoichiometric TiC, while for the specimens with off-stoichiometric compositions they diffuse very fast away from the near surface region to the interior to attain the saturation. The experimental data of retention and isotopic replacement are compared with a simple model of local saturation and replacement.