Direct hydrogen isotope exchange represents a distinctive strategy for deuterium labelling, where the protium is directly replaced by deuterium. In this graphic review, we summarized the progress in deuteration via transition metal catalyzed hydrogen isotope exchange. The review was organized according to the mechanism of C-H bond activation in the homogeneous catalysis, and the heterogeneous catalysis was also discussed according to the catalyst type. Representative mechanistic processes were depicted, and proven cases for tritiation were also highlighted.