The use of magnesium and methanol in the reduction of various functional groups has been well established. In this study, we present a reductive deuteration system using Mg/CH3OD, which successfully facilitates the conversion of α,β-unsaturated esters, amides, and nitriles to their saturated counterparts. This protocol achieves good yields and high degrees of deuterium incorporation, while avoiding defunctionalization in the presence of various functional groups. Our new reductive deuteration system has been thoroughly evaluated and effectively applied to the labeling of dideuterated and tetradeuterated compounds. Notable advantages of this approach include mild reaction conditions, ease of handling, excellent functional group tolerance, selectivity and a cost-effective source of deuterium.