Reduced nicotinamide adenine dinucleotide (NADH) can generate a ruthenium-hydride intermediate that catalyzes the reduction of O2 to H2O2, which endows it with potent anticancer properties. A catalyst that could access a Ru-H intermediate using oxidized nicotinamide adenine dinucleotide (NAD+) as the H- source, however, could draw upon a supply of reducing equivalents 1000-fold more abundant than NADH, which would enable significantly greater H2O2 production. Herein, it is demonstrated, using the reduction of ABTS•- to ABTS2-, that NAD+ can function as a reductant. Mechanistic evidence is presented that suggests a Ru-H intermediate is formed via β-hydride elimination from a ribose subunit in NAD+. The insight gained from the heretofore unknown ability of NAD+ to function as a reductant and H- donor may lead to undiscovered biological carbohydrate oxidation pathways and new chemotherapeutic strategies.