NMNH (dihydronicotinamide mononucleotide) is a reduced form of NMN - it differs in that it has an extra hydrogen on the nicotinamide moiety (analogous to NADH vs. NAD+). This minor chemical change leads to different biochemical dynamics. In the body, normal NMN (nicotinamide mononucleotide) is metabolized within the NAD+ salvage pathway to NAD⁺ (the oxidized form), whereas NMNH is the precursor of the reduced form of NADH. The key enzyme is nicotinamide mononucleotide adenylyltransferase (NMNA