Nicotinamide adenine dinucleotide Nicotinamide adenine dinucleotide ( NAD) is a coenzyme central to metabolism. [3] Found in all living cells, NAD is called a dinucleotide because it consists of two nucleotides joined through their phosphate groups. One nucleotide contains an adenine nucleobase and the other, nicotinamide. .

what is nad in medical terms