Nicotinamide riboside (NR) has been available over the counter as a nutraceutical (Niagen®, ChromaDex, Inc.) since the summer of 2013. However, classical pharmacokinetic (PK) data for NR have not been reported in humans. This study will use a recently-developed, whole blood assay for NR to assess the pharmacokinetics of NR at a maximum dose of 1000 mg twice daily, and will collect history, physical examination and laboratory data to determine the safety and tolerability of NR in eight, healthy volunteers. In addition, whole blood nicotinamide adenine dinucleotide (NAD) levels will be measured at each time point, to determine whether this NR dose significantly raises whole blood NAD levels.