Nicotinamide riboside (NR) is a form of vitamin B3. There is interest in using NR supplements to increase NAD+ levels in the body with minimal side effects. Suggested Dose: In a GRAS (generally recognized as safe) notice for Niagen, the Food and Drug Administration (FDA) suggested an upper limit (UL, an amount not to be exceeded) of 180 milligrams (mg) per day for a person weighing 60 kilograms (kg), equivalent to 132 pounds.