There are a few ways to increase NAD+ levels. NAD+ precursors are one. This is where nicotinamide mononucleotide (NMN) and nicotinamide riboside Chloride (NRC) come into the picture. Here's a quick (and less science-y) breakdown of why we use NRC instead of NMN: NR can enter cells, NMN can’t. NMN must turn into NRC before it can enter a cell There are human clinical trials to prove NR increases NAD+ levels in humans. NMN’s only published trials are in rats and mice. NR is taken orally, NMN is mostly studied via intravenous injection (IV). 12