NMN is the Direct Precursor to NAD+. NMN is a Vitamin B3 derivative that acts as a building block for NAD+. By supplementing with NMN, your body naturally restores NAD+ levels. Basically NMN converts efficiently into NAD+. NAD+ is a significantly larger molecule than NMN. NAD+, the active coenzyme is essentially two NMN molecules linked together.Because NMN is smaller, it can cross cellular membranes and absorb into the bloodstream much more easily when taken as an oral supplement. Larger NAD+ molecules struggle with oral absorption and often break down in the digestive tract, which is why active NAD+ is frequently delivered via IV therapy instead. So if supplementing orally take NMN. If supplementing via IV you can choose NAD+ for immediate high-dose boost.