Taking NAD+ orally is not a good idea. Almost all NAD+ is broken down in the stomach and in the gut, while NAD+ in itself is too large a molecule to be absorbed by the gut into the bloodstream. Therefore, NAD+ can be best delivered intravenously. The problem with NAD+ infusions is that one suddenly gets a very high NAD+ peak in the blood, which comes down very quickly and is not ideal. Also, NAD+ infusions are not given continuously, but only on an irregular basis (every few weeks or so). It's better to boost your NAD+ levels on a continuous, daily basis.
Therefore, instead of NAD+, we advise taking NMN, which is absorbed in the gut and is also stable in the bloodstream so it can increase NAD+ levels.