Almost nothing, in people. NAD+, nicotinamide adenine dinucleotide, is a cofactor that cells need for a long list of metabolic reactions [4]. The case for a nasal form rests on the broader idea that the nose can carry some drugs into the body and even the brain [2]. No human trial of an NAD+ nasal spray has been published. The evidence that exists is a mouse study, a general literature on nasal drug delivery, and human data for other routes that show how hard NAD+ is to raise from outside. On this site NAD+ sits under the longevity goal.
The one intranasal NAD study
A 2026 study tested intranasal NAD for loss of smell [1]. In cultured human olfactory stem cells, NAD pushed the cells to mature into smell-sensing neurons, with higher levels of the marker genes that define them. In mice whose sense of smell had been destroyed with a zinc sulfate solution, NAD given through the nose improved smell function on behavioral tests and repaired the lining of the olfactory tissue, compared with a salt solution.
That is a real finding, and a narrow one. It concerns repairing smell tissue damaged by a chemical, in mice, where the spray lands directly on the tissue being measured. It says nothing about energy, aging, or the brain in people.
What the nose can and cannot do as a route
A 2026 review of the clinical evidence for nose-to-brain delivery describes the idea: some drugs given through the nose can reach the brain directly, bypassing the blood-brain barrier [2]. FDA-approved nasal products exist for seizures and migraine, which shows the route can work for the right molecule. The same review says well-designed clinical studies are still needed to establish long-term safety and effectiveness, and notes that results improve with special formulations and devices built to reach the smell region.
Whether NAD+ is one of those molecules has not been measured in people. No study has reported blood or brain NAD+ levels after a nasal dose.
Where the human data are: oral precursors
The strongest human evidence on raising NAD+ comes from swallowed building blocks rather than NAD+ itself. In a randomized, placebo-controlled study of 65 healthy adults, 14 days of nicotinamide riboside (NR) or nicotinamide mononucleotide (NMN) comparably raised NAD+ in the blood, while plain nicotinamide did not [4]. The authors propose that gut bacteria convert NR and NMN into nicotinic acid, which then drives the rise. Raising a blood level is not the same as a health benefit, and the study did not test one.
Regulatory status
Nicotinamide adenine dinucleotide is in Category 1 of the FDA’s list of bulk substances nominated for 503A compounding, the substances under evaluation, in the version updated May 14, 2026 [5]. The listing is not limited by route. Being compoundable is a regulatory status, not evidence that a nasal form works.
For how injectable forms are prepared from powder, see how to reconstitute peptides. A related longevity molecule with its own delivery questions is covered in glutathione injections, and a mitochondrial peptide often mentioned alongside NAD+ in what the research shows on MOTS-c.