Evidence ledger / NAD+ due diligence
NAD+ is sold as a supplement, not a drug — here is what the human evidence honestly shows.
A transparency-first readout of the controlled human trials: what raising NAD+ has actually been measured to do, what stays unproven, and where the IV-route quality risk really sits. Every figure cited.
The honest version
NAD+ (nicotinamide adenine dinucleotide — a fuel-handling helper molecule every cell uses to turn food into energy) is not a drug and not a single product on a shelf. It is a coenzyme (a helper molecule an enzyme needs to do its job) your body already makes, and its levels fall with age. Most things sold as "NAD+" are actually precursors (building blocks the body converts into NAD+ — NMN and NR are the common ones), because NAD+ itself is too large to absorb well by mouth. In human trials, oral NMN and NR reliably raise blood NAD+. Whether that produces a real health benefit in people is the open question this page is honest about.
What the human trials have measured
NAD+ is a dinucleotide coenzyme found in every living cell, where it carries electrons through energy metabolism and is consumed as a substrate by signaling enzymes [5]. Tissue NAD+ declines with age, which is the entire rationale behind the supplement market built around it [5]. The honest headline from the controlled human record is narrow but real: oral precursors raise blood NAD+, dose-dependently and reproducibly.
Nicotinamide riboside (NR) at 100, 300, and 1000 mg/day for eight weeks raised whole-blood NAD+ by 22%, 51%, and 142% respectively in healthy overweight adults, with no flushing and no significant adverse-event difference from placebo [4]. A multicenter, double-blind randomized trial of nicotinamide mononucleotide (NMN) at 300-900 mg/day for 60 days raised blood NAD+ at days 30 and 60 across every dose group versus placebo, and flagged 600 mg/day as the optimal dose [3].
That is the proven part. The unproven part is equally important: a 2025 Nature Metabolism review of the human evidence concluded that translation to hard clinical endpoints remains preliminary, that age-related NAD+ decline has been observed in only a limited number of human studies, and that tissue-level NAD+ data are sparse [14]. Raising a blood marker is not the same as changing an outcome. This site keeps those two facts on separate rows.
NAD+ versus its precursors — the distinction that matters
The most-searched confusion is also the most consequential one for anyone reading a label. NAD+ itself is large, charged, and poorly absorbed intact, so swallowing "NAD+" capsules is not how the molecule reaches your cells [14]. The studied oral approach is precursors: NMN and NR are converted to NAD+ inside the cell through the salvage pathway (the recycling route the body uses to rebuild NAD+, gated by the rate-limiting enzyme NAMPT) [5].
This is why the controlled evidence that matters is precursor evidence. When you read that a trial "raised NAD+," it almost always means oral NMN or NR raised whole-blood NAD+ — not that participants took NAD+ itself. The intravenous route is the exception, and it carries its own clearance and quality problems covered on the IV NAD+ and injectable routes page.
Is NAD+ a supplement or a drug? The regulatory picture
NAD+ and its precursors are sold in the United States as dietary supplements, not as approved drugs. There is no FDA-approved NAD+ medicine and no approved dose for any disease. Marketing language that implies otherwise is running ahead of the regulatory reality.
The NMN form sits inside an unsettled marketplace dispute: the FDA has taken the position that NMN is excluded from the dietary-supplement definition because it was authorized for investigation as a drug. That is a contested status question, not a finding that NMN is "banned" or "illegal" — it is a live disagreement about which regulatory bucket the ingredient belongs in. Anyone treating the category as settled in either direction is overstating it. The full safety and status breakdown lives on the NAD+ side effects and safety page.
What this ledger covers
Three routes, three very different evidence weights. Oral precursors carry the bulk of the controlled human data — single-dose and chronic dosing of NMN and NR has been generally well tolerated for weeks to months [4][6][7]. Intravenous NAD+ carries the weakest controlled evidence: infused NAD+ is rapidly cleared from plasma, and a compounded injectable was subject to an FDA Class I recall for endotoxin contamination — covered in full under IV NAD+ and injectable routes. Mechanism — sirtuins, PARPs, CD38 — is well characterized but largely worked out in cells and mice.
What follows is organized as a transparency ledger: every quantitative claim carries a study and a status tag, so you can see at a glance how strong each row really is. Start with the human clinical trials, check the doses used in the research, or read the frequently asked questions about NAD+.