# NAD+ — The Precursor Record: NMN and NR Trials, Filed and Cited > NAD+ is the cell's central redox coenzyme. This digest files the human NMN and NR trials that raised blood NAD+ — what they measured, route by route — and keeps the coenzyme distinct from its precursors. Cited. A night-edition reading of the research record: the human NMN and NR studies that raised blood NAD+, what they measured, and where oral "NAD+" capsules and the IV drip part company from the evidence. ## The short 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), and the body makes it from precursors (building blocks the body converts into NAD+ — NMN and NR are the common ones). Tissue NAD+ falls as we age. Plain NAD+ swallowed as a pill is poorly absorbed; the trials that actually raised blood NAD+ in people used the precursors. This page files what those studies measured, and keeps the coenzyme separate from the building blocks. ## What the NAD+ record actually shows NAD+ sits at the center of cellular energy. It carries electrons through glycolysis, the citric-acid cycle, and the mitochondrial electron-transport chain to make ATP, and it doubles as a consumed fuel for signaling enzymes — the sirtuins, the PARPs, and CD38 — that govern DNA repair, gene regulation, and inflammation [5]. Tissue levels of this coenzyme decline with age, and that decline is the entire rationale behind the supplement category [5]. Here is the distinction this digest holds firm, because most coverage blurs it: NAD+ the molecule is large and charged (molecular weight roughly 663 Da), and it is poorly taken up intact when swallowed. The compounds people actually take are precursors — nicotinamide mononucleotide (NMN), nicotinamide riboside (NR), and the older vitamin-B3 forms niacin and nicotinamide — which the body converts into NAD+ through the salvage and Preiss-Handler pathways [9]. When a study reports that participants "took NAD+," check the methods: almost always they took a precursor. We never conflate the two. The human evidence for raising blood NAD+ is genuinely strong. In a multicenter, double-blind, placebo-controlled trial, oral NMN at 300, 600, and 900 mg/day for 60 days raised blood NAD+ dose-dependently in middle-aged adults, with the increase significant at days 30 and 60 across every NMN group (p≤0.001) [3]. Oral NR ran a cleaner dose-response still: 100, 300, and 1000 mg/day for eight weeks lifted whole-blood NAD+ by 22%, 51%, and 142% respectively, with no flushing and no significant adverse-event difference from placebo [4]. Those are the headline figures, and they replicate. Browse the [human clinical trials](/research) for the full register, or the [NMN vs NR comparison](/nmn-vs-nr) for the precursor-by-precursor read. ## NAD+ as a dietary supplement: what the label means An NAD supplement is a dietary supplement, not an approved medicine — NAD+ and its precursors are not FDA-approved to treat, prevent, or cure any disease [8]. What the bottle delivers is, in nearly every case, a precursor that the body builds into NAD+, not the coenzyme itself in a usable oral form. That is the most important thing the label does not tell you, and it is why a reader chasing results should read "NAD supplement" as "NAD precursor supplement." Two regulatory wrinkles belong in plain view. First, the supplement status of NMN is contested: the FDA has taken the position that NMN is excluded from the dietary-supplement definition because it was authorized for investigation as a drug, which has created marketplace uncertainty rather than a settled ban [8]. Second, injectable and IV NAD+ — sold in wellness settings — is a compounded preparation, not an approved product, and a compounded NAD+ injection has been subject to an FDA Class I recall over elevated bacterial endotoxin [8]. Both points are filed under the caution desk on the [research page](/research), not buried. ## How this digest is organized We file by department, the way a newspaper files by desk. NMN — the highest-volume precursor — gets its own page, drawing on the [NMN research](/nmn) and the human trials that used it. NR, the most clinically studied precursor, runs head-to-head with NMN on the [NMN vs NR comparison](/nmn-vs-nr) page. The [doses studied in the literature](/dosage) are catalogued as study parameters, never as instructions. And the [common questions about NAD+](/faq) collect the definitional and safety questions readers actually ask. Every quantitative claim on this site carries a citation to a named study, and the [full reference list](/references) resolves each one to its PubMed record. This is editorial work — a reading of the published science. It is not medical advice, and nothing here is for sale. ## What is NAD supplement used for? NAD+ is an endogenous redox coenzyme; supplements — mostly the precursors NMN, NR, or niacin — are studied for raising the blood NAD+ levels that decline with age [5][9]. In trials, those precursors reliably increase blood NAD+, but this is research framing: NAD+ is not an approved treatment for any condition, and no dosing instruction is given here. ## Is NAD just vitamin B3? No. NAD+ is the coenzyme itself; vitamin B3 forms — niacin, nicotinamide, and the precursors NR and NMN — are the building blocks the body converts into NAD+ via the salvage and Preiss-Handler pathways [9]. The vitamins are upstream of the coenzyme, not the same molecule, which is exactly the distinction this digest keeps firm. ## What does NAD do for the body? NAD+ carries electrons through energy metabolism — glycolysis, the citric-acid cycle, and oxidative phosphorylation — to make ATP, and it is a consumed substrate for the sirtuins, PARPs, and CD38, the enzymes governing DNA repair, gene regulation, and inflammation [5]. It is the cell's central redox currency and a signaling fuel at once. ## Is NAD a peptide? No. NAD+ is a dinucleotide coenzyme — nicotinamide joined to adenine through two bridging phosphates — not a peptide and not a protein. It is a small endogenous metabolite of roughly 663 Da, with the molecular formula C21H27N7O14P2 [5]. The "prescribed" in this site's name is editorial framing for a research desk, not a claim that NAD+ is a peptide or a drug. ## What does NAD stand for? NAD stands for nicotinamide adenine dinucleotide. The plus sign in NAD+ denotes the oxidized form, which is reduced to NADH when the cell breaks down fuel; NADH then hands its electrons to the electron-transport chain to drive ATP synthesis [5]. The pair cycles continuously — the redox couple at the heart of metabolism. ## What does NAD mean in medical terms? In biochemistry, NAD refers to nicotinamide adenine dinucleotide, the central redox coenzyme historically called Coenzyme I [5]. It is an endogenous metabolite present in every living cell — not a prescription drug, not a single marketed medicine, and not on any approved-indication label. This site reads the research record on it, nothing more. --- A night-edition broadsheet on the NAD+ record — the coenzyme filed apart from the NMN and NR precursors that rebuild it, the human trials that raised blood NAD+ kept on their own desk from the poorly-absorbed oral pill and the rapidly-cleared IV drip, and the contested NMN status posted as filed; no clinic behind this masthead and nothing here prescribed, compounded, or sold.