NAD+ is the cell's central coenzyme, and the infused and injected research is thinner than the marketing.

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 you take. It is a coenzyme (a helper molecule an enzyme needs to do its job) that the body makes in every cell, and tissue levels drift down with age. Because the intact molecule is large and poorly absorbed by mouth, most oral "NAD+" products are actually precursors (building blocks the body converts into NAD+ — NMN and NR are the common ones). This site summarizes the published research on NAD+ and those precursors. It sells nothing and gives no dosing advice.

What the NAD+ literature has actually demonstrated

NAD+ is the cell's central electron carrier. It cycles between an oxidized form (NAD+) and a reduced form (NADH) to move electrons through glycolysis, the TCA cycle and mitochondrial respiration, which is how cells make ATP, their energy currency ^[5]. It is also a consumed substrate — a molecule that gets used up — by three families of signaling enzymes: sirtuins (cellular-maintenance enzymes that can't work without NAD+), PARPs (DNA-repair enzymes), and CD38 (an enzyme on cell surfaces) ^[5].

Tissue NAD+ falls with age. A 2016 mouse study identified CD38 as the principal NAD+-consuming enzyme whose activity rises with age; deleting CD38 preserved NAD+ and mitochondrial function in older animals ^[2]. In people, muscle biopsies from 119 older men across three populations linked sarcopenia (age-related muscle loss) to reduced NAD+ biosynthesis and mitochondrial capacity ^[10]. That age-related decline is the rationale behind raising NAD+ with precursors.

The most reproducible human result is narrow and real: oral precursors raise blood NAD+. Nicotinamide riboside at 100, 300 and 1000 mg/day for 8 weeks raised whole-blood NAD+ by 22%, 51% and 142% respectively in healthy overweight adults, with no flushing and no adverse-event difference from placebo ^[4]. This is a research digest of that evidence, organized by route — start with the human clinical trials, the doses used in the research, or the frequently asked questions.

NAD+ as a Dietary Supplement: Precursors vs Plain NAD+

Sold as a NAD supplement, "NAD+" is regulated as a dietary supplement, not an approved drug. The important distinction is what is actually in the capsule. Intact NAD+ is a 663-dalton charged dinucleotide that most cells do not take up whole and that survives the gut poorly, so plain oral NAD+ is widely considered an inefficient way to raise cellular NAD+ ^[5]. For that reason most oral products are precursors — the NMN and NR precursors the body absorbs and rebuilds into NAD+, or the older B3 vitamins niacin and nicotinamide — converted through the salvage and Preiss-Handler pathways ^[12].

The regulatory picture is genuinely unsettled for one precursor. The FDA has taken the position that NMN is excluded from the dietary-supplement definition because it was authorized for investigation as a drug — a marketplace dispute over status, not a finding that NMN is unsafe and not a ban ^[5]. Across precursors the better-supported claim is pharmacodynamic (blood NAD+ goes up), while hard clinical outcomes remain preliminary.

What NAD+ Research Has Measured (Not Claimed Benefits)

Searches for NAD+ benefits return a lot of promises. The honest version is what specific trials measured. In a multicenter, double-blind RCT, oral NMN at 300, 600 and 900 mg/day for 60 days dose-dependently raised blood NAD+ versus placebo (p≤0.001 at days 30 and 60) and improved six-minute walking distance, with 600 mg/day identified as the optimal dose and no safety signal at any level ^[3]. In prediabetic, postmenopausal women, 10 weeks of NMN at 250 mg/day significantly improved muscle insulin sensitivity, measured by clamp, with no change in body composition ^[1].

What the literature does not support is the leap from "blood NAD+ rose" to "aging reversed." A 2025 Nature Metabolism review of NAD+ precursor supplementation in human aging concluded that trials have shown limited efficacy for hard clinical endpoints and that tissue-level NAD+ data remain sparse ^[6]. The strongest anti-aging effects still come from rodents and may not transfer. This digest reports the measured outcome and flags the gap, rather than filling it.

The two routes this site reads closely: infusion and injection

The dealt lens here is the needle. NAD+ is also given parenterally — bypassing the gut — as an intravenous infusion or as an intramuscular or subcutaneous injection, and these preparations are compounded wellness products, not FDA-approved medicines. The controlled evidence for them is the thinnest in the whole field.

Infused NAD+ is cleared from plasma fast: a pilot pharmacokinetic study found near-complete plasma removal within roughly the first two hours of infusion ^[5]. Most clinical reports of intravenous use are pilot or retrospective rather than randomized, and a compounded injectable NAD+ product was subject to an FDA Class I recall for endotoxin contamination ^[5]. The detail lives on two pages: the NAD infusion research page covers IV pharmacokinetics and infusion-rate tolerability, and the injectable NAD+ studies page covers the parenteral route family. Both keep one rule: describe only what the cited studies measured.

What is NAD supplement used for?

NAD+ and its oral precursors (NMN, NR, niacin) are marketed as dietary supplements aimed at raising cellular NAD+, the coenzyme that declines with age. Controlled trials reliably show oral precursors raise blood NAD+ ^[4][3], while translation to clinical endpoints stays preliminary ^[6]. This site documents that research; it makes no claim that any product treats a condition.

Is NAD just vitamin B3?

Not exactly. NAD+ is the coenzyme the body builds from vitamin-B3-family precursors — niacin, nicotinamide and nicotinamide riboside — so the B3 vitamins are the raw materials, not NAD+ itself. The body converts them through the salvage and Preiss-Handler pathways ^[12]. Calling NAD+ "just B3" skips the several enzymatic steps in between.

What does NAD do for the body?

NAD+ is the cell's central electron carrier for making ATP and a consumed substrate for sirtuins, PARPs and CD38, the enzymes that govern DNA repair, gene regulation and inflammation ^[5]. Tissue NAD+ declines with age, partly because CD38 activity rises ^[2]. It is required machinery, present in every cell, not an optional add-on.

Is NAD a peptide?

No. NAD+ is a dinucleotide coenzyme — two nucleotides joined by phosphate bridges, about 663 daltons — not a peptide. It contains no amino acids and is synthesized in every cell from precursors rather than translated from a gene ^[5]. It belongs to a different chemical class entirely from the peptides it is sometimes shelved beside.

What does NAD stand for?

NAD stands for nicotinamide adenine dinucleotide. It exists in an oxidized form (NAD+) and a reduced form (NADH) that interconvert as the coenzyme shuttles electrons during metabolism ^[5]. The plus sign denotes the oxidized, electron-accepting form.

What does NAD mean in medical terms?

In biochemistry, NAD means nicotinamide adenine dinucleotide, a coenzyme central to redox metabolism and to NAD-consuming signaling enzymes ^[5]. Note the acronym is also used unrelatedly in clinical charting to mean "no abnormality detected," so context matters.