NAD+ is the cell's central coenzyme, charted here from its precursors through the safety evidence to the compounded edge.

The short version

NAD+ (a fuel-handling helper molecule every cell uses to turn food into usable energy) is a coenzyme — a small helper an enzyme needs to do its job. It is not a drug and not a single product; it is sold as a dietary supplement. One catch the rest of this site keeps coming back to: NAD+ itself is large and poorly absorbed by mouth, so most pills actually contain a precursor (a building block the body converts into NAD+ — NMN and NR are the common ones). Human trials show those precursors reliably raise NAD+ in the blood. Whether that translates into the benefits people hope for is, so far, much less settled.

What is NAD+?

NAD+ stands for nicotinamide adenine dinucleotide — a coenzyme present in every living cell and one of the most consequential small molecules in metabolism. It is a redox carrier: it shuttles electrons (redox is the chemistry that moves electrons to release energy) through glycolysis, the TCA cycle and the mitochondrial electron transport chain to drive the synthesis of ATP, the cell's energy currency ^[5]. Chemically it is a dinucleotide — nicotinamide mononucleotide joined to adenosine monophosphate — with the molecular formula C21H27N7O14P2 and a molecular weight of about 663 Da ^[5]. It exists in an oxidized form (NAD+) and a reduced form (NADH); older literature called it Coenzyme I or DPN.

NAD+ is more than an energy intermediate. It is also a consumed substrate — a raw material used up — by three families of signaling enzymes: sirtuins (a family of cellular-maintenance enzymes that cannot work without NAD+), PARPs (DNA-repair enzymes), and CD38 (an enzyme on cell surfaces that breaks NAD+ down) ^[5]. Because these enzymes spend NAD+ rather than merely borrowing it, the cell must continually resynthesize it. Tissue NAD+ declines with age, and a 2016 study identified rising CD38 activity as a principal driver of that fall ^[2]. That decline is the rationale behind the entire precursor-supplement category ^[1].

NAD+ as a Dietary Supplement: What the Label Usually Contains

Read the back of an oral NAD+ supplement and you will usually find a precursor, not NAD+ itself. The reason is straightforward chemistry: NAD+ is a large, charged dinucleotide that most cells do not take up intact, so swallowing NAD+ is an inefficient way to raise it ^[12]. The forms that work by mouth are the building blocks the body assembles into NAD+ — chiefly NMN (nicotinamide mononucleotide), NR (nicotinamide riboside), and the vitamin-B3 compounds niacin and nicotinamide.

These precursors have real human evidence behind their ability to raise blood NAD+. In a randomized trial in healthy overweight adults, NR at 100, 300 and 1000 mg/day raised whole-blood NAD+ by 22%, 51% and 142% respectively over eight weeks ^[4]. A 2023 multicenter trial of NMN at 300-900 mg/day produced significant blood-NAD+ increases at 30 and 60 days across every dose group ^[3]. The NMN and NR precursors are covered in depth on the research page. None of this makes NAD+ an approved medicine: it is a supplement, the evidence is for raising NAD+ rather than curing anything, and the regulatory status of one popular form (NMN) is itself contested — covered as NAD+ safety and side effects, not settled here. You can see doses used in NAD+ research laid out separately.

What NAD+ Research Has and Has Not Shown

Start with the cleanest result: raising blood NAD+ with an oral precursor is well demonstrated and reproducible. The harder question — whether that produces meaningful clinical benefits in humans — is where the literature turns honest and mixed.

A handful of trials have measured genuine functional gains. Ten weeks of oral NMN (250 mg/day) significantly improved muscle insulin sensitivity in prediabetic, postmenopausal women, with no change in body weight or HbA1c ^[1]. A 2023 multicenter NMN trial reported improved walking distance alongside the rise in blood NAD+ ^[3]. But a 2023 review of human NAD+-boosting trials found the pattern repeated across studies: NAD+ metabolites rose consistently, while most functional endpoints — insulin sensitivity, energy expenditure, exercise capacity, body composition — showed no significant improvement ^[7]. A 2025 Nature Metabolism review of precursor supplementation in ageing reached the same conclusion: human efficacy data remain limited, and tissue-level NAD+ dynamics in people are still sparsely mapped ^[13].

The takeaway is not dismissive — it is precise. NAD+ precursors do what their pharmacology predicts; the clinical translation is the open chapter. What the human trials found sets out the studies in detail.

What this map covers

This is an editorial research digest, organized like an atlas of the NAD+ literature. The what the human trials found page surveys the mechanism and the controlled trials. The doses used in NAD+ research page sets out, for context only, the doses studied in named populations — with no human dosing instruction. Two regions get their own pages because they carry the most uncertainty: NAD+ safety and side effects covers tolerability, the contested NMN supplement status, and the compounded-injectable recall; IV NAD therapy research covers the infusion route, which has the weakest controlled evidence of any. A full reference list anchors every quantitative claim, and the frequently asked questions about NAD+ answer the most common queries directly.

What is NAD supplement used for?

NAD+ supplements are marketed to raise the body's NAD+, a redox coenzyme that declines with age. Most oral products are precursors (NMN, NR, niacin/nicotinamide) because NAD+ itself is poorly absorbed; trials show these reliably raise blood NAD+ ^[4]. Benefits for hard clinical endpoints, however, remain preliminary ^[13].

Does NAD make you look younger?

No cited trial demonstrates that raising NAD+ reverses visible aging in humans. The anti-aging rationale comes largely from rodent and mechanistic work, such as CD38-driven NAD+ decline ^[2]. A 2025 Nature Metabolism review concluded that human anti-aging efficacy data remain limited ^[13]. This site describes findings, not cosmetic claims.

Is NAD just vitamin B3?

Not quite. NAD+ is built from vitamin-B3-family precursors — niacin (nicotinic acid), nicotinamide, and the NR and NMN forms — but NAD+ itself is a dinucleotide coenzyme, not a vitamin ^[5]. The precursors feed NAD+ through the salvage and Preiss-Handler pathways ^[11].

Is NAD a peptide?

No. NAD+ is not a peptide. It is a dinucleotide coenzyme (nicotinamide mononucleotide joined to adenosine monophosphate; formula C21H27N7O14P2, about 663 Da) made in every cell, rather than a chain of amino acids ^[5].

What does NAD do for the body?

NAD+ shuttles electrons through glycolysis, the TCA cycle and oxidative phosphorylation to make ATP, and serves as a consumed substrate for sirtuins, PARPs and CD38 — enzymes that govern DNA repair, gene regulation and inflammation ^[5]. Tissue NAD+ declines with age, partly as CD38 activity rises ^[2].

What does NAD stand for?

NAD stands for nicotinamide adenine dinucleotide. It exists in an oxidized form (NAD+) and a reduced form (NADH) ^[5]. Older literature also refers to it as Coenzyme I or DPN (diphosphopyridine nucleotide).

What does NAD mean in medical terms?

In biochemistry, NAD means nicotinamide adenine dinucleotide — a coenzyme central to energy metabolism and to NAD+-consuming signaling enzymes (sirtuins, PARPs, CD38) ^[5]. As a charting abbreviation 'NAD' can carry other meanings; here it refers strictly to the coenzyme.