NAD+ is the cell's central redox coenzyme, read here through the oral, injectable, and IV literature.

The short version

NAD+ (a fuel-handling helper molecule every cell uses to turn food into energy) is not a drug and is not one product on a shelf. It is a coenzyme — a helper molecule an enzyme needs to do its job — that your body makes and that drops in your tissues as you 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 large and poorly absorbed when swallowed. This page reads what the studies measured, route by route, and cites each number.

What NAD+ is, in one console readout

NAD+ stands for nicotinamide adenine dinucleotide. It is the cell's central redox carrier — "redox" being the electron-shuttling chemistry that releases energy — cycling between an oxidized form (NAD+) and a reduced form (NADH) as it moves electrons through glycolysis, the TCA cycle, and the mitochondrial electron transport chain to make ATP ^[5]. It is also a consumed substrate: the enzymes sirtuins (a family of cellular-maintenance enzymes that cannot work without NAD+), PARPs (DNA-repair enzymes), and CD38 all spend NAD+ as they run ^[5].

The molecule is a dinucleotide, not a peptide: a nicotinamide ring joined to an adenine nucleotide through two bridging phosphates, molecular formula C21H27N7O14P2, molecular weight 663.43 Da, CAS 53-84-9. Tissue NAD+ falls with age, and one driver is the NAD+-consuming ectoenzyme CD38, which rises with age and inflammation ^[2][5]. That decline is the entire rationale behind the supplement market — and behind this digest reading what the NAD+ and precursor studies actually found. If you want the one-paragraph version of what NAD+ is before going deeper, the short version sits at the top of this page; the common NAD+ questions cover the rest.

NAD+ as a Supplement: Why Most Products Are Precursors

An NAD supplement is, in practice, almost never NAD+ itself. NAD+ is a large, charged molecule that cells do not freely take up intact, so swallowing NAD+ is widely considered an inefficient way to raise it. The rational oral approach is a precursor the body converts to NAD+ inside the cell — chiefly NMN (nicotinamide mononucleotide) and NR (nicotinamide riboside), both vitamin-B3-family molecules, plus plain niacin and nicotinamide. These are sold as dietary supplements, not approved drugs.

The precursor data is the strong part of the human record. In a randomized trial, NR at 100, 300, and 1000 mg/day for 8 weeks raised whole-blood NAD+ by 22%, 51%, and 142% respectively, with no significant adverse-event difference from placebo at any dose ^[4]. NMN at 300, 600, and 900 mg/day for 60 days likewise raised blood NAD+ at days 30 and 60 across all groups versus placebo (p ≤ 0.001) in a multicenter double-blind trial ^[3]. The two leading oral options are compared as NMN vs NR precursors on the research page. The honest caveat: raising blood NAD+ is well demonstrated; translating that to hard clinical outcomes in humans remains preliminary, a point a 2025 Nature Metabolism review made directly ^[14].

One marketplace note belongs here. The regulatory 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. That is a marketplace dispute over a category, not a finding that NMN is banned or unsafe ^[14]. None of NAD+, NMN, NR, or nicotinamide is prohibited by WADA.

Two routes the search demand conflates: oral, IV, and injectable

Search interest treats "NAD+," "NAD injection," and "NAD IV therapy" as one thing. The studies do not. The route changes the evidence and the pharmacokinetics, so this digest keeps them on separate channels.

Oral precursors carry the bulk of the controlled human data: capsules or powder of NMN, NR, or nicotinamide, absorbed over days, raising whole-blood NAD+ that stays elevated through 8-to-12-week dosing ^[3][4]. IV NAD+ is a compounded, unapproved wellness therapy with the weakest controlled evidence; a pharmacokinetic pilot infusing 750 mg over 6 hours found plasma NAD+ undetectable for roughly the first 2 hours, with extensive extracellular metabolism — infused NAD+ is rapidly cleared ^[6]. Injectable NAD+ (subcutaneous or intramuscular, compounded) has minimal peer-reviewed pharmacokinetic data. The injectable lens is covered in depth on NAD injection research and NAD IV therapy.

What does NAD do for the body?

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

Is NAD a peptide?

No. NAD+ is not a peptide. It is a dinucleotide coenzyme — a nicotinamide ring plus an adenine nucleotide joined by phosphate groups, molecular formula C21H27N7O14P2, molecular weight 663.43 Da. Peptides are short chains of amino acids; NAD+ shares none of that structure.

What does NAD stand for?

NAD stands for nicotinamide adenine dinucleotide. Its oxidized form is written NAD+ and its reduced form NADH; the two interconvert as the coenzyme shuttles electrons during metabolism ^[5]. It was historically also called Coenzyme I or DPN (diphosphopyridine nucleotide).

What does NAD mean in medical terms?

In biochemistry, NAD means nicotinamide adenine dinucleotide, a coenzyme essential for hundreds of oxidoreductase reactions and for sirtuin, PARP, and CD38 signaling ^[5]. It is endogenous — synthesized in every cell from tryptophan, nicotinic acid, and the salvage pathway — not a prescribed medicine.

Is NAD just vitamin B3?

NAD+ is not vitamin B3 itself, but it is built from B3-family precursors — niacin, nicotinamide, and nicotinamide riboside. NAD+ is the dinucleotide coenzyme those vitamins are converted into inside cells through the salvage and Preiss-Handler pathways ^[5]. The vitamins are the input; NAD+ is the product.

Is taking NAD orally effective?

Oral NAD+ itself is poorly taken up by cells intact, so most experts consider oral precursors (NMN, NR) the rational approach. Precursor trials reliably raise blood NAD+ — NR by up to 142% at 1000 mg/day ^[4] — while plain oral "NAD+" capsules are widely considered largely ineffective for raising the coenzyme.

What is NAD supplement used for?

NAD supplements — mostly precursors like NMN and NR sold as dietary supplements — are marketed and studied for raising the blood NAD+ that declines with age ^[3][4]. Research has measured effects on muscle insulin sensitivity and physical performance ^[1][3], but human efficacy for hard clinical endpoints remains preliminary ^[14]. This is description of studies, not a use recommendation.