What is NAD+? What it does, benefits and what the evidence shows

NAD+ (nicotinamide adenine dinucleotide) is a coenzyme every cell in your body makes and uses constantly, not a peptide — it has no amino acid chain at all. It's central to how cells produce energy and repair DNA, levels of it fall as people age, and that decline is why it's sold on the grey market as an injectable and why its precursors, nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN), are sold as oral supplements. The evidence for those precursors raising NAD+ levels in humans is solid; the evidence that doing so delivers the benefits marketed around it is a lot thinner, and it varies a lot by which specific claim you're asking about.

What NAD+ is and how it works

Structurally, NAD+ is a dinucleotide: two nucleotides joined by their phosphate groups, one built on nicotinamide (a form of vitamin B3), the other on adenine. That's fundamentally different from a peptide, which is a short chain of amino acids linked by peptide bonds. NAD+ and compounds like BPC-157 or MOTS-C aren't different categories of the same thing — they're different kinds of molecule doing different jobs.

What NAD+ does is close to foundational biochemistry. It's required for roughly 500 enzymatic reactions in the body, acting as a hydrogen carrier in redox reactions that generate cellular energy, and it's the substrate that two other enzyme families depend on: sirtuins (which regulate genes tied to metabolism, inflammation and stress resistance) and PARPs (which repair damaged DNA), according to a widely cited 2018 review in Cell Metabolism (Rajman, Chwalek & Sinclair, "Therapeutic potential of NAD-boosting molecules: the in vivo evidence"). NAD+ levels aren't fixed — they rise and fall with food intake, exercise and time of day — but they trend downward with age, which is the biological observation that launched the entire NAD+ supplement category.

Here's the detail that matters most for anyone shopping this market: that same review states that, with the exception of neurons, mammalian cells can't import intact NAD+ from outside the cell. They have to build it themselves, mainly by salvaging it from nicotinamide, or from precursor forms including NR and NMN. That's the whole reason NR and NMN exist as separate, heavily marketed products rather than everyone just taking NAD+ directly — an oral NAD+ pill has a hard time doing anything most cells can use before it's broken down anyway. Injectable and IV "NAD+" products bypass digestion, but even there, most of the human data that actually exists was collected on the precursors, not on NAD+ itself. That distinction shows up constantly in vendor marketing and gets glossed over just as constantly, so it's worth keeping in mind through the rest of this article: some of the good evidence below is about NAD+ precursors raising your levels, not about NAD+ delivered directly doing something.

What people use it for

What the research actually shows

Raising NAD+ levels: this part is well established

The one claim with the most consistent human backing is the most basic one: taking an NAD+ precursor measurably raises NAD+ in your blood. In an 8-week, randomized, double-blind, placebo-controlled trial of 140 overweight but otherwise healthy adults (35 per group), oral nicotinamide riboside raised whole-blood NAD+ dose-dependently — by 22%, 51% and 142% at the low, medium and highest dose studied, respectively — within two weeks, and kept it elevated for the rest of the study (Conze, Brenner & Kruger, 2019, Scientific Reports). That's a real, dose-dependent, repeatedly replicated effect. What it doesn't tell you is whether a higher number on a blood panel translates into feeling or functioning any better — that's where the evidence gets thinner fast.

Insulin sensitivity: one real trial, a narrow population

A 10-week, randomized, placebo-controlled trial gave NMN to postmenopausal women who were overweight or obese and had prediabetes. Insulin-stimulated glucose disposal, measured with a hyperinsulinemic-euglycemic clamp, and skeletal-muscle insulin signaling both increased in the NMN group but not the placebo group (Yoshino et al., 2021, Science). That's a genuine, well-designed human trial — not animal data, not an open-label pilot — which is why it earns a "human trials" tier above. But it's one trial, in one specific population (postmenopausal, prediabetic, overweight women), and it hasn't been shown to generalize to healthy adults, men, or younger people, which the researchers themselves note.

Exercise capacity: modest gains in a small trial

A 6-week, randomized, double-blind trial split 48 amateur runners into four groups — placebo, or one of three ascending doses of NMN — and measured cardiopulmonary fitness before and after training. Oxygen uptake and power at the first and second ventilatory thresholds improved more in the medium- and high-dose groups than in the placebo group, but the study found no difference in peak VO2max or peak power between groups (Liao et al., 2021, Journal of the International Society of Sports Nutrition). In plain terms: some submaximal fitness markers moved, the headline "how fast can you go all-out" number didn't, in a 6-week study of 48 people.

Cognitive function: a placebo-controlled trial found nothing

This is the claim most worth being direct about. A 24-week, single-center, double-blind, placebo-controlled trial randomized 58 people with long-COVID 2:1 to nicotinamide riboside for 20 weeks or to placebo for 10 weeks followed by nicotinamide riboside, and tracked cognition on three separate validated tests, plus fatigue, anxiety, depression and sleep quality. NAD+ levels rose 2- to 3-fold in the treatment group, confirming the drug did what it was supposed to do biologically — but there was no significant difference between the NR and placebo groups on any cognitive, fatigue, mood or sleep measure (Wu et al., 2025, eClinicalMedicine). This is exactly the kind of trial "cognitive benefits" marketing rarely mentions: randomized, double-blind, placebo-controlled, and negative on its primary cognitive outcomes, though small at 58 participants and partly funded by the maker of nicotinamide riboside. The authors call for larger trials.

Addiction and withdrawal: real interest, thin proof

IV NAD+ clinics market heavily to people trying to get through withdrawal, and there's a real scientific rationale behind it — NAD+ metabolism intersects with brain pathways involved in addiction. But a 2020 review in Antioxidants that surveyed this literature states plainly that "clinical studies showing the use of NAD+ for the treatment of addiction are limited," and the clinical benefit it cites for IV NAD+ in alcohol and opioid withdrawal traces back to a preliminary report published in 1961, not a modern placebo-controlled trial (Braidy, Villalva & van Eeden, 2020, Antioxidants).

Anti-aging and longevity: real mouse data, no human data

The mouse evidence here is genuinely strong. In a 12-month study — essentially the mouse equivalent of a lifelong intervention — daily NMN suppressed age-related weight gain, improved insulin sensitivity and plasma lipids, and preserved eye function and physical activity in aging C57BL/6N mice, without obvious toxicity (Mills et al., 2016, Cell Metabolism). None of that has an equivalent human trial, and it's worth saying explicitly: this is a rodent-lifespan study, and nothing about it has been demonstrated in people. Treat "extends healthy lifespan" as a claim about mice until a comparable human study exists.

Side effects and risks

Oral NR and NMN have a reassuring safety record in the trials that exist. The NIAGEN (NR) trial above reported no significant differences in adverse events between NR and placebo groups, even at the highest dose studied, with no flushing and no adverse effect on LDL cholesterol (Conze, Brenner & Kruger, 2019). The long-COVID trial used a high daily dose of NR for up to 20 weeks without new safety signals, though it did see meaningfully higher dropout in the NR arm than placebo (Wu et al., 2025).

IV NAD+ is a different story, and this is where the grey market mostly operates. A 2026 retrospective chart review compared commercially administered IV NAD+ (six clients) against IV NR (eight clients) in a commercial setting. Clients receiving IV NAD+ reported moderate-to-severe gastrointestinal symptoms, increased heart rate, and chest pressure during the infusion; the NR group had only minor tingling and mild cramping. Symptoms resolved once the infusion ended, but the NAD+ group's infusions took nearly three times as long on average (97 minutes versus 37) because of how often the rate had to be slowed to manage symptoms (Reyna et al., 2026, Frontiers in Aging). That's a retrospective chart review of just 14 clients, not a randomized trial — early human data, not definitive — but it's the most direct comparison available, and it says IV NAD+ itself is harder on the body during infusion than its precursor.

No NAD+, NR or NMN product is FDA-approved as a drug for any of the uses discussed above. NMN's regulatory status as a dietary ingredient was itself contested: the FDA told suppliers in 2022 that NMN was excluded from the dietary supplement definition because of its prior investigation as a drug, then reversed that position in September 2025 after a citizen petition and litigation, and sent letters in December 2025 confirming NMN can be lawfully marketed as a supplement (NutraIngredients, December 9, 2025). None of that history says anything about injectable "NAD+" sold research-use-only, which sits entirely outside the supplement framework and has no equivalent safety review.

On the grey-market-specific risks: our data on NAD+ vials is the thinnest of any compound we track, and that thinness is itself a finding. Purity was reported on 3 of 28 tested vials — most buyers ordering NAD+ tests are checking dose, not purity — with a median of 99.80% among the few that were measured, and 0 of the 3 came back under 95%. Endotoxin testing turned up something worth flagging directly: among 16 NAD+ endotoxin results in our data as of September 29, 2026, 11 vials from a single vendor were tested the same day, and 8 of those 11 came back above 500 EU per vial — a same-day cluster, not a scattered pattern, in a product that's often injected. For research use only, this is exactly the kind of thing independent testing exists to catch, and exactly the kind of thing you won't see on a vendor's own marketing page.

What the lab tests show

As of September 30, 2026, our database includes 28 NAD+ vials from 11 vendors, drawn from 15 lab reports dated November 2024 through August 2026 — a small sample by our standards, and one where a single vendor's results can move the numbers more than in a heavily tested compound like tirzepatide. Dose against label ran a median of +7.3% across the 27 vials with a measured amount: 7 landed within ±5% of label (15 were within ±10% as of September 29, 2026), 2 measured more than 20% under label and 6 more than 20% over, with 2 of those more than 50% over. 5 of the 28 tested vials (18%) failed outright under our definition (empty, under 95% purity, more than 20% under label, or more than 50% over) — as of September 29, 2026, a higher failure rate than most compounds we track, on a much smaller sample.

Here's how the ranked vendors for NAD+ look right now, based on lab reports buyers have actually submitted — this updates as new reports come in, and it may be short or empty if too few vendors have five or more reports on file yet:

Ranked isn't automatically good, and a short table here reflects genuinely thin data on this specific compound, not necessarily a hidden problem with the market. For a live, continuously updated version of these numbers, see the NAD+ results page.

Buying smarter

If you're buying NAD+, check the vendor's specific record on the NAD+ results page rather than a vendor's general reputation — a vendor with a strong tirzepatide record has told you nothing about how carefully they source or store NAD+, which is chemically unstable and can degrade differently in storage than a peptide would. Given how thin the purity data is on this compound specifically, a purity test is arguably more useful here than on a heavily tested compound where purity is already well established. How to get a peptide tested walks through ordering independent purity, identity and quantity testing, and when an endotoxin add-on is worth the cost — which, given the cluster of high endotoxin results above, is a genuinely relevant question for this specific compound. If a report comes back with a purity fail, a large underfill, or a high endotoxin result, the standard next step applies here too: stop using that batch, tell anyone else who bought from the same run, bring the report to the vendor, and submit it to VendorVerify so the next buyer checking that vendor's NAD+ results sees it.

Database figures without a date update automatically from VendorVerify's lab results; dated figures are snapshots. Research-labeled NAD+, NR and NMN products sold on the grey market are for research use only and are not reviewed by the FDA for the uses discussed above. This isn't medical advice.