NAD+ research: what does the evidence actually show?

Research-use notice: this article is for legitimate laboratory and educational research only. It does not provide guidance for human use, administration, dosing or treatment.

NAD+ is not a peptide. It is a coenzyme, nicotinamide adenine dinucleotide, found in every living cell, and it is now one of the most heavily marketed molecules in the wellness trade. The research base behind it is large, but most of it concerns NAD+ biology inside cells and the oral precursors NMN and NR, not NAD+ itself supplied from outside. This article sets out what NAD+ is, how it differs from NMN and NR, what cell, animal and human studies have measured, why the “NAD+ declines with age” claim is less settled than it sounds, and what to check on a batch report.

What is NAD+?

Nicotinamide adenine dinucleotide is two nucleotides joined through their phosphate groups: one carries adenine, the other nicotinamide. It exists in an oxidised form (NAD+) and a reduced form (NADH), and the cell cycles continuously between the two to move electrons in glycolysis, the citric acid cycle and the mitochondrial respiratory chain. That redox role is textbook biochemistry and is not in dispute.

A second role attracted the recent attention. NAD+ is also a substrate that enzymes consume: sirtuins (SIRT1–7), poly(ADP-ribose) polymerases (PARPs) and the ecto-enzyme CD38 all split NAD+ and release nicotinamide. Because those enzymes are involved in DNA repair, gene regulation and inflammation, the level of NAD+ available to them became a research question in its own right.

NAD+ vs NMN vs NR: what is the difference?

The three are often discussed as if interchangeable. They are not. NMN (nicotinamide mononucleotide) and NR (nicotinamide riboside) are precursors: molecules the cell converts into NAD+ through the salvage pathway shown above. NAD+ is the finished coenzyme.

The last two rows matter for interpreting the literature. Almost every “NAD+ supplementation” study in people used NR or NMN by mouth, measured NAD+ in blood cells, and inferred something about tissues. Very few measured what happens when NAD+ itself is supplied. The two bodies of evidence should not be merged.

Does NAD+ really decline with age?

This is the premise behind most NAD+ interest, and it is weaker than its repetition suggests. A 2021 review by Peluso and colleagues in Nutrients, titled “Age-Dependent Decline of NAD+: Universal Truth or Confounded Consensus?”, went through the human data and found it thin:

• Skin: a 2012 study of 49 pelvic skin samples taken during unrelated surgery found NAD+ roughly two-thirds lower in young adults than in newborns, and lower again by middle age, but it was cross-sectional and the groups were small.
• Brain: two magnetic resonance spectroscopy studies, of 17 and 16 people, estimated declines of roughly 10–20% between young adulthood and the seventh decade.
• Blood: one study of 30 people reported NAD+ about 15–20% lower in whole blood and plasma in older adults; another, of 19 people, reported plasma NAD+ 80–90% lower. Two results that far apart point to a measurement problem.

Every one of those human studies was cross-sectional, so none followed NAD+ in the same people over time, and the review noted that how levels behave in the nucleus, cytoplasm and mitochondria during human ageing has been largely ignored. The 2021 Nature Reviews Molecular Cell Biology review by Covarrubias and colleagues describes a gradual age-related decline in tissue NAD+ across model organisms including rodents and humans, but the mechanistic work behind it (CD38 upregulation, NAMPT dampened in inflammatory settings) comes mainly from mouse studies.

What the precursor trials show

Because this is where the human data are, it is worth being precise about them even though the compounds are NMN and NR rather than NAD+.

A 2023 update in Advances in Nutrition by Song and colleagues reviewed ten published human NMN trials and listed a further 24 completed-but-unpublished (13) or ongoing (11). Doses ranged widely, durations ran from a single dose to about three months, and eight of the ten trials had between 8 and 66 participants, mostly aged 55 and over. Where blood NAD+ was measured it rose by 1.7- to 2.57-fold. Some trials reported changes in measures such as walking endurance or muscle insulin sensitivity; others found no change in sleep quality or fatigue. One of the more careful studies found that blood-cell NAD+ rose while skeletal-muscle NAD+ did not. The authors’ summary was that clear evidence of anti-ageing effects in people “is still scarce”, and that the work is primarily at the phase 1 level.

The NR literature is similar in shape: oral NR raises blood NAD+ metabolites, and trials measuring downstream clinical outcomes have mostly been small and mixed. Neither NMN nor NR has a UK marketing authorisation as a medicine. In the EU, NMN is regulated as a novel food: the European Food Safety Authority published a positive safety opinion on one applicant’s NMN in May 2026, but it had not been added to the Union list at that point, and the UK runs its own novel-food authorisation process through the Food Standards Agency. In the United States the FDA stated in late 2022 that NMN was excluded from the dietary-supplement definition; the trade body NPA sued in August 2024, and in September 2025 the FDA reversed its position.

The human evidence for NAD+ itself

Here the record is short. The main study is a 2019 pilot by Grant and colleagues in Frontiers in Aging Neuroscience. Eleven healthy men aged 30–55 took part; eight received 750 mg of NAD+ by six-hour intravenous infusion and three received saline. Blood and urine were sampled through the infusion and after it.

The finding that matters for anyone interpreting NAD+ is what happened in the first two hours: nothing measurable. Plasma NAD+ and its metabolites did not change until after the two-hour mark. By six hours plasma NAD+ had risen by 398% over baseline, with nicotinamide (409%), methylnicotinamide (350%) and ADP-ribose (393%) up by similar amounts. The authors concluded that infused NAD+ was being rapidly and completely removed from plasma for at least the first two hours, consistent with uptake and breakdown by tissues, not with intact NAD+ circulating freely. No adverse events were recorded during the infusions, but the study measured pharmacokinetics only; it was not designed to assess safety or any clinical outcome. That is, as of October 2026, the extent of the controlled human data on supplied NAD+.

The surrounding commercial activity is much larger than the evidence. NAD+ drips are widely sold by private clinics. In the UK the Advertising Standards Authority has ruled against unsupported health claims for intravenous “drip” products on several occasions, and in April 2020 CAP, working with the MHRA, put IV drip advertisers on notice over claims that drips could prevent or treat COVID-19. None of that is evidence either way about NAD+; it is a reminder that claims and data have come apart.

Cell and animal research

Inside the laboratory the picture is richer and better controlled, which is exactly why NAD+ is a useful research material.

Cell culture

NAD+ is a standard reagent in enzyme assays: dehydrogenase kinetics, sirtuin and PARP activity, and NAD+/NADH ratio measurements. It is also the substrate in studies of CD38, the membrane enzyme that degrades extracellular NAD+ and whose expression rises with age and inflammation in mouse tissue. Billington and colleagues showed in 2008 that two mammalian cell types in culture could take up NAD+ at low concentrations, which qualified the earlier assumption that it never crosses membranes; in a living system, though, extracellular NAD+ is also being degraded by CD38 and related enzymes, so uptake and breakdown compete.

Animal models

Most in vivo work used NMN or NR in mice and rats and reported changes in mitochondrial function, glucose handling and muscle performance in aged animals. Direct NAD+ administration in rodents is less studied, partly because of the uptake and stability questions above. The 2021 Covarrubias review is the most complete map of this literature.

What this means for a research design

• Be precise about the molecule. A result obtained with NR or NMN is not a result for NAD+, and the reverse. Report which one was used, and in what form (free acid, sodium salt, chloride).
• Measure NAD+ directly. Enzymatic cycling assays and LC-MS both work; LC-MS can separate NAD+ from NADH and from the precursors and breakdown products. A plasma value alone says little about tissue.
• Control for extracellular degradation. In cell work, CD38 and nucleotide pyrophosphatases break NAD+ down in the medium. Measure what remains, not what was added.
• Prepare fresh and keep it cold and slightly acidic. NAD+ is stable in mildly acidic solution and degrades in alkaline conditions and with heat, losing nicotinamide and leaving ADP-ribose. NADH is the opposite: destroyed by acid, stable in alkali, a difference Lowry and colleagues documented in 1961 and which enzymatic assays still exploit. Our reconstitution method article covers solvent choice, pH and aliquoting.

How to check an NAD+ batch

NAD+ is a small, well-characterised molecule, so a batch report should be more definitive than a peptide report. Check:

• The batch number matches the vial label.
• Identity by mass spectrometry or by HPLC retention against a reference standard, with the observed mass consistent with 663.4 Da for the free acid.
• Purity as an HPLC area percentage, and ideally a note of the main impurity, which for NAD+ is usually nicotinamide or ADP-ribose from hydrolysis.
• Water content and salt form if stated, since both affect the mass of actual NAD+ in the vial.
• Method, date and report reference so the result can be verified with the laboratory.

Thistle publishes the laboratory report for the current NAD+ batch on the product page, and any batch can be checked on our batch report lookup. For the general method, see How to read a peptide COA and What does 99% purity actually mean?

Thistle supplies NAD+ — 500mg Research Material at £47.99, and the DSIP + Epitalon + NAD+ — Research Set at £76.99, each with a batch laboratory report.

Is NAD+ legal in the UK?

NAD+ has no UK marketing authorisation as a medicine and is not a controlled drug under the Misuse of Drugs Act 1971. As a naturally occurring coenzyme it is widely sold as a laboratory reagent. Presentation decides how it is regulated: in April 2026 the MHRA said that where clinics make medicinal claims for peptide injections, those products will be treated as medicines under the Human Medicines Regulations 2012. The same test, what is claimed for a product, applies to NAD+, and the ASA has ruled against unsupported health claims for intravenous drips on several occasions since 2020. Thistle supplies NAD+ as a research material and makes no claims about treating, preventing or improving any condition.

NAD+ is not named anywhere on the World Anti-Doping Agency’s 2026 Prohibited List, nor are nicotinamide, NMN or NR. The list’s S0 category is a catch-all for pharmacological substances with no regulatory approval for human therapeutic use, so “not named” is not the same as a ruling that a substance is permitted.

This section is general information, not legal advice.

Storage and handling

NAD+ is supplied as a lyophilised powder in a sealed vial. It is hygroscopic and sensitive to heat, light and alkaline conditions. Keep the vial sealed, dry and cold, bring it to room temperature before opening to avoid condensation, and prepare solutions fresh. See our storage guide.

NAD+ FAQs

Is NAD+ a peptide?

No. It is a dinucleotide coenzyme built from two nucleotides, not from amino acids. It appears in peptide catalogues because the same laboratories use it, not because it is chemically related.

Is NMN the same as NAD+?

No. NMN is a precursor one enzymatic step before NAD+. Almost all the published human trials used NMN or NR by mouth and measured NAD+ in blood; they are not trials of NAD+ itself.

Has NAD+ been proven to slow ageing?

No. The age-related decline in human tissue is itself less well documented than usually stated, the precursor trials are small and mixed, and the only controlled human study of supplied NAD+ was a pharmacokinetic pilot in eleven men that measured no clinical outcomes.

Why does NAD+ need to be kept cold and acidic?

The glycosidic bond between nicotinamide and the ribose is labile in alkaline conditions and at raised temperature, releasing nicotinamide and ADP-ribose. Mildly acidic, cold storage slows this. Solutions should be prepared fresh.

How much does NAD+ cost in the UK?

Prices vary by supplier and by amount. At the time of writing, Thistle sells NAD+ 500mg at £47.99. Price says nothing about content or purity, so check the batch report whichever supplier you use.

Sources

• Covarrubias AJ, Perrone R, Grozio A, Verdin E. NAD+ metabolism and its roles in cellular processes during ageing. Nature Reviews Molecular Cell Biology. 2021;22(2):119–141. Review.
• Peluso A, Damgaard MV, Mori MAS, Treebak JT. Age-Dependent Decline of NAD+: Universal Truth or Confounded Consensus? Nutrients. 2021;14(1):101. Review of the human evidence.
• Grant R, Berg J, Mestayer R, et al. A Pilot Study Investigating Changes in the Human Plasma and Urine NAD+ Metabolome During a 6 Hour Intravenous Infusion of NAD+. Frontiers in Aging Neuroscience. 2019;11:257. 11 men, 8 NAD+ and 3 saline; pharmacokinetics only.
• Song Q, Zhou X, Xu K, et al. The Safety and Antiaging Effects of Nicotinamide Mononucleotide in Human Clinical Trials: an Update. Advances in Nutrition. 2023;14(6):1416–1435. Ten published NMN trials reviewed.
• Massudi H, Grant R, Braidy N, et al. Age-Associated Changes In Oxidative Stress and NAD+ Metabolism In Human Tissue. PLoS ONE. 2012;7(7):e42357. The pelvic-skin study.
• Billington RA, Travelli C, Ercolano E, et al. Characterization of NAD uptake in mammalian cells. Journal of Biological Chemistry. 2008;283(10):6367–6374. Cell culture.
• Grozio A, Mills KF, Yoshino J, et al. Slc12a8 is a nicotinamide mononucleotide transporter. Nature Metabolism. 2019;1(1):47–57. And Schmidt MS, Brenner C. Absence of evidence that Slc12a8 encodes a nicotinamide mononucleotide transporter. Nature Metabolism. 2019;1(7):660–661. The NMN transporter dispute.
• Lowry OH, Passonneau JV, Rock MK. The Stability of Pyridine Nucleotides. Journal of Biological Chemistry. 1961;236:2756–2759. Oxidised forms destroyed by alkali, reduced forms by acid.
• Hogan KA, Chini CCS, Chini EN. The Multi-faceted Ecto-enzyme CD38: Roles in Immunomodulation, Cancer, Aging, and Metabolic Diseases. Frontiers in Immunology. 2019;10:1187. Extracellular NAD+ degradation.
• Zarei A, Khazdooz L, Madarshahian S, et al. Synthesis, Stability, and Bioavailability of Nicotinamide Riboside Trioleate Chloride. Nutrients. 2022;14(1):113. NR hydrolysis in water.
• EFSA Panel on Nutrition, Novel Foods and Food Allergens. Safety of beta-nicotinamide mononucleotide (β-NMN) pursuant to Regulation (EU) 2015/2283. EFSA Journal. 2026;24(5):e10007. Positive safety opinion, 11 May 2026; Commission authorisation is a separate step (NutraIngredients report, 13 May 2026). US Food and Drug Administration: FDA letters: β-NMN is excluded from the dietary supplement definition (October and November 2022, as reported by the National Law Review); NPA lawsuit, August 2024; and FDA reversal, September 2025 (Nutritional Outlook).
• Committee of Advertising Practice / Advertising Standards Authority. Putting IV drip advertisers on notice. 27 April 2020, with the MHRA; and Advice online: intravenous nutritional therapy, updated 6 February 2024.
• World Anti-Doping Agency. Prohibited List 2026. NAD+ not named; S0 non-approved substances is a catch-all category.
• Aesthetics Journal. MHRA investigates clinics following peptide claims. 15 April 2026.

Published by Thistle BioLabs, a UK supplier of research materials. This article summarises external research, not studies conducted by Thistle. Educational information only; no medical advice or recommendation for personal use.