NAD+

What NAD+ is

Nicotinamide adenine dinucleotide is a small molecule found in every living cell: two nucleotides, one built on nicotinamide and one on adenine, joined through their phosphates by a pyrophosphate bridge. The oxidised form, written NAD+ for the positive charge on the pyridinium nitrogen of the nicotinamide ring, accepts a hydride ion to become the reduced form, NADH, and the interconversion of the two is how hundreds of dehydrogenases move electrons through glycolysis, the citric acid cycle, fatty-acid oxidation and the respiratory chain [1, 2]. The older literature calls it coenzyme I or DPN (diphosphopyridine nucleotide).

NAD+ is not a peptide, and a reader coming to it from the rest of this catalogue should set aside the assumptions that go with peptides. It has no sequence, no counter-ion from synthesis and no disulphide to protect. What it has instead is a glycosidic bond between nicotinamide and ribose that is primed to break, a pyridinium ring that is attacked by hydroxide, and a pyrophosphate that hydrolyses slowly in water. Those three features govern its handling and are discussed below.

The material supplied here is the free acid of β-NAD+, the naturally occurring anomer, as a lyophilised white powder in a 500 mg vial. The identifiers in the table are for the free acid; a sodium salt shows a different mass, as the section on certificates explains.

How the literature describes its mechanism

NAD+ has two distinct biological roles, and the distinction matters for interpreting the literature.

The first is the textbook one: NAD+ is a redox cofactor. A dehydrogenase transfers a hydride from its substrate to the C4 position of the nicotinamide ring, producing NADH, which is reoxidised at complex I of the respiratory chain or by lactate dehydrogenase. In this role the cofactor is not consumed; it cycles. The NAD+/NADH ratio in cytosol and mitochondria is a measure of the cell's redox state, and Houtkooper, Cantó, Wanders and Auwerx set out in 2010 how changes in that ratio feed into metabolic signalling [2].

The second role is as a substrate, and here the cofactor is consumed. Three families of enzymes cleave the glycosidic bond between nicotinamide and ribose. The sirtuins (SIRT1 to SIRT7 in mammals) use NAD+ to deacylate protein lysines, releasing nicotinamide and 2'-O-acetyl-ADP-ribose; Imai and Guarente's 2014 review is the standard account of how this couples NAD+ availability to mitochondrial biogenesis, DNA repair and circadian rhythm [3]. The poly(ADP-ribose) polymerases, of which PARP1 is the most abundant, build ADP-ribose chains on proteins at sites of DNA damage, and under genotoxic stress PARP1 can consume NAD+ fast enough to deplete the cellular pool [2]. The third family is the NAD+ glycohydrolases, principally CD38, which hydrolyse NAD+ to nicotinamide and ADP-ribose or cyclise it to cyclic ADP-ribose, a calcium-mobilising second messenger. Camacho-Pereira and colleagues in Chini's laboratory reported in 2016 that CD38 expression in mouse tissues rises with age, that CD38-knockout mice are protected from the age-related fall in tissue NAD+, and that the effect on mitochondrial function depends on SIRT3 [4].

Because the consuming enzymes release nicotinamide, the cell has to rebuild NAD+ continuously, and the main route in mammals is the salvage pathway: nicotinamide phosphoribosyltransferase (NAMPT), the rate-limiting enzyme, converts nicotinamide to nicotinamide mononucleotide (NMN), and the NMN adenylyltransferases (NMNAT1 to 3) add AMP to give NAD+. A second salvage route runs from nicotinamide riboside (NR) through the NR kinases to NMN. The de novo pathway from tryptophan and the Preiss–Handler pathway from nicotinic acid contribute less in most tissues. Covarrubias, Perrone, Grozio and Verdin's 2021 review is the most complete recent map of these routes and of the enzymes that drain the pool [1].

The quantitative picture comes from Liu and colleagues in Rabinowitz's laboratory, who used isotope tracing in mice to measure synthesis and breakdown fluxes tissue by tissue. NAD+ half-lives ranged from well under an hour to many hours depending on the tissue; circulating nicotinamide, not NMN or NR, was the main precursor delivered to tissues; and orally administered NR and NMN were largely converted to nicotinamide in the liver before reaching the rest of the body [5]. That last observation matters for the next section.

For an in-vitro programme, the direct uses of research-grade NAD+ are as a cofactor in dehydrogenase assays, a substrate for sirtuin, PARP and CD38 activity assays, a standard for NAD+ quantification by HPLC or LC-MS, and a supplement to cell-free and permeabilised-cell systems. Intact cells take up extracellular NAD+ poorly; the literature generally attributes any effect of extracellular NAD+ on cells to its breakdown by ecto-enzymes such as CD38 and CD73 into nicotinamide, NMN and NR, which are then imported and resynthesised [1].

The research record

The age-related decline. The claim that tissue NAD+ falls with age is the foundation of the field's recent growth, and it rests on a mixture of animal and human data. Massudi, Grant, Braidy and colleagues in Sydney reported in 2012 that NAD+ in human skin samples declined with age in both sexes, while PARP activity and markers of oxidative damage rose [6]. In rodents the decline has been reported in liver, muscle, adipose tissue and brain, and the CD38 work above offers a mechanism [4]. Yoshino, Baur and Imai's 2018 review assembles the evidence for the decline and for the proposition that restoring NAD+ with precursors reverses age-related phenotypes in mice [7]; Rajman, Chwalek and Sinclair's companion review in the same issue surveys the in-vivo evidence for "NAD-boosting" interventions [8]. Both are from laboratories with a stake in the hypothesis, which does not make them wrong, but a reader should know it. Covarrubias and colleagues give a more detached treatment [1].

One caution: a 2011 paper from the Sydney group on NAD+ metabolism in ageing rats was retracted by PLoS ONE in 2024 after an expression of concern in 2022. The 2012 human-tissue paper cited here [6] is a separate study and has not, to our knowledge, been the subject of any notice, but the reader may wish to weigh it accordingly.

The precursor trials. The human clinical work has almost entirely been done with precursors, not with NAD+ itself, and the distinction is the most important thing for a researcher to hold on to. Trammell, Schmidt, Weidemann and colleagues in Brenner's laboratory showed in 2016 that NR is orally bioavailable in mice and in a human subject and raises blood NAD+ metabolites, with nicotinic acid adenine dinucleotide (NAAD) as an unexpected biomarker [9]. Airhart and colleagues reported in 2017 an open-label study of nine days of oral NR in eight healthy volunteers, with roughly a doubling of whole-blood NAD+ [10]. Martens, Denman, Mazzo and colleagues published in 2018 a randomised, placebo-controlled crossover trial of six weeks of oral NR in 24 healthy middle-aged and older adults, which found it well tolerated and reported a rise of about 60% in NAD+ in peripheral blood mononuclear cells [11]. For NMN, Yoshino, Yoshino, Kayser and colleagues reported in Science in 2021 a randomised, placebo-controlled trial of ten weeks of oral NMN in 25 postmenopausal women with prediabetes, in which skeletal-muscle insulin sensitivity improved by about a quarter while most other metabolic outcomes did not change [12].

These are the strongest human data in the field, and they do not concern the dinucleotide. NR and NMN enter cells, or are converted to nicotinamide and then enter cells, before being assembled into NAD+ intracellularly [5, 7]. A researcher reading a precursor trial should not transfer its conclusions to NAD+ itself, and vice versa.

Direct administration of NAD+. The published record on the dinucleotide itself is thin. The most informative study is the 2019 pilot from Grant, Berg, Mestayer and colleagues, which measured the plasma and urine NAD+ metabolome in a small group of healthy volunteers during a six-hour intravenous infusion. The finding was pharmacokinetic rather than therapeutic: plasma NAD+ and its metabolites did not rise detectably during the first two hours, after which NAD+, nicotinamide, methylnicotinamide and ADP-ribose increased and urinary excretion rose [13]. The authors interpreted the delay as rapid tissue uptake or metabolism, but the study was small, uncontrolled and not designed to measure any clinical outcome. We cite it as a description of what happens to the molecule, not as evidence for any use.

Beyond that, the literature on administered NAD+ in humans consists of case reports and small open-label series, and no randomised controlled trial of the dinucleotide has been published. Any claim about a clinical effect of NAD+ itself is, at the time of writing, unsupported by controlled data.

Taking the record as a whole. NAD+ is one of the best-characterised molecules in biochemistry, with a century of enzymology behind it and an active literature on its decline with age and on precursors that restore it. The precursor trials are real, modest and early. The direct clinical record for NAD+ is close to empty. That is a sound basis for in-vitro research and no basis for therapeutic claims, which this page does not make.

Regulatory status in the United Kingdom

NAD+ is not a licensed medicine in the UK. It has no marketing authorisation from the MHRA, no pharmacopoeial monograph and no approved therapeutic indication. It is a naturally occurring metabolite and a standard biochemical reagent, sold in the UK by laboratory suppliers as a research chemical. BuyUK Peptides supplies it in the same way, for in-vitro laboratory use under the Terms of Sale. It is not for human or veterinary administration. Purchasers must be 18 or over and are responsible for ensuring their use of the material complies with the laws and institutional rules that apply to them. Our guide to the UK rules on research compounds sets this out in more detail.

The precursors NR and NMN are a separate regulatory matter: both are sold as food supplements in various jurisdictions, and the dinucleotide is not covered by those authorisations. Nothing on this page concerns them.

NAD+ does not appear on the World Anti-Doping Agency's Prohibited List. UK Anti-Doping's summary of the 2026 List, in force from 1 January 2026, does not mention it, and it is not named under any substance category [14]. Researchers subject to anti-doping rules should note that the List also prohibits certain methods, including intravenous infusions above a volume threshold, under category M2; that provision concerns the method rather than any substance and is noted here only for completeness.

Handling, storage and stability

NAD+ is supplied lyophilised in a glass vial with a rubber stopper and an aluminium flip-off crimp. In the dry state it is stable for years when kept cold and dry. In solution it is not, and the research literature on its instability goes back more than sixty years.

The chemistry of degradation. Lowry, Passonneau and Rock established in 1961 the pattern that still governs practice: NAD+ is stable in acid and destroyed in alkali, whereas NADH is the reverse [15]. Alkaline degradation of NAD+ proceeds by two routes. Hydroxide attacks the pyridinium ring to give adducts that rearrange and cyclise into fluorescent products, and the nicotinamide–ribose glycosidic bond hydrolyses to release nicotinamide and ADP-ribose. The second route is the one the consuming enzymes use, a reminder that the bond is intrinsically labile; the enzymes accelerate what water does slowly. A third, slower process is hydrolysis of the pyrophosphate to NMN and AMP. All three are accelerated by heat. Much of the stability literature concerns NADH, whose acid-catalysed ring hydration is a different reaction, and a reader should check which form a given paper studied.

Recent quantitative data. Wolfe and colleagues reported in 2024 a 43-day study of NAD+ and NADH in sodium phosphate, HEPES and Tris at 19 °C and 25 °C. Both cofactors were most stable in Tris; phosphate and HEPES gave faster loss, and a rise of six degrees measurably accelerated degradation over the study period [16]. The paper was written for cell-free biocatalysis, but the lesson transfers: buffer identity and a few degrees of temperature both matter over the life of a stock solution.

Sealed vial. Store at −20 °C, protected from light and moisture; 2–8 °C is acceptable for material in routine use over a few months. The powder is hygroscopic, and absorbed water both lowers the effective assay and provides the medium for hydrolysis, so allow the vial to reach room temperature before opening and reseal it promptly, ideally in a desiccator.

Reconstitution. NAD+ free acid dissolves readily in cold water to give a distinctly acidic solution, which is the regime in which the compound is most stable [15]. If the assay requires a neutral solution, adjust the pH gently with dilute sodium hydroxide or bicarbonate at the time of use and do not overshoot, because the alkaline side is where loss is fastest. Do not heat. The reconstitution calculator gives the volume to add for a target concentration; at 663.43 g/mol, 500 mg in 7.54 mL gives a 100 mM stock.

Reconstituted solution. Prepare stocks fresh, or aliquot immediately into single-use volumes and freeze at −20 °C or, better, −80 °C, where neutral solutions keep for weeks to months. Do not store solutions at room temperature. Acidic solutions in the refrigerator lose activity slowly; neutral solutions in phosphate at room temperature lose it measurably within days [16]. Discard any solution that develops a yellow colour or new fluorescence, both of which indicate ring adducts.

Checking a solution. Absorbance at 259 nm (ε about 17.4 mM⁻¹ cm⁻¹) reports total adenine-containing material and does not distinguish NAD+ from ADP-ribose or AMP. A functional check, reducing an aliquot to completion with alcohol dehydrogenase and ethanol and reading the NADH formed at 340 nm, measures only material that still works as a cofactor and is the better test of an ageing stock.

What a sound certificate for NAD+ looks like

Every batch we release carries an independent certificate of analysis, and the figures from it are transcribed on the product page and in the certificate register. Because NAD+ is a nucleotide and not a peptide, the certificate looks different from the others in the catalogue, and a reader should expect the following.

Purity by HPLC. Reversed-phase or ion-pair HPLC with UV detection at 260 nm reports the main peak as a percentage of all integrated peaks. A good batch of β-NAD+ should show 98% or above; 99% is common. The impurities to look for are the degradation products described above, nicotinamide, ADP-ribose, NMN, AMP and adenosine, and the α-anomer, which forms slowly in solution and is biologically inactive. A chromatogram is more informative than a number, because nicotinamide and AMP elute well away from the parent and their presence indicates how the batch has been stored. NADH, if present, shows at 340 nm, where pure NAD+ does not absorb.

Identity. The UV spectrum of NAD+ at neutral pH shows a single maximum at about 259 nm, an A260/A280 ratio near 4 and no absorbance at 340 nm; this is the quickest identity check and a certificate will often report it. LC-MS confirms the molecular ion: for the free acid the expected mass is 663.43 Da, seen as [M+H]+ at about m/z 664.1 or [M−H]− at about 662.1. Some certificates instead report an enzymatic assay, the fraction of the nominal mass reduced by alcohol dehydrogenase; a result close to the HPLC figure is good evidence that the material is the β-anomer and functionally intact.

Water content. Lyophilised NAD+ retains water, and the amount depends on the drying process and on handling. A certificate should report it by Karl Fischer titration or loss on drying; a few per cent is normal, and the figure should be used to correct the nominal mass when preparing solutions of accurate concentration. A high water figure is a warning that the batch has seen humidity and may already carry hydrolysis products.

Free acid or sodium salt. The free acid, which is what we supply, has the formula and mass in the table. The disodium salt has a mass about 44 Da higher and gives neutral rather than acidic solutions. The two are not interchangeable without correction: 500 mg of disodium salt contains about 6% less NAD+ by mole than 500 mg of free acid, and the forms behave differently on reconstitution, because the free acid's own acidity protects it in solution and the salt's neutrality does not [15]. A certificate should state which form was analysed, and the LC-MS mass should match it.

Our guide to reading a certificate of analysis goes through a complete report line by line.

Related compounds

NAD+ sits in the catalogue alongside two mitochondrially targeted peptides studied in the same programmes. MOTS-c, a 16-residue peptide encoded in the mitochondrial genome, has been reported to regulate metabolic homeostasis through AMPK and one-carbon metabolism, which intersects with NAD+ metabolism at several points. SS-31, a tetrapeptide that binds cardiolipin in the inner mitochondrial membrane, is studied for its effects on respiratory-chain efficiency, which an investigator will usually read out through NAD+/NADH ratios. Neither is a precursor of NAD+, and neither is handled like it; both are peptides and follow the peptide storage guidance elsewhere on this site.

Frequently asked questions

Is this the same as NR or NMN? No. Nicotinamide riboside and nicotinamide mononucleotide are precursors that cells convert into NAD+. They are different compounds with different masses, different stability and a different research literature, including the human trials described above [9, 11, 12]. Both are sold as food supplements in some jurisdictions; the dinucleotide is not, and this page says nothing about either as a supplement.

Why does the catalogue say "β-NAD"? NAD+ has two anomers at the nicotinamide–ribose bond, and only the β-anomer is a substrate for the enzymes. Commercial material is the β-form; the α-anomer appears as a minor impurity that grows slowly in stored solutions.

Why is the solution acidic? The free acid carries two phosphate protons that dissociate in water. The acidity is useful: NAD+ is far more stable in acid than in alkali [15]. Neutralise only at the point of use.

Can I store a stock solution in the fridge? For days, yes, if it is acidic. For longer, freeze single-use aliquots. Neutral solutions in phosphate or HEPES at room temperature degrade measurably within days; Tris is kinder, and cold is kinder still [16].

Are there human trials of NAD+? Of the dinucleotide itself, no controlled trial: one small pharmacokinetic pilot [13] and a scattering of uncontrolled reports. The controlled human data concern the precursors NR and NMN [11, 12].

Is it on the WADA list? No. It is not named on the 2026 Prohibited List [14].

How long does a sealed vial last? Years at −20 °C, dark and dry. The certificate reports the test date and water content; the storage guidance on this page applies from receipt.

References

1. 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. doi:10.1038/s41580-020-00313-x.
2. Houtkooper RH, Cantó C, Wanders RJ, Auwerx J. The secret life of NAD+: an old metabolite controlling new metabolic signaling pathways. Endocrine Reviews. 2010;31(2):194–223. doi:10.1210/er.2009-0026.
3. Imai S, Guarente L. NAD+ and sirtuins in aging and disease. Trends in Cell Biology. 2014;24(8):464–471. doi:10.1016/j.tcb.2014.04.002.
4. Camacho-Pereira J, Tarragó MG, Chini CCS, et al. CD38 dictates age-related NAD decline and mitochondrial dysfunction through an SIRT3-dependent mechanism. Cell Metabolism. 2016;23(6):1127–1139. doi:10.1016/j.cmet.2016.05.006.
5. Liu L, Su X, Quinn WJ, et al. Quantitative analysis of NAD synthesis-breakdown fluxes. Cell Metabolism. 2018;27(5):1067–1080.e5. doi:10.1016/j.cmet.2018.03.018.
6. 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. doi:10.1371/journal.pone.0042357.
7. Yoshino J, Baur JA, Imai S. NAD+ intermediates: the biology and therapeutic potential of NMN and NR. Cell Metabolism. 2018;27(3):513–528. doi:10.1016/j.cmet.2017.11.002.
8. Rajman L, Chwalek K, Sinclair DA. Therapeutic potential of NAD-boosting molecules: the in vivo evidence. Cell Metabolism. 2018;27(3):529–547. doi:10.1016/j.cmet.2018.02.011.
9. Trammell SAJ, Schmidt MS, Weidemann BJ, et al. Nicotinamide riboside is uniquely and orally bioavailable in mice and humans. Nature Communications. 2016;7:12948. doi:10.1038/ncomms12948.
10. Airhart SE, Shireman LM, Risler LJ, et al. An open-label, non-randomized study of the pharmacokinetics of the nutritional supplement nicotinamide riboside (NR) and its effects on blood NAD+ levels in healthy volunteers. PLoS ONE. 2017;12(12):e0186459. doi:10.1371/journal.pone.0186459.
11. Martens CR, Denman BA, Mazzo MR, et al. Chronic nicotinamide riboside supplementation is well-tolerated and elevates NAD+ in healthy middle-aged and older adults. Nature Communications. 2018;9:1286. doi:10.1038/s41467-018-03421-7.
12. Yoshino M, Yoshino J, Kayser BD, et al. Nicotinamide mononucleotide increases muscle insulin sensitivity in prediabetic women. Science. 2021;372(6547):1224–1229. doi:10.1126/science.abe9985.
13. 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. doi:10.3389/fnagi.2019.00257.
14. UK Anti-Doping. The 2026 Prohibited List: summary of changes. Published 2025, updated December 2025. ukad.org.uk.
15. Lowry OH, Passonneau JV, Rock MK. The stability of pyridine nucleotides. Journal of Biological Chemistry. 1961;236(10):2756–2759. doi:10.1016/S0021-9258(19)61730-8.
16. Wolfe KD, Alahuhta M, Himmel ME, Bomble YJ, Jennings GK, Cliffel DE. Long-term stability of nicotinamide cofactors in common aqueous buffers: implications for cell-free biocatalysis. Molecules. 2024;29(22):5453. doi:10.3390/molecules29225453.

This monograph summarises the published literature for laboratory researchers. It is not medical advice, and nothing on this site is for human or veterinary use.