What is NAD+?

What is NAD+, and what does NAD stand for?

NAD+ stands for nicotinamide adenine dinucleotide, a coenzyme found in all living cells. A coenzyme is a small, non-protein organic molecule that works beside an enzyme, which is a protein that speeds up one chemical reaction. ChEBI (a curated database of small biological molecules) defines NAD+ as the oxidised form of nicotinamide adenine dinucleotide, which carries electrons from one reaction to another in metabolism (ChEBI record CHEBI:15846, checked 14 October 2026). The name lists the parts: nicotinamide, adenine and two nucleotides, which are sugar-base-phosphate units.

NAD+ is not a peptide, because no amino acid sits anywhere in its structure. The NAD+ peptide check walks through that point using PubChem, ChEBI and the wwPDB. The NAD+ research guide holds the longer literature trail, and the catalogue lists NAD+ reference material as a laboratory item, not a medicine. NAD+ in Perth covers the same molecule for the Perth catalogue.

PubChem, the U.S. National Library of Medicine’s open chemistry database, files the molecule as compound CID 5893 under the title nadide, with a molecular weight of 664.4 (PubChem, checked 14 October 2026). ChEBI lists NAD, DPN and diphosphopyridine nucleotide among its synonyms, so older papers may use those names for the same molecule.

What does NAD mean in a medical report, hospital notes or pregnancy records?

In a medical report, NAD is an abbreviation meaning “nothing abnormal discovered” or “no abnormality detected”. The NHS App help page lists NAD as nothing abnormal discovered (page last reviewed 24 March 2026). The Sydney Children’s Hospitals Network approved-abbreviation policy, effective 1 May 2024, lists NAD as No Abnormality Detected. The Queensland Health Primary Clinical Care Manual list, 12th edition, 2025, reads No abnormalities detected. The abbreviation records that an examination or test found nothing out of the ordinary. It does not refer to the molecule NAD+.

The Sydney policy states that it applies to all medical records, whether paper or electronic, in that network, so the list is not limited to one speciality; it is one example of such a list (Sydney Children’s Hospitals Network policy 2016-9005, version 3.2, effective 1 May 2024). A line that ends in NAD records what the examiner saw at that moment. It says nothing about NAD+ levels in the patient.

Meaning depends on context. The NHS App page warns that healthcare professionals sometimes use the same abbreviation to mean different things, so the surrounding note decides what a given NAD means (NHS App help, 24 March 2026). Another expansion, “no acute distress”, does not appear in any of the three lists opened for this page. Outside medicine, NAD is also the acronym of the National Association of the Deaf. Its site states a mission to preserve, protect and promote the civil, human and linguistic rights of deaf and hard of hearing individuals (nad.org, checked 14 October 2026).

A different question is whether the molecule matters in pregnancy. A 2017 study answers it from genetics, and the pregnancy and fibroids section below sets out what it found. Other uses of the letters NAD sit outside this site.

What is the structure of NAD+ and NADH?

NAD+ is built from two nucleotides, which are sugar-base-phosphate units, joined through their phosphate groups. One nucleotide carries adenine and the other carries nicotinamide. ChEBI describes NADH, the reduced form, in those terms (CHEBI:16908), and the PubChem name for NAD+ lists a 6-aminopurine (adenine), two five-membered sugar rings and a 3-carbamoylpyridin-1-ium (the nicotinamide ring). NAD+ is C21H28N7O14P2 with charge +1, and NADH is C21H29N7O14P2 with charge 0 (ChEBI, checked 14 October 2026). PubChem gives the molecular weight of NAD+ as 664.4.

Those two formulas differ by one hydrogen atom and one unit of charge. That fits NAD+ taking up a hydride, a hydrogen atom carrying an extra electron, to become NADH. In cells, NAD+ and NADH are partners: the oxidised form accepts electrons, the reduced form hands them on. Zhu et al. describe NAD as existing in the NAD+ or NADH form in all living cells (Proceedings of the National Academy of Sciences, 2015).

Think of NAD+ as an empty shuttle seat and NADH as the same seat with a passenger. The seat itself never changes; only its load does. That picture is a teaching device, not a measurement.

What is the function of NAD+ and FAD in the body?

NAD+ and FAD are both redox cofactors, helper molecules that pass electrons between enzymes. NAD+ is a coenzyme for redox reactions and is central to energy metabolism. It is also an essential partner for non-redox enzymes called sirtuins, CD38 and poly(ADP-ribose) polymerases, or PARPs (Covarrubias et al., Nature Reviews Molecular Cell Biology, 2021). FAD, flavin adenine dinucleotide, is made in cells from riboflavin (vitamin B2) and works inside flavoproteins that support energy production, redox balance and DNA repair (Balasubramaniam et al., Journal of Inherited Metabolic Disease, 2019).

Covarrubias et al. list the cell processes that NAD+ can influence directly or indirectly: metabolic pathways, DNA repair, chromatin remodelling, cellular senescence and immune cell function. Some of those enzymes use NAD+ up rather than recycling it. In cell lines, Liu et al. found NAD made from nicotinamide and consumed largely by PARPs and sirtuins, a cell-culture result that does not establish the same quantitative fluxes in a living person (Cell Metabolism, 2018).

The two molecules differ in their starting material. NAD+ is built from tryptophan or from B3-family forms, while FAD is built from riboflavin, a different vitamin (Bogan and Brenner, Annual Review of Nutrition, 2008; Balasubramaniam et al., 2019). ChEBI lists FAD’s roles as cofactor and prosthetic group (CHEBI:16238), a prosthetic group being a cofactor that stays tightly attached to its enzyme.

What are NAD levels, and how are they measured?

NAD levels are the concentrations of NAD+, NADH and related molecules measured in blood, cells or tissue. Researchers measure them with liquid chromatography coupled to mass spectrometry, an assay that separates molecules and then weighs them (Trammell and Brenner, Computational and Structural Biotechnology Journal, 2013). In 1,518 adults from the Jidong community study, average whole-blood NAD+ was 33.0 micromoles per litre, and men averaged more than women (34.5 against 31.3), in a single community sample (Yang et al., Frontiers in Endocrinology, 2022). A magnetic resonance method has also measured NAD+ and NADH in the living brains of 17 healthy volunteers; this small research-assay study does not establish a routine clinical reference range (Zhu et al., Proceedings of the National Academy of Sciences, 2015).

Methods differ, and results differ with them. In a methods study, Wang et al. built a bioluminescent sensor assay that reads NAD+ from five microlitres of fingertip blood; in 6 participants sampled twice a week over 100 days, levels were mostly stable except for one participant who started NMN, a small research-assay result that does not validate a clinical reference range (Aging Cell, 2023). Trętowicz et al. used a validated mass spectrometry system that accounts for real-world analytical variability across seven cohorts (Nature Metabolism, 2026).

A limit comes first: the sources opened for this page describe research assays, and none describes a standard clinical reference range or a routine hospital test for NAD+. A number from one assay cannot be compared with a number from another without that context.

Does NAD+ decline with age?

In pelvic skin samples from 49 people from newborns to age 77, NAD+ fell as age rose, a cross-sectional association (Massudi et al., PLoS One, 2012). In plasma from 30 healthy adults aged 20 to 87, NAD+ was lower with age, a cross-sectional association (Clement et al., Rejuvenation Research, 2019), and in a cross-sectional comparison of 12 young adults and 17 normally active older adults, muscle NAD+ was lower in the older adults, an association that is not proof that age caused the difference (Janssens et al., Nature Aging, 2022). A 2026 analysis of seven independent human cohorts found whole-blood NAD+ stable with age, a result that applies to blood and not to other tissues (Trętowicz et al., Nature Metabolism, 2026).

Tissue and sex change the picture. In the brains of 17 healthy volunteers aged 21 to 68, NAD+ and total NAD fell with age while NADH rose, a cross-sectional association that does not show a cause (Zhu et al., 2015). In whole blood from 1,518 adults in one community sample, NAD+ showed a decline trend before age 50 that disappeared after 50; in men the decrease was significant only in the group aged 60 and over, and women’s levels did not differ significantly across five age groups, a cross-sectional association from one assay (Yang et al., 2022). In a fingerstick survey of 142 healthy volunteers (75 women and 67 men), whole-blood NAD+ was higher in men than women before age 50, a cross-sectional association from one assay (Wang et al., Aging Cell, 2023).

Association is not cause. In a comparison of 17 exercise-trained older adults and 12 young adults, Janssens et al. found muscle NAD+ in the trained older adults closer to that of the young adults, but the design was cross-sectional, a one-time comparison of different people, so it cannot show that training raised NAD+ (Nature Aging, 2022). In an analysis of seven independent human cohorts, Trętowicz et al. state that their results challenge the use of whole-blood NAD+ as a biomarker of ageing, a conclusion about whole blood and not about other tissues (Nature Metabolism, 2026).

Where does the body get NAD+, and is NAD just vitamin B3 or B12?

The body makes NAD+ from several starting materials. One is the amino acid tryptophan, which the kynurenine pathway, a chain of enzymes, turns into NAD+ (Shi et al., New England Journal of Medicine, 2017). Cells also make it from forms of vitamin B3: nicotinic acid, nicotinamide and nicotinamide riboside (Bogan and Brenner, Annual Review of Nutrition, 2008). In mice, the liver makes NAD+ from tryptophan and releases nicotinamide into the blood, where other tissues use it, a tracer result in mice that does not establish the same fluxes in people (Liu et al., Cell Metabolism, 2018). NAD+ is therefore built from B3-family molecules but is not vitamin B3 itself.

Vitamin B12 is a different molecule. ChEBI describes cyanocobalamin, one form of B12, as a cobalt-centred corrin ring with the formula C63H88CoN14O14P (CHEBI:17439), while NAD+ contains no cobalt (C21H28N7O14P2).

In 12 healthy adults, nicotinamide riboside raised NAD+ in blood cells, a blood-marker result in a small group that measured no health outcome (Trammell et al., Nature Communications, 2016). In a trial of 42 healthy older men randomised to NMN or placebo, with 20 completing 12 weeks, NMN raised whole-blood NAD+, a blood-marker finding that does not itself establish a health outcome (Igarashi et al., npj Aging, 2022). This page gives no directions.

Is NMN a NAD+ supplement, and which forms have been studied in people?

NMN (nicotinamide mononucleotide) is a precursor, a molecule the body can convert into NAD+, not NAD+ itself. Human trials have mostly used precursors: nicotinamide riboside, NMN and nicotinamide. A 2026 open-label randomised study of 65 healthy adults compared them over 14 days and found that nicotinamide riboside and NMN raised circulating NAD+ comparably, while nicotinamide did not; the study measured blood NAD+ and not health outcomes (Christen et al., Nature Metabolism, 2026). A 2026 systematic review found no eligible outcomes trial of intravenous or intramuscular NAD+ for anti-ageing or wellness indications (Gallagher and Emmanuel, Ageing Research Reviews, 2026).

Animal work differs from the human work. In mice, an isotope-tracer study found that nicotinamide riboside and NMN given by one route were broken down to nicotinamide in the liver, while the same molecules given by another route reached several tissues intact, a tracer result in mice that does not establish the same distribution in people (Liu et al., 2018). Christen et al. propose that gut microbes convert both precursors to nicotinic acid, a model they supported with ex vivo fermentation experiments using human gut microbes, not with direct measurement in people (2026).

Christen et al. wrote that a direct human comparison of the precursors had been lacking before their study, and they measured blood NAD+, not health outcomes. No study opened for this page ranks forms by clinical result, so this page reports no clinical ranking from the sources it opened. This page does not list products; a product label is not evidence.

How long did NAD+ levels take to change in studies, and what is the half-life?

No single half-life for NAD+ appears in the sources opened for this page, and the timing results differ by model. In mice, NAD turned over fastest in small intestine and spleen and slowest in skeletal muscle, a mouse tracer finding that does not establish a human half-life (Liu et al., Cell Metabolism, 2018). In a one-person pilot, NAD+ in blood cells peaked about 8 hours after the participant was given nicotinamide riboside, a result that cannot be generalised from one person (Trammell et al., Nature Communications, 2016). In a pilot of 11 men, plasma NAD+ did not change until after the 2-hour sample, a small pilot (Grant et al., Frontiers in Aging Neuroscience, 2019).

Longer trials measured blood NAD+ at set visits. Whole-blood NAD+ rose at 12 weeks compared with placebo in a trial of 42 healthy older men randomised to NMN or placebo, with 20 completing 12 weeks, a blood-marker finding that does not itself establish clinical effectiveness (Igarashi et al., 2022). Blood-cell NAD+ rose after 6 weeks of nicotinamide riboside in a crossover trial of 30 healthy middle-aged and older adults randomised and 24 completing, a small trial whose blood-marker result does not itself establish a health outcome (Martens et al., Nature Communications, 2018). Circulating NAD+ rose after 14 days of nicotinamide riboside or NMN in 65 healthy adults in an open-label randomised study that measured blood NAD+ and not health outcomes (Christen et al., 2026). The 10-week NMN trial in 25 women with prediabetes also recorded NAD+ metabolites, a small single-trial measurement of a blood marker (Yoshino et al., Science, 2021).

No study opened for this page measured when anyone felt something. Those trials tracked blood markers on a clock, not sensations. Questions about how long a person might use NAD+ describe use, and this page does not answer them. In a systematic review of 33 human intervention studies, Gallagher and Emmanuel describe nicotinamide riboside and NMN as generally well tolerated over weeks to months, which cannot establish long-term or rare-event safety (Ageing Research Reviews, 2026).

What is an intravenous NAD+ drip, and what have studies of it found?

Published human data on NAD+ drips are thin. The best-described study gave NAD+ to 8 healthy men aged 30 to 55, while 3 more men received saline, and no adverse events were observed in that pilot, a group too small to estimate uncommon harms or establish general safety (Grant et al., Frontiers in Aging Neuroscience, 2019). A 2026 systematic review found no eligible outcomes trial of intravenous or intramuscular NAD+ for anti-ageing or wellness indications (Gallagher and Emmanuel, Ageing Research Reviews, 2026). A 2026 critical review concluded that intravenous longevity therapy should be regarded as an experimental intervention (Godic and Townsend, Acta Dermatovenerologica Alpina, Pannonica et Adriatica, 2026).

In Grant et al.'s 2019 pilot of 11 men (eight given NAD+, three given saline), NAD+ was rapidly and completely removed from the plasma for at least the first 2 hours under the conditions of that pilot, a small pilot that did not establish a whole-body clearance time (Frontiers in Aging Neuroscience, 2019). In Grant et al.'s pilot of eight NAD+-exposed men and three saline controls, metabolite patterns were consistent with NAD+ glycohydrolase and pyrophosphatase activity, two enzyme types that split NAD+, but this small study inferred enzyme activity rather than measuring it directly (Frontiers in Aging Neuroscience, 2019). In Grant et al.'s pilot of eight men given NAD+ and three saline controls, urine collected at 6 hours contained NAD+ and methylnicotinamide, a metabolite finding that does not establish a whole-body clearance time (Frontiers in Aging Neuroscience, 2019). The authors excluded men with a history of liver or renal failure and noted that low sample numbers may reduce sensitivity.

Godic and Townsend point to scarce, underpowered or conflicting placebo-controlled trials, pharmacokinetic limits, procedural risks and very different infusion protocols. They add that few studies used validated ageing biomarkers such as epigenetic age or telomere length. A pilot of 8 treated men cannot show how a drip behaves in other groups.

What have studies reported about side effects, and why do people feel different after NAD+?

In a crossover trial of 30 healthy middle-aged and older adults randomised, 7 participants reported 14 mild adverse events: nicotinamide riboside periods recorded one report each of nausea, skin rash, flushing, leg cramps and increased bruising, and placebo periods recorded headache (4), skin rash, flushing (2), fainting and drowsiness, in a small trial with self-reported events that cannot show which events nicotinamide riboside caused (Martens et al., Nature Communications, 2018). A 2024 systematic review of 10 randomised trials with 489 participants listed muscle pain, nervous disorders, fatigue, sleep disturbance and headache as the most common events and reported none as a serious risk, across trials of different products and short length (Gindri et al., American Journal of Physiology-Endocrinology and Metabolism, 2024).

In a 12-participant trial of nicotinamide riboside in healthy adults, two participants self-reported flushing and two self-reported feeling hot, and no serious adverse event was seen over 36 days of observation, in a small short study that cannot exclude rare or long-term harm (Trammell et al., 2016). In 40 obese men over 12 weeks, no serious adverse event was linked to nicotinamide riboside and safety blood tests were normal, in one selected group of men over a limited period (Dollerup et al., American Journal of Clinical Nutrition, 2018). In 42 healthy men aged 65 or older randomised to NMN or placebo, no serious adverse event occurred over 6 or 12 weeks, with only 20 completing 12 weeks in a trial that cannot exclude rare or long-term harm (Igarashi et al., 2022).

Why people feel good, odd or low is not explained by any study opened for this page. Personal reports after a NAD+ session are anecdote, not evidence. Covarrubias et al. list whether restoring NAD+ is safe as a question still open (2021). The groups enrolled were narrow: men aged 30 to 55, postmenopausal women with prediabetes, older men, obese men.

Evidence limits

What do reviews of human trials conclude about NAD+, and why is it debated?

A 2024 meta-analysis of 8 randomised trials with 342 mostly healthy middle-aged and older adults found no significant effect of NMN on fasting glucose, insulin or lipid markers, a result from short trials in mostly healthy adults (Chen et al., Current Diabetes Reports, 2024). Some single trials differed. In 25 postmenopausal women with prediabetes, muscle insulin sensitivity rose after NMN and not after placebo over 10 weeks, a small result in one selected group whose baseline differences were debated (Yoshino et al., Science, 2021). A published comment and the authors’ reply debated baseline differences in liver fat between the groups (Klein and Yoshino, Science, 2021). In 40 obese men, nicotinamide riboside did not improve insulin sensitivity, a result for that selected group over a short period (Dollerup et al., 2018). In a trial of 42 healthy older men randomised to NMN or placebo, with 20 completing 12 weeks, Igarashi et al. called gait-speed and grip changes nominally significant and in need of larger studies (2022).

The debate has several parts: whether blood NAD+ tracks age, whether precursors reach tissues as NAD+ or as nicotinamide, and whether raising blood NAD+ changes any outcome. That is why no single doctor’s statement settles it. This page reports review conclusions and gives no personal advice.

What have studies found about NAD+, NMN and skin ageing?

No human trial of NMN or nicotinamide riboside with a wrinkle, facial or skin-ageing outcome appeared in a PubMed search run on 14 October 2026. The following preclinical studies were found. In SKH-1 hairless mice exposed to UV-B light, NMN treatment over 10 weeks reduced wrinkle formation and skin surface roughness, a mouse result that is not evidence of a human appearance effect (Kim et al., Antioxidants, 2025), and NMN raised cellular NAD+ in cultured human skin fibroblasts, a cell-culture result that is not evidence of a human appearance effect (Kang et al., Biomedicines, 2025). A 2026 review describes skin-elasticity gains from intravenous longevity therapy only as anecdotal (Godic and Townsend, 2026).

The search combined nicotinamide mononucleotide with the terms wrinkle, facial, skin aging or photoaging and limited results to the publication types clinical trial or randomized controlled trial. It returned no records. The same search for nicotinamide riboside also returned none. A mouse result and a dish of cells cannot say what happens in a person’s face.

The trials of NAD+ precursors opened for this page measured blood chemistry, insulin clamps, grip strength and walking speed, not appearance. Photographs and personal stories are not evidence of any effect, because they lack a comparison group and a blinded assessor. The mouse paper discloses that some authors are employees of a consumer-products company, which is a fact that bears on how the paper is read.

What is known about NAD+ in pregnancy and in fibroids?

In four patients with multiple congenital malformations, Shi et al. found loss-of-function variants in HAAO or KYNU, two enzymes that make NAD+ from tryptophan, and reduced circulating NAD, a human genetic and blood observation in four patients that is not treatment evidence (New England Journal of Medicine, 2017). In engineered mice lacking those genes, Shi et al. found that embryos developed similar defects from NAD deficiency and that the defects were averted when NAD deficiency was prevented during gestation, a mouse result that does not establish a human pregnancy result (2017).

Fibroids sit in a different body of work. In human uterine leiomyoma (fibroid) tissue, drawn from 9 women who had myomectomy plus a tissue array and a public dataset of 16 patients, higher levels of NAMPT, an enzyme that regulates NAD+ metabolism, tracked with more extracellular matrix deposition and more stem-cell-like markers, an association in small tissue samples that is not a trial of NAD+ or a precursor in patients (Chiang et al., Redox Biology, 2024). In cultured fibroid cells, blocking NAMPT lowered cell viability, a cell-culture result that is not a trial of NAD+ or a precursor in patients (Chiang et al., 2024).

The authors propose NAMPT as a target for future research. A target in a dish is not a treatment in a person, and no trial opened for this page tests NAD+ in fibroids. A note reading NAD in an antenatal or gynaecology record is the clinical abbreviation covered above, not a measurement of NAD+.