# What Is NAD+? What It Does in the Body and What Supplements Claim

By Ruth Calder, Enforcement Editor (https://glpwatchdog.org/authors/ruth-calder) | Published: 2026-11-04

Canonical page: https://glpwatchdog.org/research/what-is-nad-plus

> NAD+ (nicotinamide adenine dinucleotide) is a coenzyme cells use to make energy and that DNA-repair enzymes consume. The body builds it from vitamin B3 and tryptophan. Pills raise it in blood, but a 2026 review covering 33 human studies calls anti-aging benefit inconclusive.

## Key points

- NAD+ (nicotinamide adenine dinucleotide) is a coenzyme used for energy production and by enzymes involved in DNA repair.
- The body makes it from forms of vitamin B3 and the amino acid tryptophan.
- Reviews say NAD+ decreases through life, but a 2026 study of seven human cohorts found whole-blood levels stable with age.
- Oral NR and NMN reliably raise NAD-related molecules in blood; effects on health measures are often null or limited to single endpoints.
- NAD+ is not a peptide, and it is not covered by the October 2026 HHS peptide policy.

NAD+ (nicotinamide adenine dinucleotide) is a coenzyme, a helper molecule that cells use to turn food into energy and that DNA-repair enzymes burn as fuel.[1] The body builds it from forms of vitamin B3 and from the amino acid tryptophan,[2] and reviews have long said levels fall with age,[5] although a 2026 study of seven human cohorts found whole-blood levels stable.[16] Supplements and IV clinics promise to reverse that fall, but **the evidence that doing so improves health in people is inconclusive.** A 2026 systematic review, drawing on 33 human studies, concluded that oral boosters reliably raise NAD-related molecules in blood, while effects on health measures were “often null or endpoint-specific.”[7]

> **About this article.** This page explains the molecule. The trial-by-trial record on aging is in [NAD+ and longevity](https://glpwatchdog.org/research/nad-and-longevity-what-the-trials-show), and clinic drips are in [NAD+ injections](https://glpwatchdog.org/research/nad-injections-what-the-evidence-shows). Which pills raise blood levels is a separate question. Nothing here is a dose or a recommendation to take it.

## What does NAD stand for, and what is the difference between NAD+ and NADH?

NAD stands for nicotinamide adenine dinucleotide. The “nicotinamide” part is a form of vitamin B3, and “dinucleotide” means two nucleotide units joined together. Cells hold it in two forms: NAD+, the oxidized form, and NADH, the reduced form.[2] The two are the same molecule before and after it has picked up electrons, and keeping the balance between them is critical for normal cell function.[2] A related molecule, NADP, carries a phosphate group and does similar work.[3]

## What does NAD+ do in the body?

NAD+ has two broad jobs. In the first it works like a rechargeable shuttle and is not used up. In the second it is spent, then rebuilt.

*The two main jobs of NAD+*

| Job | What happens | What depends on it |
| --- | --- | --- |
| Carrying electrons | NAD+ takes electrons from food molecules and becomes NADH; NADH hands them on and returns to NAD+[1][2] | Energy metabolism, including the production of ATP, the cell’s energy currency[1] |
| Feeding other enzymes | Sirtuins, PARPs and CD38 consume NAD+ as they work, releasing nicotinamide that can be recycled[1][2] | DNA repair, gene regulation, cell aging and immune cell function[1] |

That second job is why NAD+ draws so much interest in aging research. The enzymes that use it sit close to processes that wear down over a lifetime, so a shortage has an obvious theoretical cost. A plausible theory is a starting point, and the authors of a leading review note that much remains to be learned about how NAD+ affects human health and aging.[1]

## Where does the body get NAD+?

You do not need to swallow NAD+ to have it. Cells make it through three routes: one starts from the amino acid tryptophan, one from nicotinic acid, and the salvage pathway recycles nicotinamide and related molecules, including the nicotinamide released when enzymes use NAD+ up.[2] Diet supplies the raw materials. Niacin, the name for vitamin B3, is found in milk, eggs, enriched breads and cereals, rice, fish, lean meats, legumes, peanuts and poultry.[4]

The recommended intake for adults is 16 mg a day for men and 14 mg a day for women, higher in pregnancy and while breastfeeding.[4] A true deficiency causes pellagra, with digestive problems, inflamed skin and poor mental function.[4] The supplements sold today are a different proposition: they aim to push NAD+ above the level a normal diet supports.

*The molecules sold or studied as NAD+ boosters*

| Molecule | What it is | How it is usually sold |
| --- | --- | --- |
| Nicotinamide (Nam) | A form of vitamin B3[3] | Supplement |
| Nicotinic acid (niacin) | A form of vitamin B3[2] | Supplement; also studied at high doses |
| Nicotinamide riboside (NR) | A precursor the body converts to NAD+[3] | Supplement |
| Nicotinamide mononucleotide (NMN) | A precursor the body converts to NAD+[3] | Supplement |
| NAD+ itself | The finished coenzyme | IV drip or injection from clinics[7] |

## Does NAD+ decline with age?

Not clearly, at least in blood. A 2023 review by endocrinologists and aging researchers states that NAD+ levels decrease throughout life and that this decline has been postulated to contribute to age-related disease.[5] The word “postulated” matters. A 2019 trial report described the decline as shown in preclinical models, with sparse human data.[6] Another review calls lower NAD+ a hallmark of aging while conceding that the underlying causes remain unclear.[2]

A 2026 study tested the premise directly. Researchers measured whole-blood NAD+ across seven independent human cohorts and found it stable with age and across lifestyle programs, although it did respond to nicotinamide riboside. They said the result challenges the use of blood NAD+ as a marker of aging.[16] Blood is not muscle or brain, so this leaves open what happens inside other tissues. Raising NAD+ improved metabolism, heart function and healthspan in model animals,[5] and human trials exist to test whether any of that carries over.

## What do NAD supplements claim, and what do the trials show?

The claims on labels and clinic pages usually concern energy, metabolism, muscle and aging. Human trials support only part of the chain. Pills raise NAD-related molecules in blood.[7] Whether that changes how a person feels or functions is the unresolved part.

*NAD+ claims against human evidence, November 2026*

| Claim | What human studies found |
| --- | --- |
| Raises NAD+ | Yes for oral NR and NMN, consistently, in blood and cells[7] |
| Slows aging | Clinical effectiveness for anti-aging or wellness outcomes remains inconclusive[7] |
| Improves blood sugar | One 10-week NMN trial improved muscle insulin sensitivity in women with prediabetes;[8] pooled NMN trials found no significant benefit on glucose, insulin or lipids[10] |
| Preserves muscle | A 2025 meta-analysis found the evidence does not support NMN or NR for muscle mass and function in adults averaging over 60[9] |
| Slows Parkinson disease | In a 52-week phase 3 trial of NR in 410 people with early disease, rating scores ended 2.72 points worse than placebo on a 236-point scale, and the authors said the findings do not support it as a treatment[17] |
| IV drips work better than pills | No eligible outcome trial has tested IV or injected NAD+ for anti-aging or wellness[7] |

Clinic drips get their own caution. A pilot study of a six-hour NAD+ infusion measured what happened to it in the blood,[11] and the 2026 review found no eligible outcome trial of IV or injected NAD+ for anti-aging or wellness.[7] The difference between an infusion and a capsule is set out in [NAD+ vs NMN](https://glpwatchdog.org/research/nad-plus-vs-nmn). If tiredness on a GLP-1 is what brought you here, the common causes are in [fatigue on a GLP-1](https://glpwatchdog.org/research/glp1-fatigue-what-causes-it), and they have little to do with NAD+.

## Is NAD+ a peptide, and is it FDA-approved?

NAD+ is not a peptide. [Peptides are chains of amino acids](https://glpwatchdog.org/research/what-are-peptides), and NAD+ is built from nucleotides. It turns up on peptide menus because clinics sell it beside them, a grouping explained in [what is peptide therapy](https://glpwatchdog.org/research/what-is-peptide-therapy). The HHS policy announced on October 28, 2026 names six peptides, and NAD+ is not among them.[14]

FDA’s list of substances nominated for 503A compounding, as updated May 14, 2026, places NAD and NADH in Category 1, the group still under evaluation.[13] Being on that list is not an approval and says nothing about whether it works. Sellers and status are on our [NAD+ profile](https://glpwatchdog.org/peptides/nad).

## Is NAD+ safe?

In short trials, oral NR and NMN were generally well tolerated over weeks to months.[7] Long-term data are limited. Drips are less comfortable: in a 2026 retrospective review of records from a commercial clinic, people given IV NAD+ reported moderate to severe stomach symptoms, a faster heart rate and chest pressure during the infusion, which resolved when it ended.[12]

Two broader cautions apply to vitamin B3 itself. Too much niacin can raise blood sugar and cause liver damage, peptic ulcers and skin rashes.[4] And a 2024 study of cardiac patients linked high blood levels of two breakdown products of excess niacin, 2PY and 4PY, to a higher three-year risk of major cardiac events.[15] That was an association in people who already had a heart condition, and it did not test NAD+ supplements, but it is a reason not to assume that more is harmless.

## Frequently asked questions

### What is NAD?

NAD, short for nicotinamide adenine dinucleotide, is a helper molecule inside cells. It helps turn food into energy and is used by enzymes involved in DNA repair and gene regulation. NAD+ and NADH are its two forms, before and after it picks up electrons.

### What does NAD+ do for your body?

It carries electrons during energy production and acts as fuel for enzymes such as sirtuins and PARPs, which take part in DNA repair and cell maintenance. Those are its normal roles. Taking extra has not been shown to improve health in the same way.

### Is NAD+ the same as niacin?

No. Niacin is vitamin B3, one of the raw materials the body uses to build NAD+. Adults are advised to get 16 mg a day (men) or 14 mg a day (women) from food. NAD+ is the finished coenzyme made inside cells.

### Is NAD a peptide?

No. Peptides are chains of amino acids, and NAD+ is built from nucleotides. Clinics often list it on peptide menus, but it is not covered by the October 2026 HHS peptide compounding policy.

### Do NAD supplements work?

They do raise NAD-related molecules in the blood. Across 33 human studies, a 2026 systematic review saw effects on function, metabolism and blood vessels that were often null or limited to single measures, and it called anti-aging effectiveness inconclusive.

## 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. PMID: 33353981. DOI: 10.1038/s41580-020-00313-x. https://pubmed.ncbi.nlm.nih.gov/33353981/
2. Amjad S, Nisar S, Bhat AA, Shah AR, et al. Role of NAD(+) in regulating cellular and metabolic signaling pathways. Molecular Metabolism. 2021. PMID: 33609766. DOI: 10.1016/j.molmet.2021.101195. https://pubmed.ncbi.nlm.nih.gov/33609766/
3. Christen S, Redeuil K, Goulet L, Giner MP, et al. The differential impact of three different NAD(+) boosters on circulatory NAD and microbial metabolism in humans. Nature Metabolism. 2026. PMID: 41540253. DOI: 10.1038/s42255-025-01421-8. https://pubmed.ncbi.nlm.nih.gov/41540253/
4. MedlinePlus, National Library of Medicine Niacin. MedlinePlus Medical Encyclopedia. 2026. https://medlineplus.gov/ency/article/002409.htm
5. Bhasin S, Seals D, Migaud M, Musi N, Baur JA. Nicotinamide Adenine Dinucleotide in Aging Biology: Potential Applications and Many Unknowns. Endocrine Reviews. 2023. PMID: 37364580. DOI: 10.1210/endrev/bnad019. https://pubmed.ncbi.nlm.nih.gov/37364580/
6. Elhassan YS, Kluckova K, Fletcher RS, Schmidt MS, et al. Nicotinamide Riboside Augments the Aged Human Skeletal Muscle NAD(+) Metabolome and Induces Transcriptomic and Anti-inflammatory Signatures. Cell Reports. 2019. PMID: 31412242. DOI: 10.1016/j.celrep.2019.07.043. https://pubmed.ncbi.nlm.nih.gov/31412242/
7. Gallagher C, Emmanuel OO. NAD⁺ supplementation for anti-aging and wellness: A PRISMA-guided systematic review of preclinical and clinical evidence. Ageing Research Reviews. 2026. PMID: 41655607. DOI: 10.1016/j.arr.2026.103057. https://pubmed.ncbi.nlm.nih.gov/41655607/
8. Yoshino M, Yoshino J, Kayser BD, Patti GJ, et al. Nicotinamide mononucleotide increases muscle insulin sensitivity in prediabetic women. Science. 2021. PMID: 33888596. DOI: 10.1126/science.abe9985. https://pubmed.ncbi.nlm.nih.gov/33888596/
9. Prokopidis K, Moriarty F, Bahat G, McLean J, et al. The Effect of Nicotinamide Mononucleotide and Riboside on Skeletal Muscle Mass and Function: A Systematic Review and Meta-Analysis. Journal of Cachexia, Sarcopenia and Muscle. 2025. PMID: 40275690. DOI: 10.1002/jcsm.13799. https://pubmed.ncbi.nlm.nih.gov/40275690/
10. Chen F, Zhou D, Kong AP, Yim NT, et al. Effects of Nicotinamide Mononucleotide on Glucose and Lipid Metabolism in Adults: A Systematic Review and Meta-analysis of Randomised Controlled Trials. Current Diabetes Reports. 2024. PMID: 39531138. DOI: 10.1007/s11892-024-01557-z. https://pubmed.ncbi.nlm.nih.gov/39531138/
11. Grant R, Berg J, Mestayer R, Braidy N, 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. PMID: 31572171. DOI: 10.3389/fnagi.2019.00257. https://pubmed.ncbi.nlm.nih.gov/31572171/
12. Reyna K, Heinzen G, Patel N, Ritter M, et al. Intravenous infusion of nicotinamide adenine dinucleotide (NAD(+)) versus nicotinamide riboside (NR): a retrospective tolerability pilot study in a real-world setting. Frontiers in Aging. 2026. PMID: 41704678. DOI: 10.3389/fragi.2026.1652582. https://pubmed.ncbi.nlm.nih.gov/41704678/
13. U.S. Food and Drug Administration Bulk Drug Substances Nominated for Use in Compounding Under Section 503A of the Federal Food, Drug, and Cosmetic Act (updated May 14, 2026). FDA. 2026. https://www.fda.gov/media/94155/download
14. U.S. Department of Health and Human Services HHS Enforcement Discretion Policy Regarding 503A Compounding Using Certain Peptide Bulk Drug Substances (with Appendix A and Appendix B). HHS. 2026. https://www.hhs.gov/sites/default/files/hhs-503a-peptide-enforcement-discretion-policy-appendix-b.pdf
15. Ferrell M, Wang Z, Anderson JT, Li XS, et al. A terminal metabolite of niacin promotes vascular inflammation and contributes to cardiovascular disease risk. Nature Medicine. 2024. PMID: 38374343. DOI: 10.1038/s41591-023-02793-8. https://pubmed.ncbi.nlm.nih.gov/38374343/
16. Trętowicz MM, Scantlebery AML, Schomakers BV, Eroğlu KD, et al. Human whole-blood NAD(+) levels do not vary with age or lifestyle interventions. Nature Metabolism. 2026. PMID: 42135539. DOI: 10.1038/s42255-026-01537-5. https://pubmed.ncbi.nlm.nih.gov/42135539/
17. Brakedal B, Skeie GO, Derad C, Alstadhaug KB, et al. Nicotinamide Riboside for Patients With Early-Stage Parkinson Disease: The NOPARK Randomized Clinical Trial. JAMA. 2026. PMID: 42848371. DOI: 10.1001/jama.2026.18828. https://pubmed.ncbi.nlm.nih.gov/42848371/

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Cite as: GLP Watchdog, Ruth Calder, "What Is NAD+? What It Does in the Body and What Supplements Claim", published 2026-11-04. https://glpwatchdog.org/research/what-is-nad-plus

Canonical HTML page: https://glpwatchdog.org/research/what-is-nad-plus

Medical disclaimer: Nothing here is medical advice. We report on this subject; we do not treat anyone. Whether to begin a medication, supplement, or treatment, whether to adjust it, and whether to stop are questions for a clinician licensed to answer them, who knows your history.