NAD+ injections are not peptides: the longevity stack's category error

What NAD+ actually is

Nicotinamide adenine dinucleotide, NAD+, is one of the most important small molecules in every cell. It carries electrons in the reactions that turn food into energy, and it is consumed by enzymes that respond to the cell's state, including sirtuins, which help regulate metabolism and stress responses, and PARPs, which repair DNA. A 2018 review describes NAD+ as a redox carrier and signalling molecule controlling hundreds of processes, rising and falling with food intake, exercise and time of day, and declining with age ¹. A 2019 review adds that NAD+ is depleted by PARP activation after DNA damage and by the enzyme CD38 during chronic inflammation ².

Chemically, NAD+ is two nucleotides joined through their phosphate groups: one carrying nicotinamide, a form of vitamin B3, and one carrying adenine. It contains no amino acids, and our encyclopedia classes it as a small molecule, not a peptide ³.

Why it is sold as if it were a peptide

Walk into a longevity clinic or browse a research-peptide site and NAD+ sits on the same menu as BPC-157, MOTS-c and CJC-1295, often as an injection or an intravenous drip. The grouping is commercial: the same buyers, the same clinics, the same promise of cellular rejuvenation. Our guide to what makes a peptide explains the definitions, and why compounds such as MK-677 and orforglipron are sold as peptides too, although they are not ³.

The category error matters for more than pedantry. It blurs very different evidence bases and regulatory positions. NAD+ precursors have been tested in dozens of human trials; most research peptides have none. Intravenous NAD+ raises its own questions, quite separate from peptide injections.

Why the excitement started: the animal work

Interest in NAD+ for ageing comes from a large animal literature. The 2018 review summarises it: NAD+ declines with age, and restoring it in old or diseased animals can improve health and extend lifespan, which prompted the search for safe NAD-boosting molecules ¹. Specific studies show the range. In mice on a high-fat diet, nicotinamide riboside reduced weight gain, fatty liver, inflammation and insulin resistance, an effect that depended on the exercise hormone irisin; NR also raised irisin in human volunteers ⁴. In mice with acute metabolic acidosis, the precursor nicotinamide strongly protected kidney tubules ⁵, and in kidney injury models, an engineered delivery system that restored NAD+ synthesis improved mitochondrial function ⁶.

Those results are why NAD+ became a longevity headline. As with so much in this field, the step from mice to measurable benefits in people has proved much harder, as the human trials below show.

What the oral precursor trials show

Most human research on raising NAD+ has used precursors taken by mouth, chiefly nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN), rather than NAD+ itself. In a randomised, double-blind crossover trial in healthy middle-aged and older adults, six weeks of NR was well tolerated and effectively raised NAD+ metabolism, with initial hints about blood pressure and arterial stiffness that the authors said needed testing in larger trials ⁷. In postmenopausal women with prediabetes, ten weeks of NMN increased insulin-stimulated glucose uptake into muscle and muscle insulin signalling, measured with the gold-standard clamp method ⁸. In 30 people newly diagnosed with Parkinson's disease, 30 days of NR raised brain NAD+ levels variably, and those whose levels rose showed changes in brain metabolism associated with mild clinical improvement ⁹.

The wider picture is more sobering. A 2026 systematic review of 113 studies, 33 of them human trials, found that oral NR and NMN consistently raised NAD-related metabolites and were well tolerated over weeks to months, but that effects on functional, metabolic, vascular and other healthspan outcomes were heterogeneous and often null ¹⁰. In other words, the precursors reliably do what they are supposed to do chemically, and much less reliably do anything that a person would notice or that matters for health.

What happens to NAD+ precursors in the body

Part of the explanation may be what happens after a dose. In a 2025 mouse study, only a small part of oral NMN or NR was absorbed intact; most was converted by gut bacteria to nicotinic acid, and given intravenously, NMN and NR were rapidly broken down to nicotinamide and excreted in bile, then converted by gut bacteria ¹¹. Isotope-tracing work in mice showed that tissues differ widely in how they make and consume NAD+, and that intravenous NR or NMN were largely broken down before reaching tissues intact ¹². NAD+ itself is a large, charged molecule that does not easily cross cell membranes, which is one reason most research uses precursors rather than NAD+.

IV NAD+: the evidence gap

Intravenous and injected NAD+ is what clinics sell most aggressively, and it is where the evidence is thinnest. The 2026 systematic review found no eligible outcome trials of intravenous or intramuscular NAD+ itself for anti-ageing or wellness; one intravenous NAD+ pharmacokinetic pilot had no clinical outcomes ¹⁰.

What exists is a trial in a specific disease and clinic data on tolerability. In a 2026 randomised trial in adults with ischaemic cardiomyopathy, a seven-day course of intravenous NAD+ with standard treatment improved ejection fraction modestly at one month (45.4% against 42.4%), with non-significant trends towards fewer heart failure hospitalisations at six months ¹³. That is a single trial in heart failure, not evidence for wellness drips, and its main longer-term measures did not reach statistical significance. The patients also continued their standard heart failure treatment, which is how a drug like this would be used if it were ever approved for that purpose. A retrospective review of commercial clients given four daily infusions of NAD+ or NR found that NAD+ caused moderate to severe gastrointestinal symptoms, faster heart rate and chest pressure during infusion, which stretched infusion times to an average of 97 minutes against 37 for NR; symptoms resolved after infusion, and liver, kidney and inflammation markers did not change ¹⁴.

Regulatory status

NAD+ is not approved by FDA for any use. FDA's 503A list, updated May 14, 2026, places nicotinamide adenine dinucleotide and NAD disodium in Category 1, under evaluation, where its interim policy does not act against pharmacy compounding, while beta-nicotinamide adenine dinucleotide is in Category 3 ³. That is why compounded NAD+ injections are widely available from pharmacies, and it is a different position from most research peptides. Category 1 is a holding pattern pending FDA's evaluation, not an approval. The precursor NR is sold as a dietary supplement ³.

For athletes: the infusion rule

NAD+ itself is not named on WADA's Prohibited List, and our entry records its status as unsettled ³. But the method matters. WADA's 2026 List prohibits intravenous infusions and/or injections of more than a total of 100 mL per 12-hour period, except those legitimately received in the course of hospital treatment, surgical procedures or clinical diagnostic investigations ¹⁵. A typical wellness NAD+ drip can exceed that volume, which would make it an anti-doping rule violation regardless of what is in the bag.

Questions to ask before an NAD+ drip

• What outcome is this meant to improve, and has a randomised trial of IV NAD+ shown that it does? (For wellness and anti-ageing, the answer as of October 3, 2026 is no.)
• Where is the NAD+ from, and is it compounded by a licensed pharmacy?
• How large is the infusion, how long will it take, and what happens if I feel nauseous, flushed or develop chest pressure?
• If I am a tested athlete, is the total volume above 100 mL in 12 hours?
• Would an oral precursor, which has more trial data and fewer infusion side effects, serve the same purpose, and is there any reason to take either?

Where NAD+ fits with the mitochondrial peptides

NAD+ is often stacked with mitochondria-derived peptides such as MOTS-c and humanin, on the logic that all three support mitochondria. They are entirely different molecules with different evidence: the mitochondrial peptides have never been given to people in a published trial, while NAD+ precursors have dozens of trials with mostly modest results. Our article on humanin and the SHLPs covers the peptides. Combining them multiplies cost and uncertainty without any trial showing the combination does anything.

The bottom line

As of October 3, 2026, NAD+ is a vital coenzyme, not a peptide. Raising it with oral precursors works biochemically and is well tolerated, but benefits for health outcomes in people have been inconsistent. Intravenous NAD+ for anti-ageing or wellness has no outcome trials, often causes uncomfortable infusion symptoms, and may break anti-doping rules on volume. One trial in heart failure showed a modest short-term benefit. Nothing here is advice or a dose.

Frequently asked questions

Is NAD+ a peptide?

No. NAD+ is a coenzyme made of two nucleotides and contains no amino acids. It is sold alongside peptides by longevity clinics, but it is a small molecule.

Do NAD+ injections work?

No outcome trial supports IV or injected NAD+ for anti-ageing or wellness. A 2026 trial in ischaemic heart failure found a modest one-month improvement in heart function; that is a specific disease, not general wellness.

NMN vs NR: which raises NAD+?

Both raise NAD-related metabolites when taken by mouth and are generally well tolerated, but across 33 human trials their effects on health outcomes were mixed and often null.

What are the side effects of an NAD+ drip?

In a clinic review, IV NAD+ caused moderate to severe gastrointestinal symptoms, faster heart rate and chest pressure during infusion, which resolved afterwards but lengthened infusions.

Related on Grey Peptides

• NAD+
• What makes a peptide a peptide
• Humanin and the SHLPs

Sources

1. Rajman, L., et al. (2018). Therapeutic Potential of NAD-Boosting Molecules: The In Vivo Evidence. Cell Metab, 27(3), 529-547. PMID: 29514064
2. Braidy, N., et al. (2019). Role of Nicotinamide Adenine Dinucleotide and Related Precursors as Therapeutic Targets for Age-Related Degenerative Diseases: Rationale, Biochemistry, Pharmacokinetics, and Outcomes. Antioxid Redox Signal, 30(2), 251-294. PMID: 29634344
3. Grey Peptides encyclopedia entry for NAD+: molecule class (small molecule), FDA 503A categories (list updated May 14, 2026), supplement status of nicotinamide riboside, WADA status unsettled; molecule classes for MK-677 and orforglipron. Read October 3, 2026.
4. Li, D. J., et al. (2021). NAD(+)-boosting therapy alleviates nonalcoholic fatty liver disease via stimulating a novel exerkine Fndc5/irisin. Theranostics, 11(9), 4381-4402. PMID: 33754067
5. Bugarski, M., et al. (2021). Changes in NAD and Lipid Metabolism Drive Acidosis-Induced Acute Kidney Injury. J Am Soc Nephrol, 32(2), 342-356. PMID: 33478973
6. Lei, Y., et al. (2025). NAD(+) biosynthesis and mitochondrial repair in acute kidney injury via ultrasound-responsive thylakoid-integrating liposomes. Nat Biomed Eng, 9(10), 1740-1757. PMID: 40461655
7. Martens, C. R., et al. (2018). Chronic nicotinamide riboside supplementation is well-tolerated and elevates NAD(+) in healthy middle-aged and older adults. Nat Commun, 9(1), 1286. PMID: 29599478
8. Yoshino, M., et al. (2021). Nicotinamide mononucleotide increases muscle insulin sensitivity in prediabetic women. Science, 372(6547), 1224-1229. PMID: 33888596
9. Brakedal, B., et al. (2022). The NADPARK study: A randomized phase I trial of nicotinamide riboside supplementation in Parkinson's disease. Cell Metab, 34(3), 396-407.e6. PMID: 35235774
10. Gallagher, C., et al. (2026). NAD⁺ supplementation for anti-aging and wellness: A PRISMA-guided systematic review of preclinical and clinical evidence. Ageing Res Rev, 116, 103057. PMID: 41655607
11. Yaku, K., et al. (2025). Nicotinamide riboside and nicotinamide mononucleotide facilitate NAD(+) synthesis via enterohepatic circulation. Sci Adv, 11(12), eadr1538. PMID: 40117359
12. Liu, L., et al. (2018). Quantitative Analysis of NAD Synthesis-Breakdown Fluxes. Cell Metab, 27(5), 1067-1080.e5. PMID: 29685734
13. Yu, X., et al. (2026). Effect of Nicotinamide Adenine Dinucleotide on Heart Failure Caused by Ischemic Cardiomyopathy: A Randomized, Placebo-Controlled Trial. Am J Cardiovasc Drugs, 26(1), 97-106. PMID: 40954388
14. Reyna, K., et al. (2026). Intravenous infusion of nicotinamide adenine dinucleotide (NAD(+)) versus nicotinamide riboside (NR): a retrospective tolerability pilot study in a real-world setting. Front Aging, 7, 1652582. PMID: 41704678
15. World Anti-Doping Agency. The 2026 Prohibited List, M2.2 (intravenous infusions and/or injections of more than a total of 100 mL per 12-hour period, except in hospital treatment, surgery or clinical diagnostic investigations). Read in full July 16, 2026.

Educational information, not medical advice. Each dose in this guide names its source, an approved label or a published study. None is a recommendation for you. An unapproved compound has no established safe or effective human dose, and products sold for “research use only” are not made or tested for people. Talk to a doctor before acting on anything on this site, including before you start, stop or change any medicine or dose.