NAD+

What is NAD and what does it do in the body?

Nicotinamide adenine dinucleotide (NAD⁺) is the coenzyme of oxidation-reduction (redox) reactions in the cell and therefore sits at the center of energy metabolism. It is also a cofactor for enzymes that do non-redox work, namely sirtuins, CD38 and poly(ADP-ribose) polymerases (PARP); through this, it affects metabolic pathways, DNA repair, chromatin regulation, cellular aging (senescence) and immune cell function. ^[1]

According to the NIH niacin fact sheet, all tissues in the body convert absorbed niacin to NAD, the main active form; more than 400 enzymes require NAD, a number not seen for any other vitamin-derived coenzyme. NAD works mainly in the breakdown reactions that transfer the energy in carbohydrates, fats and proteins to ATP, the cell’s energy unit; enzymes needed to maintain genome integrity and control gene expression also use NAD. The body also converts part of the amino acid tryptophan in proteins to NAD. ^[2] The food sources, deficiency and upper limits of niacin are described in detail in the vitamin B3 guide.

According to the review by Covarrubias and colleagues, aging is accompanied by a gradual decline in tissue and cell NAD⁺ levels in many models, including rodents and humans. The authors causally link this decline to age-related diseases such as cognitive decline, cancer, metabolic disease, sarcopenia and frailty; however, the same review stresses that how to effectively restore NAD⁺ levels in aging humans, whether this is safe and whether it would provide benefit are still unknown. Some of the review’s authors have ties as company founders, advisory board members, recipients of research support from companies and holders of licensed patents related to an NMN transporter. ^[1]

Why does orally taken NAD not pass directly into cells?

According to the NIH, NAD and NADP taken with food are converted to nicotinamide in the intestine and then absorbed. ^[2] A similar barrier exists at the cellular level: Covarrubias and colleagues state that NAD⁺ cannot cross the cell membrane, so cells make NAD⁺ within themselves from precursors such as nicotinic acid, nicotinamide, nicotinamide riboside (NR) and tryptophan. For NMN, it was long thought that it had to be converted to NR by the enzyme CD73 before entering the cell; later, an NMN-specific transporter (SLC12A8), present at high levels in the small intestine, was identified. ^[1]

According to the NIH’s description, orally taken NAD enters the body not as NAD but as nicotinamide ^[2]; NAD⁺ inside the cell is also rebuilt from such building blocks. ^[1] The 2026 review summarizing human data on raising NAD also reports its findings mainly through oral NR and NMN. ^[5] The detailed evidence on precursors is covered in separate guides:

For a comparison that sets the two precursors side by side in terms of blood NAD level, human studies and regulation, see the NMN or NR? page, and for an individual assessment of the claims attributed to NMN, the NMN benefits guide.

Do precursors raise blood NAD levels, and does it translate into health?

The 2026 systematic review by Gallagher and Emmanuel, conducted with the PRISMA method, found 113 studies published between January 2010 and October 2025 that gave NAD-related compounds orally or parenterally: 33 human intervention studies (28 randomized, 5 non-randomized) and 80 rodent studies. In humans, oral NR and NMN consistently increased NAD-related metabolites in the blood (plasma or whole blood) or in cells and were generally well tolerated over weeks to months. However, effects on functional, metabolic, vascular and healthy lifespan-related outcomes were heterogeneous; mostly neutral or specific to certain measurements only. The authors wrote that raising NAD⁺ showed clear biological activity but that clinical efficacy for anti-aging or “wellness” outcomes was not established. ^[5]

The grades on this page follow this distinction: blood NAD level is a biomarker (B); clinical outcomes are inconsistent (D). The first author of the review is the owner of a company that provides administrative services to an aesthetic clinic that does not offer NAD⁺ infusion or supplements. ^[5]

What did the Parkinson’s studies show?

The largest and longest human study for NAD precursors is a Parkinson’s trial, and the result was the opposite of what was expected. NOPARK is a randomized, double-blind, placebo-controlled phase 3 study conducted at 11 centers in Norway: 410 people aged 35 and over with early-stage Parkinson’s disease diagnosed within the last 2 years were randomized, 393 entered the main analysis, and participants received oral NR or placebo for 52 weeks. The MDS-UPDRS total score rose by 2.45 points in the NR group (worsening) and fell by 0.27 points in the placebo group; the adjusted difference was 2.72 points (95% CI 0.47–4.98; p = 0.02) and favored placebo. There was no difference in four of the five prespecified key secondary outcomes, but the non-motor symptom burden worsened more in the NR group (NMSS difference 4.22 points; 95% CI 1.07–7.37). Serious adverse events occurred in 17 of 205 people (8.3%) in the NR group and 29 of 205 (14.1%) in the placebo group. The authors concluded that the findings do not support NR as a disease-modifying treatment. According to the conflict-of-interest statement, two authors hold patents licensed to an NR manufacturer and related to the use of NR in treating Parkinson’s disease. ^[6]

This result matters as a contrast: a precursor known to raise blood NAD levels did not improve clinical scores in a year-long controlled study and, on the contrary, produced a picture worse than placebo. Details are in the nicotinamide riboside guide. No such outcome study has ever been done for intravenous NAD⁺.

How much has intravenous NAD therapy been studied?

In practices offered as “NAD therapy,” “NAD serum” or “NAD infusion,” NAD⁺ itself is given intravenously or by injection. The review by Gallagher and Emmanuel found no suitable study that evaluated intravenous or intramuscular NAD⁺ itself for anti-aging or “wellness” purposes and measured outcomes. The only intravenous study meeting the criteria was a non-randomized NMN study and it mostly provided short-term safety and biomarker information; a pharmacokinetic pilot study done with intravenous NAD⁺ was evaluated only as context because it contained no clinical outcomes. The authors wrote that larger randomized studies with long follow-up that prespecify clinically meaningful outcomes are needed, especially for parenteral approaches. ^[5]

That pharmacokinetic pilot is the 2019 study by Grant and colleagues. 11 healthy men aged 30–55 without diabetes were randomized: 8 received a continuous 6-hour NAD⁺ infusion and 3 received saline (salt water). Plasma NAD⁺ and its metabolites (nicotinamide, methylnicotinamide, ADPR, NMN) did not change during the first 2 hours; the authors interpreted this as the infused NAD⁺ being rapidly and completely cleared from plasma during this time. Plasma NAD⁺ was significantly 398% above baseline only at the end of the infusion, at hour 6, and remained high 2 hours later; urinary excretion of NAD⁺ and methylnicotinamide increased. The metabolite profile was consistent with the activity of enzymes that break down NAD⁺ (NAD⁺ glycohydrolase and pyrophosphatase). ^[3]

The study is a pharmacokinetic measurement: no energy, cognition, aging or any disease outcome was measured. Its funding was provided jointly by a company focused on IV NAD⁺ research and a research institute in Australia; the study was conducted at a health center that uses IV NAD as a clinical treatment. One of the authors is an executive of this company and the center’s medical director, another received consulting fees from the company; the NAD⁺ for infusion was supplied free by a pharmacy. ^[3]

What are the side effects of NAD infusion?

In the Grant study, no adverse events were observed in either the NAD⁺ or the saline group during the 6-hour infusion; the activity of three of the liver enzymes (GGT, LD and AST) fell significantly at hour 8 and plasma bilirubin rose significantly; the authors did not consider any of these changes clinically significant. ^[3] This picture belongs to a group of 8 people who received a constant-rate infusion spread over 6 hours.

The 2026 study by Reyna and colleagues is a direct comparison from a commercial “wellness” setting. In a retrospective review of electronic records, 6 people who received intravenous NAD⁺ for 4 consecutive days and 8 people who received NR were followed for 30 days. All 6 people in the NAD⁺ group reported moderate-to-severe abdominal cramps, diarrhea, nausea, vomiting, increased heart rate, sore throat, nasal congestion and chest pressure during the infusion; the symptoms resolved immediately when the infusion ended but led participants to reduce the infusion rate. In the NR group, 5 of 8 people reported mild tingling of the tongue, jaw and arm and mild cramps. Mean infusion duration was 97 minutes with NAD⁺ and 37 minutes with NR. No adverse events (medical events) were documented in the records; ALT, AST, hsCRP, BUN/creatinine and TSH did not change, and alkaline phosphatase and HDL cholesterol fell significantly in the NAD⁺ group. ^[4]

The limits of this study are large: it is retrospective, has no placebo group, and the groups are very small. All of the authors are employees of the commercial company offering the infusions, the company funded the study, and the NR was donated by an NR manufacturer. ^[4]

Risks arising from the product itself are also on record. In the FDA’s recall records, there are 14 entries with “nicotinamide adenine” in the product description (13 NAD⁺, 1 NADH; start dates 2016–2025). The reason for 9 of them is “lack of assurance of sterility”; a recall initiated in 2025 was placed in Class I, the most serious class, on grounds of microbial contamination (elevated endotoxin) in a sterile product. The other entries relate to low potency or dissolution problems, manufacturing (GMP) deviations and labeling errors. ^[10]

How does the FDA view NAD injections in the US?

Approval status. NAD⁺ is not a drug approved by the FDA. In a warning letter dated February 9, 2026, regarding products held by a firm that repackages injectable products, the FDA stated that there was no approved application and characterized the NAD⁺ injection as an “unapproved new drug” and, because it lacked adequate directions for use, a misbranded drug. ^[9]

Pharmacy compounding (503A). In the US, pharmacies can prepare certain drugs for a patient (compounding); the FDA places bulk ingredients nominated for this purpose into categories. In the FDA’s list dated May 14, 2026, “Nicotinamide Adenine Dinucleotide (NAD)” and “NADH” are in category 1, that is, among “substances under evaluation”; a separate salt form (beta-NAD disodium salt trihydrate) is in category 3 because it was nominated without adequate support. ^[7] Category 1 is not an approval or a safety decision; it indicates that whether the substance will be placed on the list of those that can be used in compounding is being evaluated.

Raw material quality. In its announcement with a content date of October 30, 2024, the FDA stated that it was aware that some compounders were making intravenous products with food-grade NAD⁺ obtained from repackagers. The agency stated that components described as food grade are not suitable for sterile drug compounding without appropriate processing; that the risk of microbe and endotoxin contamination is high; and that this can harm patients. According to the same announcement, the FDA has received reports of side effects after injectable NAD⁺ products, such as severe shivering, vomiting and fatigue, some requiring medical treatment; the agency writes that these reactions are consistent with excessive endotoxin levels. ^[8]

What is the legal status of NAD supplements and NAD therapy in Türkiye?

Food supplements. In the September 21, 2026 version of the Ministry of Agriculture and Forestry’s Restricted Substances List for Food Supplements, the NAD family and its precursors appear on separate lines; all limits are in the maximum daily amount column for ages 11 and over: ^[12]

The list has no separate line under the name NAD⁺ (oxidized form) and no separate line for nicotinamide; vitamin B3 (niacin) appears in the section at the end of the list, “sources used before December 31, 2025,” only with the source “chemical synthesis.” ^[12] The lines have different units and substances; 20 mg for NADH and 300 mg for NR are not limits for the same molecule. The supplement approval process in Türkiye is described in the supplement regulation in Türkiye guide.

Drugs. TİTCK (Turkish Medicines and Medical Devices Agency) lists no product with NAD, NADH, nicotinamide riboside or NMN as the active ingredient in its Licensed Human Medicinal Products List dated October 16, 2026; nicotinamide appears only in multivitamin combinations. ^[13] That is, there is no licensed NAD⁺ product in Türkiye to be given intravenously or by injection.

Advertising. In a file examined at the Ministry of Trade Advertisement Board’s meeting No. 353 of January 16, 2025, it was found that social media posts by an entity authorized to operate as a “health cabin” (sağlık kabini) included “serum therapy, injection… NAD+” services and statements that NAD⁺ plays a “potential role in the prevention or treatment of neurodegenerative diseases such as Alzheimer’s and Parkinson’s.” The Board ruled that the promotions exceeded the information limit in health legislation and had the nature of advertising, and that by creating the impression that the entity was authorized in matters it was not authorized to provide services in, they were deceptive and misleading to consumers. A penalty of stopping the advertisements was imposed on grounds of violation of the Regulation on Promotion and Information Activities in Health Services (Sağlık Hizmetlerinde Tanıtım ve Bilgilendirme Faaliyetleri Hakkında Yönetmelik), the Circular on Health Cabins (Sağlık Kabinleri Hakkında Genelge), the Regulation on Commercial Advertising and Unfair Commercial Practices (Ticari Reklam ve Haksız Ticari Uygulamalar Yönetmeliği) and Article 61 of Law No. 6502. ^[14]

Is NAD infusion considered doping for athletes?

WADA’s 2026 Prohibited List does not name NAD. However, the list has a method ban: under M2.2, intravenous infusions and/or injections exceeding a total of 100 mL within a 12-hour period are prohibited at all times, in and out of competition, except those legitimately received during hospital treatment, surgical procedures or clinical diagnostic investigations. M2.2 is classified as a “Specified Method.” ^[11] This rule looks at the volume and setting of the infusion, regardless of the substance’s content.

Evidence table: claim, population and limits

This guide recommends no individualized dose, administration method or product; the numbers above are a report of study and official record results.