A molecule enters a vein, but its concentration in the sampled blood does not immediately rise. Where did it go? That was one of the puzzles in a small 2019 human study of intravenous NAD+: plasma levels did not increase significantly during the first two hours, then were elevated at the six-hour measurement.[1] Following that puzzle leads to a more useful discussion than treating an infusion as a cellular refill. Blood measurements, changes inside cells and improvements in how someone feels or ages are different outcomes. Establishing one does not automatically establish the others.
Essential biology is the starting point
Nicotinamide adenine dinucleotide, abbreviated NAD+, participates in energy metabolism and is used in processes including DNA repair and cellular signaling.[1] Its role explains scientific interest in how the body makes, consumes and recycles it. It does not answer whether supplying more through an infusion improves a particular person's health.
The names can add confusion. NAD+, nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN) are distinct compounds connected through metabolic pathways; NR and NMN are investigated as NAD+ precursors.[1] Their relationship does not make their preparations or results interchangeable. A finding about one compound, delivered through one route, needs an evidentiary bridge before it can support a claim about another.
Grant and colleagues' 2019 paper investigated the fate of infused NAD+ through measurements of NAD+ and related metabolites, the molecules formed or used as metabolism proceeds.[1] It was a human study, and its full text was reviewed for this article. It was not a clinical anti-aging outcome trial: its measurements did not establish longer life, improved cognition or sustained functional improvement.[1]
Eleven volunteers and an eight-hour window
The investigators recruited 11 men aged 30–55, randomly assigning eight to NAD+ and three to saline control.[1] Infusions lasted six hours, with blood and urine measurements extending to eight hours after the start; participants were selected under criteria excluding several significant medical conditions.[1] That design gives the study a precise scope. It cannot represent all ages, women, people with the excluded conditions or repeated treatment over months.
The investigators reported no observed adverse events during the six-hour infusion in either group.[1] That is reassuring evidence about what happened to these participants under these conditions. Eight exposed participants and a brief observation period cannot establish universal safety or reliably rule out uncommon or delayed problems.
Several laboratory markers changed by the eight-hour measurement, including a small bilirubin increase; the authors considered the changes not clinically significant.[1] The discussion suggested possible favorable implications from reductions in some enzyme activities, but those observations should not be converted into demonstrated liver repair or a general health benefit.[1] The actual measurements and their clinical interpretation need to remain separate.
Disappearing from plasma is not proof of cellular restoration
Plasma is the liquid portion of blood. The study found no significant early plasma NAD+ rise, followed by a significant increase at six hours that remained evident at eight hours; several related metabolites also changed.[1] Urinary excretion of NAD+ and methylnicotinamide increased, while urinary nicotinamide did not show a significant rise.[1] These results show that the infusion affected the measured chemistry, but a blood or urine result does not locate every molecule throughout the body.
The authors interpreted the early pattern as rapid removal from plasma through uptake and/or metabolism.[1] That is an interpretation of the measured concentrations, not direct proof that NAD+ entered all relevant cells or restored their internal pools. The paper itself identified further measurements, including red-cell metabolites and additional metabolic products, as useful next steps.[1]
| Observation or claim | What the study supports | What it does not establish |
|---|---|---|
| No significant early plasma rise | A measured concentration pattern during the first two hours.[1] | Where every molecule went or complete intracellular restoration. |
| Higher plasma NAD+ at six hours | A change in a sampled blood compartment.[1] | Reversal of aging or improved everyday function. |
| Changes in urinary metabolites | Evidence relevant to metabolism and excretion.[1] | A complete account of tissue uptake. |
| No observed infusion adverse events | Short-term reassurance in this small selected group.[1] | Safety across products, populations or repeated use. |
The study was jointly funded by NAD+ Research Inc. and the Australasian Research Institute Incorporation, and the NAD+ supply was provided without charge by Archway Apothecary.[1] One author was a director of NAD+ Research Inc. and medical director of the treatment center; another reported consulting fees from NAD+ Research Inc.[1] Those disclosures do not invalidate the measurements. They are relevant context when weighing interpretation and the need for independent replication.
Why the FDA alert belongs beside the reassuring result
In an October 2024 alert, FDA said it was aware of compounders using food-grade NAD+ to make intravenous products, warning that such ingredients were unsuitable for sterile compounding without appropriate processing because of microbial and endotoxin contamination risks.[2] FDA also reported adverse-event submissions involving severe chills, shaking, vomiting and fatigue, with some cases requiring medical treatment; it described these reactions as consistent with excessive endotoxins.[2]
“Consistent with” matters. The alert reports a suspected explanation, not proof that every NAD+ product is toxic or that NAD+ itself caused every reaction. It also does not negate the pilot study's observed tolerability: the products, participants and evidence are different.[1][2] Together, these sources show why evaluating the molecule and evaluating an injectable preparation are separate tasks.
A research vial is not a clinical conclusion
Approved medicines, clinical-trial preparations, compounded products and research reagents are distinct contexts. Neither participation in a study nor mention in a compounding alert, by itself, establishes an approval decision or the legal status of every product bearing the name NAD+.[1][2]
FDA's June 2026 letter concerning Prostamax and Gonadorelin explains that research labeling did not override evidence of human-use marketing and describes the general risks of injections bypassing defenses against toxins and microorganisms.[3] It contains no product finding about NAD+ or Chudik materials.
A research label or chemical-purity figure alone cannot establish medicinal equivalence, microbiological quality, resulting exposure or suitability for human use. This is why research materials should not be consumed or self-administered, without assuming every vial is contaminated or untested.
The 2019 study makes a useful contribution to understanding NAD+ metabolism. Its most responsible lesson is to follow the measurements carefully: a molecule's essential role and a change in blood chemistry are starting points for clinical investigation, not completed proof of an anti-aging benefit.[1]