NAD+ Injections: What the Human Evidence Actually Shows (2026)

NAD+ injections and IV drips have become one of the most reliably profitable items on a longevity clinic's menu, sold for energy, recovery, cognition and slowing the clock. The underlying biology is not made up: NAD+ is a genuinely central cofactor in cellular energy metabolism, and its decline with age is a real and well-documented observation¹.

The problem is what sits between that observation and the injection. And a 2026 systematic review answered that question about as directly as a review ever does.

The headline: no outcomes trial has evaluated injected or infused NAD+ itself for anti-aging or wellness. Not a negative trial — no eligible trial. That is the state of the evidence for the thing being sold, and everything below is the detail behind it.

What the systematic review found

A PRISMA-guided systematic review published in Ageing Research Reviews examined human and rodent intervention studies of NAD-related compounds administered orally or parenterally between January 2010 and October 2025. It identified 113 eligible studies: 33 human intervention studies (28 randomised) and 80 rodent studies¹.

Its conclusions split cleanly in three:

In rodents, NAD+ augmentation was frequently associated with improvements in metabolic, mitochondrial, inflammatory and functional outcomes — though effects varied across models and endpoints¹. This is where the enthusiasm comes from, and it is not nothing.

In humans, with oral precursors, nicotinamide riboside and nicotinamide mononucleotide consistently demonstrated biochemical target engagement — measurable rises in circulating or cellular NAD-related metabolites — and were generally well tolerated over weeks to months. But effects on functional, metabolic, vascular and other healthspan-relevant outcomes were heterogeneous and often null or endpoint-specific¹.

In humans, with injected or infused NAD+ itself — the actual product in a clinic — the review found no eligible outcomes trials at all. One non-randomised intravenous NMN study met inclusion criteria and contributed short-term safety and biomarker information; an intravenous NAD+ pharmacokinetic pilot lacking eligible clinical outcomes was noted only as contextual evidence¹.

Read that last paragraph again in the context of the price of an IV drip.

The pattern underneath: the marker moves, the outcome doesn't

The oral-precursor literature is worth dwelling on, because it is the strongest human evidence in this space and it demonstrates the failure mode with unusual clarity.

Nicotinamide riboside does what it says biochemically. A study in aged human skeletal muscle showed NR supplementation augmenting the muscle NAD+ metabolome and inducing transcriptomic and anti-inflammatory signatures². In a randomised crossover trial in overweight and obese volunteers, six weeks of NR at 1,000 mg/day raised markers of increased NAD+ synthesis in skeletal muscle, increased fat-free mass and sleeping metabolic rate, and increased muscle acetylcarnitine concentrations³. Target engagement is not in doubt.

Now the functional endpoints. In a randomised physiologic study, 30 overweight or obese adults aged 45 or over received an NMN preparation or placebo for 28 days. NAD and its metabolites rose substantially, and body weight, diastolic blood pressure, total cholesterol and LDL cholesterol all improved significantly more than placebo. But changes in muscle strength, muscle fatigability, aerobic capacity and stair-climbing power did not differ significantly between groups⁴.

And when the functional question is asked across the literature at once, the answer is unambiguous. A 2025 systematic review and meta-analysis in the Journal of Cachexia, Sarcopenia and Muscle pooled randomised trials of NMN and NR against placebo in adults with a mean age from 60.9 to 83. NMN showed no significant effect on skeletal muscle index, handgrip strength, gait speed or the five-time chair stand test, and the narrative synthesis found no improvement in knee extension strength, the short physical performance battery, or thigh muscle mass. The authors' conclusion: current evidence does not support NMN and NR supplementation for preserving muscle mass and function in adults over 60⁵.

That is a coherent body of work with a consistent shape. The biochemistry works. The performance doesn't follow.

Why injecting it doesn't obviously fix this

The intuitive case for an injection is that it bypasses digestion and delivers more. Two things complicate that.

First, the oral-precursor trials above already achieved target engagement. NAD levels went up, measurably, repeatedly²³⁴. If raising the marker were sufficient, those trials would have produced the functional benefits — and largely they did not. A delivery route that raises the same marker higher is answering a question that does not appear to be the bottleneck.

Second, NAD+ is a large, charged molecule, and cells do not simply take it up whole from the bloodstream; the salvage and precursor pathways exist because that is how the system is actually supplied. Whether circulating NAD+ from an infusion reaches the intracellular compartments that matter is a genuine open question rather than a settled mechanism — which is precisely why the absence of an outcomes trial matters so much. There is no empirical result to fall back on.

What is actually known about the injections

Very little, and it is worth being exact about the shape of that ignorance rather than converting it into either endorsement or alarm.

The review found short-term safety and biomarker information from one non-randomised intravenous NMN study, plus a pharmacokinetic pilot for intravenous NAD+ that had no eligible clinical outcomes¹. Anecdotally, IV NAD+ infusions are widely reported to cause chest tightness, nausea and flushing when run quickly, which is why clinics infuse slowly — but "widely reported" is not a controlled adverse-event rate, and the honest statement is that no trial has produced one.

There is also a supply-quality question that applies to every injectable in this market. Compounded NAD+ preparations are not FDA-approved products, and the wider analytical literature on peptides and injectables purchased outside the prescription system has repeatedly found low purity and contamination — the detail is in are peptides bad for you? and our guide to verifying a certificate of analysis.

Where this fits against the rest of the category

NAD+ has an unusually clean version of a problem that runs through everything on this site: a real mechanism, confirmed target engagement, and outcomes that do not follow.

The closest parallel is the GH axis, where releasing peptides reliably raise growth hormone and IGF-1 and then fail to deliver the body-composition benefit that was supposed to follow — we cover that in GH peptides and recovery. The compound most often sold alongside NAD+ claims is 5-Amino-1MQ, whose NNMT mechanism is pitched as an indirect route to sparing NAD+; we take that specific pathway apart in does 5-Amino-1MQ boost NAD+? and grade the compound overall in is 5-Amino-1MQ legit?. And for the broader question of which goals in this space have evidence behind them at all, see what are peptides good for?.

One note for anyone drug-tested: NAD+ itself is not the concern, but the longevity clinics selling it typically sell sermorelin and other GH-axis peptides from the same menu, and those are banned in tested sport, year-round, with a prescription changing nothing. Check specific compounds with our prohibited-substance checker.

The bottom line

NAD+ declines with age. Oral precursors raise it. Rodents given NAD+ boosters improve on a range of measures. All three of those statements are true and all three are used to sell an injection that none of them is about.

The trial that would justify the injection — NAD+ administered parenterally, measured against placebo, on an outcome a person could feel — has not been run. Meanwhile the closest available evidence, from oral precursors that successfully raised the marker, found the functional benefits heterogeneous and often absent, and a meta-analysis in older adults found nothing for muscle mass or function at all¹⁵.

That is not proof an NAD+ injection does nothing. It is the more specific and more useful finding that after fifteen years and 113 studies, nobody has produced evidence that it does something — and that a clinic charging for one is selling rodent data and a plausible mechanism, at a price that implies considerably more.