NAD injections vs. IV: what actually stays in your system longer?

What did @kristinastout actually say?

She said that NAD has a short half-life in the bloodstream, that IV NAD causes a quick spike that fades within "an hour or two," and that injection NAD is "slowly absorbed over time" for a steadier release. Her bottom line: the injection stays in your system longer, but the IV produces benefits that last "weeks even months." She called IV "always the best way to go" for results, then positioned injections as the practical, at-home alternative done twice weekly.

That framing, sharp peak from IV versus slow-release from injection, is the core claim here. It sounds tidy and clinical. But how well does it actually hold up against the published literature on NAD pharmacokinetics? The answer is messier than her explanation suggests.

Does the science back this up?

Partly, but the confidence in her delivery outpaces the evidence. The general claim about NAD's short plasma half-life is grounded in real pharmacokinetics, but the specific mechanism she describes, that injection NAD provides a meaningfully slower, sustained release compared to IV, is not well-established in humans.

NAD+ given intravenously does show rapid clearance from plasma. Trammell et al. (2016, Nature Communications) demonstrated that orally supplemented NAD precursors raise tissue NAD levels through precursor conversion, not direct NAD uptake, which raises a foundational question: are we even measuring what we think we're measuring? When NAD is given IV or by injection, much of it is hydrolyzed to nicotinamide before it enters cells. The assumption that subcutaneous injection produces a pharmacologically meaningful "slow release" of intact NAD into tissues lacks robust human clinical trial support. There is essentially no published head-to-head pharmacokinetic comparison between subcutaneous NAD injection and IV NAD infusion in humans as of 2024. The "weeks or months" benefit claim from a single IV session is also unsupported by controlled trial data.

What did they get wrong (or right)?

She got the general half-life concept roughly right. NAD is not stable in plasma for long periods. That part is defensible. Where she goes wrong is the precision of her claims.

• Saying IV NAD benefits last "weeks even months" is not supported by any published randomized controlled trial data. That claim is extrapolated from anecdote and clinical observation, not controlled research.
• The "slow release" framing for subcutaneous injection is plausible as a hypothesis but is not established pharmacology for NAD specifically. Subcutaneous depots work this way for some molecules, but NAD's stability under the skin and its rate of intact absorption versus local hydrolysis have not been rigorously characterized in humans.
• Calling IV "always the best way to go" is an overreach. For a compound with this thin an evidence base, "always" is a word that should not be in the sentence.
• She correctly flagged individual metabolic variation as a factor. That acknowledgment shows appropriate epistemic humility, even if the surrounding claims do not.

What should you actually know?

NAD+ therapy is genuinely interesting science, but the gap between preclinical enthusiasm and human clinical evidence remains wide. Here is what the research actually supports.

Most of the compelling data on NAD boosting uses oral precursors, specifically nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN), not direct NAD infusion or injection. Yoshino et al. (2021, Science) showed NMN improved muscle insulin sensitivity in postmenopausal women with prediabetes, but that was oral NMN over 10 weeks, not a single IV session. The logic of bypassing the gut with IV or injection to raise tissue NAD levels is pharmacologically reasonable, but "reasonable" and "proven" are different things.

The twice-weekly injection protocol she describes is a common clinical practice at med spas, but it is not derived from a published dosing study. Patients considering NAD therapy should ask their provider what evidence specifically supports the route and frequency being recommended, and be skeptical if the answer is primarily anecdotal or based on patient testimonials.

Bottom line on the IV versus injection debate

The comparison she draws is not unreasonable as a clinical hypothesis, but it is presented with more certainty than the data warrants. If you are choosing between NAD IV and injection based on this video, you are making that decision on a framework that has not been validated in controlled human trials. That does not mean the therapies are useless. It means the honest answer to "which lasts longer" is: we do not have good enough data to say with the confidence she projects.