NAD+

NAD+ does two jobs. As a redox cofactor it shuttles electrons through glycolysis, the TCA cycle and oxidative phosphorylation — this is bulk metabolism, and the cell keeps it tightly buffered. As a consumed substrate it feeds the sirtuin deacetylases, the PARP DNA-repair enzymes and the ectoenzyme CD38, all of which cleave NAD+ and destroy it in the process. Tissue NAD+ falls with age, largely because CD38 expression rises with inflammation, and that decline is the premise of the whole NAD+ industry. The unresolved question is delivery: NAD+ is a large charged molecule that does not cross cell membranes intact, so intravenous NAD+ is substantially degraded to nicotinamide and other metabolites before it reaches the inside of a cell. Whether IV NAD+ outperforms simply taking an oral precursor like NR or NMN has never been demonstrated in a controlled trial.

Targets: Sirtuins (SIRT1-7), PARP1, CD38, Electron transport chain complex I

• · 50-100 mg per injection is the current clinic norm. Subcutaneous NAD+ stings noticeably; dilute it and inject slowly. This route is cheaper, self-administrable and produces a flatter curve than IV.
• · 250-1000 mg in saline. Pushing the drip rate to shorten the session is the single most common cause of the chest tightness and nausea people describe.

Work out your exact syringe units →

• very commonChest tightness, flushing and inner restlessness during IV infusion— Rate-dependent and the defining experience of an NAD+ drip. Slowing the infusion resolves it within minutes.
• very commonNausea— Also rate-dependent.
• very commonInjection-site burning and redness (subcutaneous)— The acidity of the solution, not an allergy. Dilute more.
• commonHeadache
• commonInsomnia if dosed late in the day
• uncommonMuscle cramping during infusion

• Active malignancy — NAD+ availability supports the biosynthesis and DNA-repair capacity of proliferating cells, and this is a genuinely open question rather than a boilerplate caution.
• Pregnancy and breastfeeding — no data.
• Unmonitored IV administration at home; the infusion reaction is common enough that someone should be present.

• redundantnmn-nr-precursors — Oral NMN or NR feeds the same salvage pathway. Running both is largely paying twice for one effect.
• synergyss-31 — Commonly paired — cofactor supply plus membrane structure. Plausible, untested.
• synergyresveratrol — The classic sirtuin-activation pairing, though the resveratrol side of that story has weakened considerably.

• · Blood pressure and heart rate during infusion.
• · Liver enzymes if you are running high-dose protocols repeatedly.
• · Whole-blood NAD+ assays exist commercially but are poorly standardised — do not over-interpret them.

NAD+ is sold as a supplement ingredient and compounded by clinics for injection in the US; injectable NAD+ is not an FDA-approved drug and its compounding status has been contested.

• Martens et al. 2018, Nature Communications — chronic nicotinamide riboside supplementation in healthy middle-aged and older adults (trial)
• Elhassan et al. 2019, Cell Reports — nicotinamide riboside augments the human skeletal muscle NAD+ metabolome (trial)
• Covarrubias et al., review of NAD+ metabolism in ageing and disease (review)

NAD+ does two jobs and the distinction between them is the key to understanding why the supplementation story is weaker than it sounds. As a redox cofactor it shuttles electrons through glycolysis, the TCA cycle and oxidative phosphorylation, cycling between NAD+ and NADH without being consumed. That pool is enormous, tightly buffered, and not plausibly limiting in a healthy person — you do not run out of an electron carrier. As a consumed substrate it feeds three families of enzyme that cleave the glycosidic bond and destroy the molecule: the sirtuin deacylases, the PARP DNA-repair enzymes, and the ectoenzyme CD38. This is the pool that matters for ageing, and the mechanism of age-related NAD+ decline is now reasonably well understood to be driven substantially by rising CD38 expression in the setting of chronic low-grade inflammation, alongside increased PARP activity from accumulated DNA damage. So the correct framing is that NAD+ falls with age largely because consumption rises, not because synthesis fails. That has an uncomfortable implication for the intervention: pouring in more substrate when the problem is an overactive consumer is a different and less efficient strategy than inhibiting the consumer. The delivery problem compounds it. Intravenous NAD+ is degraded extracellularly to nicotinamide and riboside species before it can reach an intracellular compartment, which means an NAD+ drip is, pharmacologically, an expensive and uncomfortable way to deliver nicotinamide precursors that you could have taken by mouth. The human trial literature is consistent with that reading: oral NR and NMN reliably raise blood NAD+ — Martens 2018 showed this cleanly in middle-aged and older adults — and have largely failed to move hard clinical endpoints. Meanwhile intravenous and subcutaneous NAD+, the routes that clinics actually sell, have essentially no controlled trial data at all. The acute effects people describe during a drip — chest tightness, flushing, inner restlessness, nausea — are rate-dependent and resolve within minutes of slowing the infusion, which is a strong hint that they are a pharmacological reaction to bolus delivery rather than a therapeutic sensation.

The infusion reaction is the thing that goes wrong most visibly and it is almost always self-inflicted. Chest tightness, flushing, nausea, muscle cramping and an unpleasant inner restlessness are rate-dependent, and the single most common cause is a clinic pushing the drip faster to shorten the appointment. The fix is trivial: slow it down and it resolves in minutes. People power through it because they assume it is the drug working. It is not. The second failure is the subcutaneous burn — NAD+ solutions are strongly acidic, and the answer is more dilution volume and slower injection rather than a smaller dose or a different vendor. The third is the money-versus-evidence problem, and it is the big one. IV and subcutaneous NAD+ have essentially no controlled trial data. The trials that exist are of oral precursors, they reliably raise the biomarker, and they have mostly failed to move clinical endpoints. A course of infusions costs a great deal and delivers, pharmacologically, a set of nicotinamide precursors that oral NR would have delivered for a fraction of the price. If you want the honest version: the strongest argument for IV NAD+ over an oral precursor has never been tested in a controlled trial. Fourth, degradation: NAD+ is less stable than almost any peptide on this list, and a solution that has turned yellow has genuinely degraded and should be discarded rather than used. Fifth, timing — it is stimulating, and dosing late reliably wrecks sleep. Sixth, unsupervised home IV. The reaction is common enough that someone competent should be present, and this is one of the few places on this site where that is a practical safety statement rather than a reflex.

1. 25 mgFirst subcutaneous dose — 25 mg, diluted generously. The point of this step is entirely tolerance — NAD+ solutions are strongly acidic and the burn is the limiting factor, not any systemic effect. Inject slowly and note how the site looks at 24 hours.
2. 50 mgSecond and third doses — 50 mg. If 25 mg was tolerable, this is the standard working dose for most people and many never go beyond it. Increase the dilution volume rather than the injection speed.
3. 100 mgOngoing, if 50 mg is comfortable — 100 mg is the upper end of typical clinic subcutaneous dosing. There is no evidence that 100 mg outperforms 50 mg; the reason to go higher is habit rather than data. Morning dosing throughout — it is stimulating in many people and disrupts sleep if taken late.
4. 250 mgIntravenous, if moving to that route — 250 mg in saline over at least two hours for a first infusion. The rate, not the dose, drives the reaction — start the drip slow and only increase if the first thirty minutes are completely uneventful. Higher doses of 500-1000 mg belong to later sessions once you know how you respond, and always over three to four hours.

• Sirtuins (SIRT1-7) — NAD+ is an obligate co-substrate; sirtuin Km for NAD+ sits within the physiological concentration range, which is why sirtuin activity is genuinely NAD+-sensitive.

  Deacylation of histones and metabolic regulators. This is the axis the entire longevity claim rests on, and it is the one part of the story where NAD+ availability plausibly is rate-limiting.

• PARP1 and PARP2 — NAD+ is the ADP-ribose donor.

  DNA repair. PARP activation after DNA damage consumes NAD+ heavily and competes with sirtuins for the same pool — this is the mechanism by which accumulated damage depletes NAD+.

• CD38 — NAD+ is the substrate; CD38 has a high catalytic efficiency for it.

  The dominant NAD+ consumer in ageing tissue. CD38 expression rises with inflammation, and this is now understood to be the principal driver of age-related NAD+ decline. Practically: CD38 is the reason a drip does not fix the problem.

• Electron transport chain complex I — Redox cofactor, not a binding target.

  Electron entry into the respiratory chain. This pool is tightly buffered and not plausibly limiting in healthy tissue.

• Chronic nicotinamide riboside supplementation in healthy middle-aged and older adults (Martens et al.) Randomised placebo-controlled crossover · n=24 · 6 weeks · 2018

  Safety, tolerability and elevation of NAD+ metabolism at 1000 mg per day of nicotinamide riboside. NR was well tolerated and effectively raised NAD+; suggestive but non-definitive signals on blood pressure and arterial stiffness were flagged for future study. This is the clean demonstration that you can raise the biomarker — and note the endpoint was the biomarker.

• Nicotinamide riboside and the metabolic response to endurance exercise (Stocks et al.) Randomised placebo-controlled crossover · n=8 · 1 weeks · 2021

  Whole-body and skeletal muscle metabolic responses to a single bout of endurance exercise after one week of 1000 mg/day NR. NR did not alter the metabolic response — a clean negative result on a functional endpoint.

Minutes into an infusion: the flushing, chest tightness and restlessness begin, and they track the drip rate rather than the cumulative dose. This is a pharmacological reaction, not a therapeutic effect, and people routinely misread it as one. Two to four hours: the infusion completes; intact plasma NAD+ has a residence time of minutes and is long gone as the intact molecule by the time you leave. Hours to the same evening: many people report a stimulated, alert feeling, which is also the reason late dosing ruins sleep. Days three to five of a loading block: this is where subjective reports of improved energy cluster, and it is indistinguishable from the effect of having spent five days doing something deliberate about your health. Weeks four to twelve: if any biomarker is going to move, this is when. Blood NAD+ will rise; whether anything else does is the unanswered question the entire field is built around.

The most important stacking fact is a negative one: oral NMN or NR feeds the same salvage pathway that injected NAD+ ends up feeding after degradation, so running both is largely paying twice for one effect. If cost matters to you at all, pick a route. The SS-31 pairing is the most mechanistically defensible in this class — cofactor supply plus membrane structure, no overlapping node — and it is completely untested. Resveratrol is the traditional partner on the sirtuin-activation theory, and the resveratrol side of that story has weakened substantially over the past decade; do not treat it as established. The interaction that actually deserves attention is with methyl donors: high-dose chronic NAD+ or precursor use draws on S-adenosylmethionine for clearance via N1-methylnicotinamide, and running it alongside anything else that consumes methyl groups, in someone with marginal B12 or folate status or an MTHFR variant, is where the homocysteine rise shows up. Check it rather than assuming. Finally, the cancer question is not boilerplate here: NAD+ supports the biosynthetic and DNA-repair capacity of proliferating cells, and whether raising it is good or bad in the presence of a malignancy is a genuinely open research question rather than a settled caution.

Against oral NR and NMN: this is the comparison that matters and it is uncomfortable for the injectable market. Oral precursors have randomised human trials, reliably raise blood NAD+, are cheap, and are the only NAD+ intervention with any controlled human data. IV and subcutaneous NAD+ have essentially none. Given that IV NAD+ is degraded extracellularly to precisely the precursor species you would have swallowed, the burden of proof sits squarely on the injectable route and it has not been met. Against SS-31: SS-31 has a label, human pharmacokinetics and phase 3 data; NAD+ has more human trials than most things on this page but they mostly demonstrate biomarker movement without outcome movement. Different failure modes, both worth understanding. Against CD38 inhibition: mechanistically this is arguably the more rational target, since rising CD38 is the main driver of the decline, but no CD38 inhibitor is available to consumers. Against exercise and caloric restriction: both raise NAD+ endogenously and do many other things besides. Against doing nothing, for a healthy adult: the honest answer is that after a decade of trials, nobody has demonstrated that raising NAD+ in a healthy person changes a clinical outcome. The biology of the decline is solid. The intervention is not.

$100–$3000/month. Not verified against live pricing this session, and the range is genuinely this wide because the routes are not comparable products. Self-administered subcutaneous NAD+ from research-grade powder at 50-100 mg several times weekly sits at the bottom end. Clinic IV infusions are commonly priced per session in the several-hundred-dollar range, so a loading block of three to five infusions followed by weekly maintenance reaches the top of this range or beyond it. For context, 1000 mg per day of oral nicotinamide riboside — the dose used in the trials that actually exist — costs a small fraction of any injectable protocol and is the intervention with human trial data behind it.

• ?Intravenous and subcutaneous NAD+ have essentially no controlled human trial data. The 2026 systematic review found one PK pilot with no eligible clinical outcomes.
• ?Subcutaneous NAD+ bioavailability has never been measured.
• ?No published human pharmacokinetic profile for injected NAD+ was resolvable in this session — the widely quoted minutes-long residence time is consistent with the biochemistry but I did not resolve a primary human PK paper.
• ?Whether intravenous NAD+ delivers anything an oral precursor does not has never been tested head to head.
• ?The blood-brain barrier field is set to 'no' for intact NAD+ on the basis that a doubly charged dinucleotide does not cross membranes; whether precursor species derived from it reach the brain is a different and partly separate question.
• ?Volume of distribution, protein binding and clearance figures are unmeasured for administered NAD+.
• ?Time to steady state is not a meaningful concept for a molecule that is degraded within minutes and resynthesised intracellularly, so it is left null rather than estimated.
• ?The methylation/homocysteine concern is mechanistically sound and the threshold given is a general clinical one, not an NAD+-specific validated cutoff.
• ?Whether raising NAD+ is harmful in the presence of occult malignancy is genuinely unresolved rather than merely cautious.
• ?Cost figures are estimates and were not verified against live clinic or vendor pricing.
• ?The titration ladder here reflects clinic and community practice, not a validated dose-escalation schedule — no such schedule has been published.

• Chronic nicotinamide riboside supplementation is well-tolerated and elevates NAD+ in healthy middle-aged and older adults Martens CR, Denman BA, Mazzo MR, Armstrong ML, Reisdorph N, McQueen MB, Chonchol M, Seals DR, Nature Communications, 2018 · PMID 29599478

  The cleanest human demonstration that an oral precursor raises NAD+ safely. Also the clearest illustration of the field's problem: the endpoint achieved was the biomarker, not an outcome.

• Nicotinamide riboside supplementation does not alter whole-body or skeletal muscle metabolic responses to a single bout of endurance exercise Stocks B, Ashcroft SP, Joanisse S, Dansereau LC, Koay YC, Elhassan YS, Lavery GG, Quek LE, O'Sullivan JF, Philp AM, Wallis GA, Philp A, The Journal of Physiology, 2021 · PMID 33492681

  A negative functional result on a real physiological endpoint. Small (n=8) but worth reading precisely because negative NAD+ trials get much less attention than positive biomarker ones.

• NAD+ supplementation for anti-aging and wellness: a PRISMA-guided systematic review of preclinical and clinical evidence Gallagher C, Emmanuel OO, Ageing Research Reviews, 2026 · PMID 41655607

  The current systematic review of the whole field. Notably, it identified only one intravenous NAD+ pharmacokinetic pilot and had to classify it as contextual evidence because it carried no eligible clinical outcomes — that single sentence is the most honest summary of the IV NAD+ evidence base that exists.