NAD+ (and NMN / NR)

NAD+ is a coenzyme every cell depends on, both as an electron carrier and as a consumable substrate for sirtuins and PARPs. Levels fall with age, and precursors like NMN and NR reliably raise them in humans. What has not been shown is that raising the number changes how you age — and that gap between a biomarker and an outcome is the whole argument.

What NAD+ is

NAD+ (nicotinamide adenine dinucleotide) is a coenzyme present in every living cell. It is not a hormone, a peptide or a drug — it is core metabolic machinery, as fundamental as ATP. It does two structurally different jobs, and the difference between them is the key to everything else on this page.

As a redox carrier, NAD+ accepts a pair of electrons to become NADH, delivers them to the electron transport chain in the mitochondria, and returns to its oxidised form. In this role NAD+ is recycled, not consumed. The pool turns over constantly but is not depleted by the work.

As a substrate, NAD+ is cleaved and destroyed. Enzymes including sirtuins, PARPs and CD38 do not merely borrow NAD+ — they break it apart to carry out their reactions, releasing nicotinamide as a by-product. Every time a sirtuin deacetylates a protein, or a PARP responds to a strand break in DNA, a molecule of NAD+ is spent. This is why cells must continuously resynthesise it, and why demand can outstrip supply.

Because NAD+ is central to both energy production and cellular maintenance, and because its levels are widely reported to decline with age, it has become the anchor compound of the longevity supplement industry. NAD+ itself is poorly absorbed when swallowed, so most products supply a precursor the body converts into NAD+ — NMN (nicotinamide mononucleotide), NR (nicotinamide riboside), or a form of vitamin B3. Some clinics also offer NAD+ directly as an intravenous infusion.

How it works

The theory is simple to state: NAD+-dependent maintenance systems slow down as NAD+ falls, so restoring the pool should restore the systems. Each step in that chain is worth examining.

The consumer enzymes are the interesting part. Sirtuins regulate aspects of metabolism, mitochondrial function and stress responses. PARPs detect and help repair DNA damage. CD38 also degrades NAD+, and its activity appears to rise with age and chronic inflammation — so the pool comes under pressure from two directions at once, synthesis becoming less efficient while consumption rises.

Cells make NAD+ by three routes. The salvage pathway recycles nicotinamide back into NMN and then into NAD+, and does most of the day-to-day work. The Preiss-Handler pathway starts from nicotinic acid — plain niacin. The de novo pathway builds NAD+ from tryptophan. Every oral precursor product is feeding one of these existing routes rather than doing anything novel.

This is where the precursor choice matters. NR is transported into cells and phosphorylated to NMN, which is then converted to NAD+. NMN is one step further along the pathway, which is often marketed as an advantage — but being closer to the destination on a whiteboard does not mean more of it arrives. There is genuine, unresolved debate about whether orally administered NMN is largely dephosphorylated back to NR in the gut before absorption, which would make that advantage illusory. Niacin raises NAD+ effectively but causes the well-known flushing reaction in many people. These are not interchangeable products, and the marketing rarely acknowledges it.

IV NAD+ deserves particular scrutiny. The pitch is that infusing NAD+ directly bypasses absorption problems. The mechanistic question that raises is whether an intact NAD+ molecule — large, charged and highly polar — crosses cell membranes in meaningful quantities, or whether it is broken down in the bloodstream to smaller fragments then taken up as ordinary precursors. If it is the latter, an infusion is an expensive and uncomfortable route to the same place a tablet reaches. That is a fair question to put to any clinic offering it, and one a clinic should be able to engage with.

What the human evidence actually shows

Precursors raise NAD+ levels in humans. This part is real. Trials of oral NR and NMN have repeatedly shown measurable increases in blood NAD+, and it is among the better-replicated findings in the supplement space.

They have been generally well tolerated in the periods studied — typically weeks to a few months.

Functional results are mixed, small and short. Some trials in older adults report modest signals: one 2024 study described maintained walking speed and improved self-reported sleep quality. Others found little or nothing on their chosen measures. The trials are small, the outcomes measured differ between studies, and follow-up is short — a pattern that historically resolves toward a smaller effect than hoped rather than a larger one.

The critical gap is between the biomarker and the outcome. Raising a blood NAD+ level is not the same achievement as improving health, function or lifespan. NAD+ is a surrogate marker, and the history of medicine is full of surrogate markers that moved beautifully while the outcomes that mattered did not follow. There is at present no robust human evidence that raising NAD+ slows ageing, extends lifespan or prevents age-related disease. Much of the enthusiasm traces to mouse work, and mice are not a reliable guide to human ageing.

IV NAD+ has the thinnest evidence of all. Despite being the most heavily commercialised form, it has very little controlled-trial data behind what it is marketed for — fatigue, brain fog, "cellular reset", recovery, addiction. The infusion industry is substantial and growing; the outcome evidence supporting it is not. That mismatch is worth naming plainly rather than sneering at: the underlying biology is real, the clinics are often staffed by well-intentioned people, and the specific claim that an infusion produces durable health benefits remains unproven.

Our longer piece on NAD+ evidence versus marketing works through the commercial side of this in more detail.

Regulatory positions and trial results in this area have moved more than once in recent years. Anything you read about NAD+ or NMN status — including here — is worth confirming against current sources with a registered pharmacist or doctor.

Regulatory status in Australia

The position on NMN changed recently, and it is specific. Following an amendment to the TGA's Permissible Ingredients Determination that took effect in December 2025, NMN became usable as an ingredient in Listed medicines (AUST L), subject to conditions attached to the determination — restriction to adults, a specified maximum daily amount, and exclusion in pregnancy and breastfeeding. Listed medicines are not individually assessed for efficacy by the TGA; they are drawn from a pre-approved ingredient list and the sponsor certifies compliance. That is a meaningful change from the previous position, but it is not TGA endorsement that NMN works.

NAD+, NAD and NADH as oral ingredients have not been permitted on the same basis. Status can shift — a registered pharmacist can confirm whether a specific product is compliant.

Compounded NAD+ for injection or infusion is a different pathway again, supplied on prescription for an individual patient. Compounding is lawful and long-established, but it is not registration: the preparation has not been evaluated by the TGA, there is no TGA-approved Product Information, and batch consistency depends on the pharmacy's own systems. Our explainer on compounded versus TGA-registered medicines covers what that means in practice.

Advertising prescription-only medicines directly to consumers is restricted in Australia. A practitioner can discuss options with you in a consultation; public promotion of a prescription compound with claimed benefits is a different thing, and a reasonable signal to weigh when assessing a clinic.

Who it is being studied for — and who it is not for

Formal research interest centres on age-related metabolic decline, mitochondrial dysfunction, certain neurodegenerative and neuromuscular conditions, and cardiometabolic health. Most of it is early-stage. The uses most commonly sold — fatigue, brain fog, jet lag, hangover recovery, "cellular optimisation", general anti-ageing — sit well ahead of that evidence, as extrapolations from mechanism rather than conclusions from trials.

A practitioner would be particularly cautious, or would decline, in pregnancy and breastfeeding, in active malignancy, in significant kidney or liver impairment, and where an undiagnosed cause of symptoms has not yet been investigated.

That last point carries real weight. Fatigue and poor concentration have a long list of common, treatable causes — iron deficiency, thyroid dysfunction, sleep apnoea, depression, poorly controlled diabetes, medication effects, alcohol. A credible practitioner investigates those first. If a clinic proposes an infusion before anyone has looked at your bloods, that tells you what kind of clinic it is.

Risks and considerations

Oral NMN and NR have been well tolerated in the trials conducted, but long-term safety data in healthy people are limited because the studies have been short. Product quality in the supplement market varies widely, and independent testing of precursor products has repeatedly found content that does not match the label.

Infusions add a separate risk category. Any intravenous therapy carries the possibility of infection, phlebitis, extravasation and infusion reactions. Reported effects during NAD+ infusion include nausea, chest tightness, flushing, cramping and headache — which is why clinics administer it slowly. A cannula placed without a practitioner able to manage a reaction is a meaningful hazard.

A theoretical concern worth understanding. NAD+ availability supports cell proliferation, and inhibiting NAD+ synthesis has been explored as an anti-cancer strategy. Whether deliberately raising NAD+ could favour the growth of existing abnormal cells is unresolved. It is not a demonstrated harm and should not be presented as one — but it is exactly the sort of open question that argues for a doctor's involvement rather than a self-directed purchase.

And cost is a real consideration: infusion programmes are expensive, often sold in packages, and the evidence does not justify treating that spend as an investment in longevity.

What to ask a doctor

• What are you actually treating, and how was that assessment reached?
• Have the common causes of my symptoms been investigated and excluded first?
• Is there human evidence that this helps my goal — outcomes, not mechanism?
• Which form are you recommending, and why that one over the alternatives?
• For an infusion: what is the evidence that infused NAD+ enters cells intact rather than being broken down first?
• Is this product registered, listed or compounded? If compounded, which pharmacy makes it and under what quality assurance?
• What would tell us this is working, and by when? What is the stopping rule if it isn't?
• How does this interact with my current medicines and conditions, and what does the full course cost?

FAQ

Is NMN legal as a supplement in Australia? Its status changed in December 2025, when NMN became permissible in Listed medicines under conditions set in the TGA's Permissible Ingredients Determination. Regulatory positions move — a registered pharmacist can confirm whether a particular product complies today.

Is raising NAD+ proven to slow ageing? No. Precursors reliably raise measurable NAD+ levels. Robust human evidence that this slows ageing, extends lifespan or prevents age-related disease does not currently exist. That distinction is the single most useful thing to carry away from this page.

Are NMN, NR and IV NAD+ interchangeable? No. They differ in the biochemical step they enter at, in absorption, in evidence quality, in cost and in regulatory status. Treating them as one product is a marketing convenience, not a biological fact.

Is NAD+ the same as SS-31 or MOTS-c? No, though all three appear in the same mitochondrial conversation. SS-31 is a synthetic peptide that binds cardiolipin to stabilise the structure of the inner mitochondrial membrane. MOTS-c is a peptide encoded in the mitochondrial genome, studied as a metabolic signalling molecule. NAD+ is a coenzyme and consumable substrate that thousands of enzymes depend on. They act at completely different levels, with very different evidence bases and regulatory positions. Sharing a subject heading does not make them substitutes for one another.

Does NAD+ help hangovers, jet lag or brain fog? These are the highest-volume marketing claims and the lowest-evidence ones. There is no good controlled human trial support for them.

Should I look for a clinic that offers it? Start with the problem, not the compound. Find a practitioner who will investigate why you feel the way you do and tell you honestly where the evidence stops. If something in this category is genuinely appropriate afterwards, it will still be there — and you will be better placed to judge whether it is worth your money. Our guide on choosing a clinic and the doctor-supervised longevity clinics listing are useful starting points.