NAD+: The Biology, the Evidence, and What the Drip Can Actually Claim

NAD+ is real, important, and genuinely declining as you age. Whether an intravenous infusion of it does anything for you is a separate question with a separate — and much thinner — answer.

⛔ If You Are Here Because You Are Tired, Start Here

Fatigue and brain fog are the commonest reasons people look up NAD+. They are also symptoms with a long differential, several parts of which are common, serious, and treatable — usually with something cheaper than an infusion.

Before spending money on any drip, ask your own doctor for:

⚠️ Fatigue that is new, progressive, or accompanied by weight loss, night sweats, fever or lumps needs prompt medical assessment. Those features are not a reason to buy anything on this page; they are a reason to see a doctor.

We would rather you did that first. If it comes back clear and you still want to talk about cellular optimisation, the rest of this page is written for you.

The Science: What NAD+ Actually Does

A coenzyme with two different jobs

NAD+ (nicotinamide adenine dinucleotide) is a coenzyme present in every cell, derived from vitamin B3. It does two things that are easy to confuse and important to keep separate^1,2:

1. Electron carrier (recycled). NAD+ accepts electrons from nutrient breakdown to become NADH, then donates them to the mitochondrial electron transport chain, regenerating NAD+. This drives ATP production. In this role NAD+ is not consumed — it cycles.

2. Enzyme substrate (consumed). Three enzyme families cleave NAD+ and use it up:

Because this second role destroys NAD+, cells must continuously resynthesise it — mainly through the salvage pathway, whose rate-limiting enzyme is NAMPT.

⚠️ A common misstatement worth correcting: NAD+ consumption does not cause "permanent depletion." Salvage synthesis runs constantly. What changes with age is the balance between consumption and resynthesis.

Why NAD+ declines

Proposed contributors^5,6: rising PARP activity as DNA damage accumulates; increasing CD38 expression with age and inflammation; declining NAMPT activity; and lifestyle factors including poor sleep, excess alcohol, inactivity and metabolic dysfunction.

⚠️ A framing point worth keeping straight. NAD+ metabolism touches several of the widely cited "hallmarks of ageing" — genomic instability, mitochondrial dysfunction, cellular senescence and altered intercellular communication among them²¹. That NAD+ connects to many ageing processes is a statement about biological wiring. It is not evidence that raising NAD+ reverses any of them, and the two are frequently blurred.

How much does it decline? Less precisely than you will read elsewhere

Massudi et al. (2012)⁴ is the study usually cited. What it actually did:

• Human pelvic skin samples, n = 49, ages 15-77 plus newborns
• NAD+ correlated negatively with age: r = −0.706 (p = 0.001) in males; r = −0.537 (p = 0.01) in females
• PARP activity rose with age in males (r = 0.768) and correlated inversely with tissue NAD+ (r = −0.639)
• ⚠️ The associations were "less evident in females"

⚠️ Three things to hold on to. The measurements are from skin, not blood, muscle or brain. They are correlations, not percentages by decade. And the sex difference is real. The neat curves you will see — including versions of the figure above — put a smooth quantitative line through data that was not collected that way. The direction is well supported. The precision is not.

Sirtuins

Sirtuins are seven NAD+-dependent enzymes regulating metabolism, DNA repair, inflammation, circadian rhythm and stress responses^7,8. They cannot function without NAD+ — that dependence is real and well characterised.

⚠️ They are often called "longevity genes." That name comes from lifespan extension in model organisms — yeast, worms, flies and mice. It is not a demonstrated human longevity effect, and we are going to stop using the phrase after this sentence.

The Evidence, Separated by Route and Endpoint

Almost all confusion about NAD+ comes from merging three different questions. Here they are apart.

What the rodent work shows — and it is rodent work

Gomes et al. (2013)⁹ showed that raising NAD+ in aged mice restored mitochondrial function, with 2-year-old mice reaching parameters similar to 6-month-old mice. Zhang et al. (2016)¹⁰ showed NAD+ repletion improved mitochondrial and stem cell function and extended lifespan in mice. Yoshino et al. (2011)¹¹ showed NMN treated the pathophysiology of diet- and age-induced diabetes in mice. Diguet et al. (2018)¹² showed NR preserved cardiac function in a mouse model of dilated cardiomyopathy.

⚠️ These are the studies that made the field exciting, and they are all rodent studies. The 2026 systematic review found that across 80 rodent studies, NAD+ augmentation was "frequently associated with improvements" — and that this has not carried across to human functional outcomes¹⁶.

The human oral-precursor trials

Martens et al. (2018)¹³ — randomised, double-blind, placebo-controlled crossover, healthy middle-aged and older adults, NR 1000 mg/day for 6 weeks. NR was well tolerated and effectively stimulated NAD+ metabolism. On function, the authors were careful: their results "suggest that future clinical trials should further assess the potential benefits of NR for reducing blood pressure and arterial stiffness." ⚠️ That is a signal worth following up, not a demonstrated effect.

Dollerup et al. (2018)¹⁴ — randomised, double-blind, placebo-controlled, 40 obese insulin-resistant men, NR 2000 mg/day for 12 weeks, with hyperinsulinaemic euglycaemic clamp, indirect calorimetry, DXA and MR spectroscopy:

⛔ "Insulin sensitivity, endogenous glucose production, and glucose disposal and oxidation were not improved by NR supplementation. Similarly, NR supplementation had no effect on resting energy expenditure, lipolysis, oxidation of lipids, or body composition."

Safety was fine; efficacy was null. We are quoting it because it is one of the best-designed trials in the field and it is negative.

Elhassan et al. (2019)¹⁵ — randomised, double-blind, placebo-controlled crossover, 12 aged men, NR 1 g/day for 21 days. NR did elevate the skeletal muscle NAD+ metabolome ⭐ and did depress circulating inflammatory cytokines ⭐. But muscle RNA sequencing showed downregulation of energy metabolism and mitochondrial pathways "without altering mitochondrial bioenergetics."

The current synthesis

Gallagher et al. (2026)¹⁶ — PRISMA-guided systematic review, 113 studies (33 human intervention studies, 28 randomised; 80 rodent studies), January 2010 to October 2025, covering oral and parenteral administration:

• Rodent studies: frequent improvements across metabolic, mitochondrial, inflammatory and functional outcomes
• Humans, oral NR and NMN: consistent biochemical target engagement, generally well tolerated
• Humans, functional outcomes: "heterogeneous and often null or endpoint-specific"
• ⛔ "No eligible outcomes trials evaluated intravenous or intramuscular NAD⁺ itself for anti-aging or wellness indications." An IV NAD+ pharmacokinetic pilot was identified as contextual evidence only

Prokopidis et al. (2025)¹⁷ — meta-analysis of randomised trials in older adults. NMN showed no significant effect on skeletal muscle index (MD −0.42, 95% CI −0.99 to 0.14), handgrip strength (MD 0.61, −0.89 to 2.10), gait speed (MD −0.01, −0.08 to 0.06) or five-time chair-stand (MD −0.21, −0.70 to 0.29).

⚖️ The one randomised IV NAD+ trial

Yu et al. (2026)¹⁸ — single-centre, prospective, randomised, placebo-controlled, 180 adults with heart failure from ischaemic cardiomyopathy (LVEF ≤ 45%, NYHA II-III), intravenous NAD+ 10 mg/day vs placebo for 7 days on top of guideline-directed therapy:

⭐ This is a genuine randomised trial of intravenous NAD+ with a met primary endpoint, and it should be on the table.

⚠️ Three limits on reading it across to wellness use. It studied people with heart failure, not healthy adults. Every secondary endpoint was a non-significant trend. And the dose was 10 mg/day — 70 mg over the whole course. Wellness protocols, ours included, give 500-1000 mg in one sitting. We cannot tell you that a dose 50 to 100 times larger, in a different population, for a different purpose, produces a benefit. Nobody has tested it.

Routes of Administration

⚠️ On "100% bioavailability." For anything given intravenously, bioavailability is 100% by definition — it is a statement about reaching the bloodstream, not about reaching the inside of a cell. Intact NAD+ is largely broken down extracellularly before cellular uptake, which is why the field studies precursors rather than the intact molecule³. "100% bioavailable" is true and does not mean what it is usually used to mean.

What an Infusion Involves

The procedure. IV NAD+ is given slowly, typically over 2-4 hours. The slow rate is not optional — it is how the infusion reactions are controlled.

Infusion reactions are common and rate-dependent:

• Flushing and warmth
• Chest tightness — the most-reported and most alarming to patients
• Nausea
• Headache
• Transient increase in heart rate

These typically settle when the rate is reduced and resolve at the end of the infusion. They are expected rather than unusual, and you should be told about them before you consent, not during.

Cautions:

• Pregnancy — insufficient data
• Cardiac conditions and rhythm-affecting medications — individual evaluation needed
• Active cancer — NAD+ supports cell proliferation, and the effect of raising it in the presence of malignancy is not established. We treat this as a reason to decline, not a footnote

⚠️ We are not going to tell you the effects are "not dangerous." They are usually mild and manageable; the honest statement is that serious events are not described in the small published literature, and that literature is small.

NAD+ and Stem Cell Therapy: What We Can and Cannot Say

Our protocol places NAD+ on Day 1, before MSC administration on Day 2. You are entitled to know why, and to know what that reasoning rests on.

The reasoning is mechanistic. MSCs act largely through paracrine signalling, and responding to those signals requires cellular energy, functional mitochondria and intact repair machinery — all NAD+-dependent. If NAD+ is depleted, the argument goes, the recipient tissue responds less well.

⛔ The reasoning has not been tested in humans. There is no trial comparing MSC therapy with NAD+ preparation against MSC therapy without it — not for any indication, not at any dose, not by any route. We have searched for it repeatedly and it does not exist.

So the honest position is: the sequencing is biologically plausible and commercially convenient, and those two facts are not evidence. If you are choosing between packages on the basis that NAD+ will make the stem cells work better, you should know that claim is unsupported, and we would rather tell you than let you infer it.

⚠️ A related finding from the MSC literature worth your attention. In a randomised dose-finding trial of allogeneic MSCs in ageing frailty (n = 30), physical performance improved in the 100-million-cell group — 6-minute walk, short physical performance battery, FEV1 all improved (p = .01) — and not in the 200-million-cell group or placebo¹⁹. More cells were not better. That is one small trial and should not be over-read, but it argues against assuming that bigger packages produce bigger effects.

Where NAD+ Research Is Genuinely Interesting

Reported honestly: this is an active field and some of it may well pan out. What is currently under investigation, mostly in early-phase human trials or rodent models:

• Neurodegeneration — NAD+ metabolism is altered in Alzheimer's and Parkinson's disease models²⁰; human outcome data is not yet available
• Cardiovascular disease — the heart failure trial above¹⁸, plus rodent cardioprotection¹²
• Metabolic health — mechanistically central; the human trials to date have been null on insulin sensitivity¹⁴
• Inflammation — NR reduced circulating inflammatory cytokines in aged men¹⁵, one of the more reproducible human findings

⚠️ None of this establishes that an infusion will make you feel better, think more clearly, or age more slowly. Those are the claims most often made and the ones with least support.

Frequently Asked Questions

Does NAD+ decline with age?

Yes — the direction is well supported in human tissue⁴. The specific percentages quoted in marketing (including "50% by 60") are not traceable to a measured dataset we could find, and the best human study measured skin, reported correlations rather than percentages, and found weaker associations in women.

Will an IV NAD+ drip give me more energy?

We cannot tell you that it will. No outcomes trial has evaluated intravenous NAD+ for wellness or anti-ageing indications¹⁶. Many people report feeling better afterwards; that is not the same as evidence, and infusions are a setting in which people commonly feel better regardless of what is in the bag.

Are oral supplements as good?

For raising NAD+ metabolites, oral NR and NMN are the better-evidenced option — that effect is established in randomised trials^13,15. Whether raising the biomarker helps you is the unanswered question for both routes^16,17.

Does NAD+ make stem cell therapy work better?

There is no human evidence that it does. The mechanistic argument is reasonable; it has never been tested.

Why is chest tightness so commonly reported?

It is a rate-dependent infusion reaction and the main reason NAD+ is given over hours rather than minutes. It is not usually dangerous, but it should be explained beforehand.

Can NAD+ help my fatigue and brain fog?

Possibly, and possibly not — but that is the wrong first question. The first question is why you are tired. Anaemia, thyroid disease, sleep apnoea, diabetes, B12 deficiency, depression and medication effects are all common, all testable and all treatable. Please get those excluded first, by your own doctor.

Is NAD+ safe with my medications?

Disclose your full medication list. Drugs affecting heart rhythm and certain cardiac conditions require specific evaluation. Active cancer is a reason to decline.

Is this anti-ageing?

NAD+ biology is one of the more credible strands in ageing research, and it is being seriously investigated. Nothing currently published shows that raising NAD+ in humans slows ageing. Anyone telling you otherwise is ahead of the data.

Take the Next Step

If you are tired: see your own doctor first. A full blood count, TSH, HbA1c, B12 and an honest conversation about sleep will cost you very little and may find something an infusion cannot fix.

If that is done and you want to discuss cellular optimisation:

→ Take Our 2-Minute Cellular Health Assessment

→ Schedule a Discovery Call

We will tell you what the evidence supports and where it stops — including, on this subject, that it stops earlier than most of the market admits.