NAD+ and Longevity

What is NAD+?

NAD+ (nicotinamide adenine dinucleotide) is a coenzyme present in every cell, where it carries electrons through the reactions that produce usable energy and acts as a substrate for enzymes involved in DNA repair and gene expression. That much is textbook biochemistry rather than a wellness claim, and it is the entire basis for the interest in it. What NAD+ is not is a youth molecule — the distance between a real mechanism and a measurable benefit in people is where almost all of the marketing lives.

NAD+ explained

Does NAD+ decline with age?

Several human studies do find lower NAD+ in older tissue, particularly skin and muscle, and the direction is consistent enough to take seriously. The claim is repeated with far more confidence than the data supports, though: NAD+ is unstable and genuinely hard to measure, levels differ between blood, muscle, skin and liver, and most human studies are small and compare younger people with older people at a single moment rather than following the same people as they age. There is no established normal range for NAD+, and your own tissue level cannot be inferred from your age.

NAD+ and longevity guide

Can I get my NAD+ level tested?

No NAD+ test is in routine clinical use, and no commercially available NAD+ test should be used to drive a treatment decision. The molecule starts degrading as soon as a sample is taken, different laboratory methods produce different answers, and there is no reference range to compare a result against. If the real question is why you feel flat, a baseline panel covering thyroid, iron, B12, glucose and hormones answers far more than any NAD+ measurement on the market.

Lab testing

What is the difference between niacin, NR and NMN?

Niacin (vitamin B3), nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN) are all NAD+ precursors — molecules the body converts into NAD+ — differing mainly in how many steps from NAD+ they sit and in how they are regulated and priced. Precursors exist because cells do not readily take up whole NAD+ from the bloodstream; extracellular NAD+ is largely taken apart at the cell surface and rebuilt inside. Niacin is old, cheap and unpatentable; NR and NMN are newer, proprietary and expensive, which is a large part of why you have heard of them and not of niacin.

Niacin, NR, NMN and NAD+

Do NAD+ precursors actually raise NAD+?

Yes — randomized, placebo-controlled human trials show that oral NR and NMN reliably raise measured NAD+ in blood, and the rise tracks with how much is taken. That finding is solid and reproducible. What has not reliably followed is a clinical benefit: trials looking at insulin sensitivity, muscle strength and function, walking distance, fatigue, blood pressure and cognition have produced mixed results, usually small, in short studies with few participants, and a signal found in one trial often fails to reappear in the next. Raising the number is established; turning that into something you can feel, or a clinician can measure on you, is the step that has not been made.

NAD+ and longevity guide

Does NAD+ slow aging?

No human trial shows that NAD+ therapy slows aging, and anyone telling you otherwise is ahead of the evidence. The mechanism is well described and the research interest is genuine, but what the trials demonstrate is that precursors raise measured NAD+ in blood — not that doing so changes how a person ages. ACT 2 Health does not describe NAD+, or anything else it offers, as anti-aging, because that claim has not been earned.

NAD+ and longevity guide

Is a NAD+ injection better than an oral NAD+ supplement?

It is genuinely unsettled, and nobody can honestly tell you otherwise. Injecting bypasses digestion and briefly produces a far higher blood level than any oral route, which is a real pharmacokinetic difference rather than a marketing one. But circulating NAD+ is broken down quickly and enters cells largely as smaller pieces — roughly what an oral precursor supplies more slowly and more cheaply. Almost all of the human trial evidence was generated with oral precursors, and no good study has compared injected NAD+ with an oral precursor head-to-head on any outcome a patient would care about.

Injection or supplement

Is NAD+ FDA-approved?

No. NAD+ injections are compounded preparations and are not FDA-approved for any use — they are not reviewed by the FDA for safety or effectiveness, and they are not equivalent to or interchangeable with any branded product. A licensed clinician may still judge one appropriate for an individual patient, but that is a clinical decision, not a regulatory finding of effectiveness. Any marketing that calls NAD+ therapy FDA-approved is simply wrong.

Is NAD+ FDA-approved?

Is NMN legal to buy in the United States?

NMN sits in a contested position rather than a settled one: in 2022 the FDA took the view that NMN is excluded from the statutory definition of a dietary supplement, on the basis that it had already been authorized for investigation as a new drug. The practical result is a compound still sold widely online whose standing as a supplement is disputed. NR is not in that position, and niacin is a recognized vitamin that has never been in question. None of this says anything about whether NMN works — regulatory status and efficacy are different questions.

Is NAD+ FDA-approved?

How long before I would notice anything from NAD+ therapy?

There is no reliable timeline for NAD+ therapy, because there is no established effect to put a timeline on. People who report a change usually describe it within days to a few weeks, and those reports are not the same thing as evidence. The defensible way to approach it is a trial with a defined endpoint and a date to review it — including the honest conclusion that nothing changed — rather than a subscription that renews while nobody is looking.

How quickly NAD+ works

Why do people say they feel great after a NAD+ infusion?

Because they usually do feel better, and because the setting is close to a perfect placebo environment: real expense, a trip, an hour of clinical attention, and a decision made in advance that this would help. Placebo responses are largest for exactly the outcomes this category sells — energy, mood, focus, general well-being — and they scale with price and ritual. People also tend to start at a low point, and low points drift back toward a person's own average without any help, and few people start an infusion in isolation rather than alongside better sleep or new training. Personal testimony cannot separate the compound from the circumstances; only a controlled trial can, and for injected NAD+ that trial has not been done.

NAD+ and longevity guide

Are there side effects from NAD+ injections?

The commonly reported effects of NAD+ are flushing, nausea, cramping, chest tightness and a sensation of pressure during or shortly after administration, and they are closely tied to how fast it is given — slower administration generally means less of it. Injection-site soreness, redness and bruising also occur. The long-term safety of injected NAD+ has not been established in controlled human studies, which is a different and more honest statement than saying it is safe.

NAD+ side effects

Does NAD+ interact with medications?

NAD+ has no well-characterized interaction profile, which is itself the reason to disclose everything you take before starting it. Tell your clinician about all prescription medications, over-the-counter drugs and supplements — niacin taken alongside a statin, anything affecting the liver, and blood thinners all matter. Anyone in active cancer treatment should raise NAD+ with their oncologist before starting, because the enzymes that consume NAD+ are involved in DNA repair and that question belongs to the team managing the cancer.

NAD+ and other medications

Who is a good candidate for NAD+ therapy?

A reasonable NAD+ candidate is an adult whose fundamentals are already in place — sleep, resistance training, protein, cardiovascular risk addressed — who has had the common causes of fatigue ruled out on a blood panel, and who wants to try the category understanding that the case for it is mechanistic rather than clinical. Anyone whose thyroid, iron, B12, glucose, hormones or sleep apnea has not yet been checked is not a candidate, because several of those have far better answers than an infusion. Curiosity is a legitimate reason to try it; the expectation of a specific result is not.

Who NAD+ suits

Who should avoid NAD+ therapy?

NAD+ therapy is not appropriate during pregnancy or breastfeeding, or for anyone with a known sensitivity to the preparation, and anyone with active cancer, significant liver or kidney disease, or an unstable medical condition should not start it without the clinician managing that condition involved in the decision. It is also the wrong move for anyone whose fatigue has not been investigated yet. A licensed clinician makes this judgment individually, and completing an assessment does not mean a prescription follows.

NAD+ therapy

Does NAD+ help with brain fog?

No human trial shows that NAD+ improves brain fog, memory or concentration. Small studies have measured NAD+ in the brain and in cerebrospinal fluid after precursors are taken, which tells you something crossed — not that thinking improved. Brain fog after 45 has a long list of testable causes, including poor sleep and undiagnosed sleep apnea, thyroid disease, anemia, B12 deficiency, perimenopause, depression, alcohol and medication effects, and working through those is a better first move than an infusion.

NAD+ and cognition

Can I raise NAD+ without an injection?

Yes — the oral precursors niacin, NR and NMN reliably raise measured NAD+, and that is the route most of the human research actually used. Exercise, adequate sleep and limiting alcohol act on the same system and cost nothing. The catch is identical in every case: raising the level is well demonstrated, and what raising it does for you is not.

Raising NAD+ naturally

Do B12 injections give you energy?

B12 injections correct a B12 deficiency, and where a deficiency was genuinely causing the fatigue, treating it can make a real difference. Giving B12 to someone whose level is comfortably normal does nothing — there is no energy benefit in topping up a replete person, whatever a drip-bar menu implies. Which is why the answer to whether you should be getting B12 shots starts with a blood test rather than with a booking.

B12 injection

Who is at risk of B12 deficiency after 45?

B12 deficiency becomes more common with age and clusters in identifiable groups: people taking metformin or long-term acid-suppressing medication, people with reduced stomach acid, vegetarians and vegans, anyone who has had surgery affecting the stomach or ileum, people with pernicious anemia, celiac disease or Crohn's disease, and anyone with repeated nitrous oxide exposure. Left untreated it produces anemia and a neurological picture — numbness, tingling, unsteadiness, memory change — that is not always fully reversible once established. It is measurable on a straightforward blood test, which is what makes it worth checking rather than guessing at.

B12 absorption groups

Do I need B12 injections, or will tablets work?

The route depends on why you are low. Where the problem is intake — a diet with little or no animal protein — oral B12 generally works well. Where the problem is absorption, as in pernicious anemia or after surgery affecting the stomach or ileum, injections bypass the step that is broken, although oral treatment also works for some people through a second, passive absorption route that does not depend on intrinsic factor. Neurological symptoms are usually treated by injection to begin with, and that decision belongs with a clinician who has seen your results.

Tablets or injections

Does injected glutathione do anything?

Glutathione is the body's principal intracellular antioxidant, and whether giving it from outside changes anything in a healthy adult is a far weaker case than the marketing suggests. Injected glutathione does reach the bloodstream, unlike the swallowed form, which is largely dismantled in digestion into its component amino acids — but the human outcome evidence is sparse, and much of what exists concerns skin pigmentation rather than energy, recovery or detoxification. Glutathione injections are compounded and are not FDA-approved, and there is no good human trial evidence that an injection delivers an antioxidant or detoxification benefit for an adult in midlife.

Glutathione injection

Is rapamycin approved for longevity?

No. Rapamycin (sirolimus) is FDA-approved to prevent organ transplant rejection and to treat lymphangioleiomyomatosis — not for aging, longevity or healthspan. Prescribing it for longevity is off-label use, which is legal and common in medicine but means the approval behind the drug says nothing whatever about that use. Rapamycin is a genuine immunosuppressant with real risks, and it belongs only under close clinical supervision with monitoring and lab follow-up.

Rapamycin

Does rapamycin extend lifespan in humans?

No completed human trial shows that rapamycin extends lifespan or healthspan in people. The interest comes from animal work, where rapamycin lengthens life in laboratory mice more consistently than any other compound tested, and from the fact that it acts on mTOR, a pathway central to aging biology. Whether any of that transfers to humans is unknown: the human studies so far have been small and short and have measured markers rather than outcomes, and the intermittent schedules used in longevity practice are not the ones transplant medicine uses.

Sirolimus and rapamycin

What does DHEA do, and is pregnenolone worth taking?

DHEA is an adrenal hormone the body converts into testosterone and estrogen, it declines with age, and it is measurable on a blood test — but the human trial evidence for supplementing it is narrow, with the clearest signals in specific clinical situations rather than in generally healthy adults. Pregnenolone sits a step further back in the same pathway and has substantially less human evidence behind it; most of what is claimed for pregnenolone is claim rather than trial result. Both are hormones rather than vitamins, and both are worth measuring and discussing with a clinician before being taken, rather than bought because they appear on a longevity menu.

What DHEA does

What actually has the strongest evidence for healthspan?

Sleep — including finding out whether you have undiagnosed sleep apnea — resistance training, enough protein to support that training, managing cardiovascular risk through blood pressure, ApoB, Lp(a), glucose and insulin, and not smoking. Every one of those is supported by human evidence of a quality nothing injectable in the longevity category comes close to matching, and several of them are free. If those fundamentals are not in place, no infusion makes up the difference and the money is better spent almost anywhere else. If they are in place and NAD+ still interests you, that is a perfectly reasonable position to hold — it is simply a different one from where most people start.

NAD+ and longevity guide

Results vary. Clinical trial results apply only to the FDA-approved branded medication specifically identified and do not apply to compounded medications. All medications must be prescribed by a licensed provider based on medical necessity.