What NAD+ is
Nicotinamide adenine dinucleotide is a coenzyme present in every cell, central to the reactions that convert food into usable energy. It is also a substrate for enzymes involved in DNA repair and cellular stress responses, including the sirtuins and PARPs.
None of this is controversial. NAD+ is genuinely fundamental, and there is a large, legitimate research field studying its decline with age.
Where the argument actually is
The NAD+ field involves three separate questions that marketing routinely merges into one:
- Is NAD+ important? Yes, unambiguously.
- Does NAD+ decline with age? Broadly yes, with variation by tissue.
- Does raising it produce clinical benefit? This is the question, and it is not settled.
Almost every NAD+ product is sold on the strength of answers one and two, while the purchase decision depends entirely on answer three.
Precursors versus direct administration
Most rigorous human research has used oral precursors — nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN) — rather than NAD+ itself. This is for a good biochemical reason: NAD+ is a large, charged molecule that does not readily cross cell membranes intact.
Those precursor trials have reasonably consistently shown that supplementation raises blood NAD+ levels. What they have generally not shown is convincing improvement in the functional outcomes people care about: physical performance, cognition, insulin sensitivity, or markers of ageing.
Raising a biomarker is not a clinical outcome. A trial showing that NAD+ levels went up has demonstrated that the supplement was absorbed. It has not demonstrated that anything got better.
The IV and injectable question
IV NAD+ infusion is heavily marketed by clinics for fatigue, cognitive function, addiction recovery and anti-ageing. It is also the format with the least controlled evidence of any in this field.
Controlled trials of intravenous NAD+ with clinical endpoints are scarce. Most of what supports the practice is clinic testimonial and open-label observation, both of which are highly susceptible to placebo effects — particularly for subjective endpoints like energy and mental clarity, and particularly when the intervention involves an hour in a clinic attached to a drip.
There is also basic pharmacokinetic uncertainty. Infused NAD+ appears to be substantially metabolised before reaching cells, which raises the question of whether IV administration delivers anything the cheaper oral precursors do not.
Reported effects
IV NAD+ infusion is commonly associated with unpleasant sensations during administration — chest tightness, nausea, flushing, abdominal cramping — which is why infusion rates are typically slowed. These are not usually described as dangerous, but they are notable and consistent.
Longer-term safety of repeated high-dose NAD+ administration is not well characterised.
Regulatory position
NAD+ is not licensed as a medicine for injection or infusion in the UK for any indication. Clinics offering IV NAD+ are not providing a licensed treatment.
Oral precursors such as NR and NMN are sold as food supplements in some markets, which is a different regulatory category with different rules and no requirement to demonstrate clinical efficacy.
Where this leaves you
NAD+ biology is real and worth following. The specific proposition that paying for an infusion of it will make you feel better or age more slowly rests on a thin, largely uncontrolled evidence base, in the format least supported by the research.