NAD+What the studies show

Q: What kind of evidence exists for NAD+ (nicotinamide adenine dinucleotide)?

Small human studies. Direct human measurements that NAD+ falls with age, a single 11-person infusion pilot of NAD+ itself, and small trials of oral precursors that raise blood NAD+ without clear clinical change; no outcomes trial of any of it.

The coenzyme every cell uses to move electrons, which falls with age in human skin and brain. Most of the human trials gave a precursor, not NAD+ itself.

6 min read · Small human studies · Updated November 2026

In short

Name: NAD+ (nicotinamide adenine dinucleotide) (sold by Progression Labs as NAD+)
Evidence: Small human studies
Bottom line: Direct human measurements that NAD+ falls with age, a single 11-person infusion pilot of NAD+ itself, and small trials of oral precursors that raise blood NAD+ without clear clinical change; no outcomes trial of any of it.

Before you read this

This guide explains what published studies found. That is all it is.

It is not medical advice and it is not instructions for using anything. Where a dose appears, we are reporting what a named study gave the people or animals in it — a fact about the study, not an instruction to you.

The compounds here are not approved by the FDA for use in people and are sold for laboratory research only. A study tells you what happened to the subjects in it; it does not tell you what would happen to you. Talk to a doctor first.

What it is

Nicotinamide adenine dinucleotide is not a peptide and not a drug in origin; it is a coenzyme that every living cell makes and uses. In its oxidised form, NAD+, it accepts electrons from the breakdown of food, becomes NADH, and hands those electrons to the mitochondria to make ATP — a cycle that turns over many times a second. It is also consumed outright by three families of enzymes: the sirtuins, which regulate gene activity and metabolism; the PARPs, which repair DNA; and CD38, an enzyme on immune cells that breaks down NAD+ and whose activity rises with age ¹. Cells rebuild it from vitamin B3 in its various forms — nicotinamide, nicotinic acid, nicotinamide riboside — and from NMN, the last step before NAD+ itself.

The studies below call this molecule NAD+ (nicotinamide adenine dinucleotide). Progression Labs sells it as NAD+; the guide uses the store's name and the papers use theirs.

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The decline with age

The claim that NAD+ falls with age rests on a few direct human measurements. A 2012 study measured NAD+ in skin samples from 49 people ranging from newborns to 77-year-olds and found levels fell with age, alongside rising markers of oxidative damage ². A 2015 study used magnetic resonance spectroscopy to measure NAD+ non-invasively in the living brain of healthy volunteers and found both total NAD and the NAD+/NADH ratio lower in older adults than in young ones ³. In mice, much of the fall traces to CD38, whose activity rises with age; mice lacking the enzyme keep their NAD+ levels as they get old ¹. How large the decline is in muscle, liver and blood in people, and whether it causes anything or merely accompanies ageing, is still argued.

Giving NAD+ itself

The surprising thing is how little has been published on NAD+ given directly. The one controlled study is a 2019 pilot in which eight volunteers received 750 mg of NAD+ by intravenous infusion over six hours and three received saline, with blood and urine sampled throughout ⁴. Plasma NAD+ did not rise at all for the first two hours despite the infusion, which the authors read as the molecule being taken up or broken down as fast as it went in; levels rose after that, and products of its breakdown appeared in urine ⁴. Eleven people, one day, and no outcome measured beyond blood chemistry: that is the published trial record for NAD+ infusions, which are nonetheless offered in clinics. NAD+ is not an approved drug anywhere.

What the precursor trials found

Nearly every trial that gets quoted for NAD+ gave a precursor by mouth. In a 2018 crossover study, 24 healthy adults aged 55 to 79 took 1,000 mg a day of nicotinamide riboside for six weeks; blood NAD+ rose by about 60%, the supplement was well tolerated, and there were hints of lower blood pressure and arterial stiffness that the study was too small to confirm ⁵. In a 2018 trial in 40 obese, insulin-resistant men, 2,000 mg a day of nicotinamide riboside for 12 weeks raised NAD+ metabolites but did not change insulin sensitivity, body composition or energy expenditure ⁶. NMN, the other precursor, has its own guide; its human trials are of the same shape — blood NAD+ goes up, and the clinical measures mostly stay where they were, or move a little.

What is not known

No trial has shown that raising NAD+ changes how long people live, how fast they age, or any hard clinical outcome. The mouse studies that motivated the human trials reported better muscle, blood-vessel and metabolic measures when NAD+ was raised in old animals, and that is the hopeful part. But "NAD+ falls with age" and "raising it slows ageing" are two different claims, and only the first has human evidence behind it. What years of raised NAD+ do to the enzymes that consume it, including the DNA-repair and immune enzymes, has not been studied in people.

What these studies are, and aren't

Small human studies. Direct human measurements that NAD+ falls with age, a single 11-person infusion pilot of NAD+ itself, and small trials of oral precursors that raise blood NAD+ without clear clinical change; no outcomes trial of any of it.