NAD+ has become one of the most talked-about molecules in the wellbeing space, often mentioned alongside energy, ageing and "cellular health". But behind the buzz sits a genuinely important piece of biology that has been studied for over a century. This article explains what NAD+ actually is, what it does inside your cells, why levels appear to change as we get older, and what the current evidence does and does not tell us.

What NAD+ actually is

NAD+ stands for nicotinamide adenine dinucleotide. It is a coenzyme, which simply means it is a small helper molecule that many of your enzymes cannot function without. And it is not a niche substance tucked away in one organ: NAD+ is present in every living cell in the body, from your muscles and brain to your skin and liver.

Your body makes NAD+ from building blocks found in the diet, including forms of vitamin B3 (niacin) and related compounds. It exists in a couple of interchangeable chemical states that let it pick up and pass along tiny electrical charges, which is the key to its role in your everyday metabolism. In other words, NAD+ is less a nutrient you store in a warehouse and more a working part that is constantly being used, recycled and remade.

What NAD+ does: energy metabolism, DNA repair and sirtuins

NAD+ has several jobs, but three stand out.

Turning food into cellular energy

The most fundamental role of NAD+ is in energy metabolism. When your body breaks down carbohydrates, fats and proteins from food, NAD+ acts as a shuttle, carrying charged particles into your mitochondria, the small structures inside cells often described as their power plants. There, this process helps produce ATP (adenosine triphosphate), the molecule your cells use as their main energy currency. Without enough NAD+, this hand-off cannot run smoothly, which is one reason the molecule is so closely linked in people's minds to the idea of energy.

Supporting DNA repair

Your DNA is under constant, everyday stress from normal cellular activity and environmental factors. Cells have repair systems that patch up this damage, and some of these systems depend on NAD+ to work. Enzymes involved in DNA repair draw on NAD+ as a resource, which is part of why researchers are interested in how NAD+ availability might relate to how cells maintain themselves over time.

Fuelling sirtuins

NAD+ is also required by a family of proteins called sirtuins. Sirtuins are involved in regulating how cells respond to stress and how certain genes are switched on or off. Because sirtuins can only act when NAD+ is present, the two are tightly connected in the laboratory research on cellular ageing and metabolism. It is worth being clear that much of this work is still at the level of cells and animal models rather than settled human outcomes.

Why NAD+ declines with age

One of the reasons NAD+ attracts so much attention is that, in laboratory and animal studies, tissue levels of NAD+ have been observed to decline with age. Researchers have proposed several explanations for this pattern. As we get older, cells may make less NAD+, use it up more quickly, or break it down faster through enzymes that consume it. The likely picture is a combination of these factors rather than a single cause.

It is important to keep this in perspective. Observing that NAD+ levels fall with age is not the same as proving that this decline causes ageing, or that topping levels back up will reverse it. These are open scientific questions, and the honest position is that the relationship between NAD+ and human ageing is still being worked out. NAD+ is not a licensed treatment for ageing in the UK, and no regulator such as the MHRA has approved it for that purpose.

How people try to raise NAD+

Because NAD+ itself is a fairly large and fragile molecule, most approaches focus on giving the body raw materials, known as precursors, that it can convert into NAD+.

  • Oral precursors: Supplements such as nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN) are among the most widely studied. The idea is that these compounds are absorbed and then used by cells to build NAD+. Standard forms of vitamin B3 also feed into NAD+ production.
  • Injections: Some clinics offer NAD+ as an injectable, which is intended to deliver the compound while bypassing digestion.
  • IV infusions: Intravenous NAD+ delivers the molecule directly into the bloodstream over a longer session, an approach that has become popular in private wellness settings.

These routes differ in how they are given, how convenient they are and how they feel, and they are not interchangeable. If you are weighing them up, our guide to NAD+ injections vs IV vs oral walks through the practical differences in more detail, and NAD+ injections: safety and side effects covers what to be aware of. Whether any form is suitable for you is a clinical decision, and a UK-registered clinician will advise based on your individual circumstances, including your health history and any medicines you take.

What the evidence currently supports, and its limits

This is where it pays to be careful and honest. The underlying biology of NAD+ is well established: its role as a coenzyme in energy metabolism, DNA repair and sirtuin activity is solid, long-standing science. What is far less certain is what happens when people take NAD+ or its precursors with the aim of improving energy, wellbeing or the ageing process.

Early human studies suggest that some oral precursors can raise measured NAD+ levels in the blood and appear to be reasonably well tolerated in the doses tested. However, evidence that this translates into clear, meaningful benefits for energy, physical performance or healthy ageing in people is still limited and early-stage. Many studies have been small, short in duration, or conducted in specific groups, which makes it difficult to draw firm conclusions for the general population. Studies suggest potential, but potential is not the same as proof.

For a fuller look at what the research does and does not show, see NAD+ for energy and ageing: the evidence. In the meantime, a sensible, plain-English summary is this: NAD+ is a genuinely important molecule, the interest in it is understandable, and the science is active but not yet settled. Bodies such as NICE do not currently recommend NAD+ supplementation as a treatment, and it should not be seen as a substitute for the fundamentals that are known to support how you feel day to day, such as sleep, physical activity, a balanced diet and managing long-term conditions.

If you are curious about NAD+, the most useful next step is an individual conversation. A GPhC-registered pharmacist or other UK-registered clinician can look at your circumstances, talk through the current evidence realistically, and help you decide whether any approach is appropriate for you rather than relying on the marketing around it.