NAD+ is a coenzyme every cell uses to move electrons through energy metabolism and to fuel the enzymes that repair DNA. Levels fall with age. Supplements do not contain NAD+ itself but a precursor, usually nicotinamide riboside, which Great Britain authorises at a maximum of 300 mg a day. The trials people quote used 1 000 to 2 000 mg.
That last sentence is the whole story, and no British page about NAD+ prints it. The research is real, the decline with age is real, and the doses that produced the results are three to six times what a legally sold supplement here may deliver.
What follows is the biology, the human trials with their negative results left in, the exact legal position of each form sold in the UK, and where injections and drips sit.
What does NAD+ do in your body?
Nicotinamide adenine dinucleotide, NAD+ for short, is a coenzyme present in every cell you have. It does two jobs that have nothing much to do with each other, which is why it gets described in two completely different ways.
The first is metabolic. NAD+ carries electrons. It accepts them from the breakdown of food, becoming NADH, and delivers them to the mitochondrial machinery that makes ATP. Without NAD+ cycling between its two states, energy metabolism stops. That is textbook biochemistry and it is not controversial.
The second is regulatory, and it is why NAD+ ended up in ageing research at all. A group of enzymes consume NAD+ as a substrate rather than recycling it: the sirtuins, which influence how genes are switched on and off, and PARPs, which repair damaged DNA. Every time those enzymes work, a molecule of NAD+ is used up. Covarrubias and colleagues set out this dual role in Nature Reviews Molecular Cell Biology in 2021.
Where NAD+ comes from and where it goes
The decline with age is the premise everything else rests on, and it is better established in animals than in people. Covarrubias and colleagues note that chronic inflammation and rising activity of NAD-consuming enzymes both contribute, meaning the pool shrinks from two directions at once. That decline is one entry on the research map of ageing rather than a diagnosis, and it is a map with very few randomised human outcomes on it.
Is NAD+ just vitamin B3?
Chemically the precursors are all forms of vitamin B3. Legally, in Great Britain, the answer is sharper than that, and it is worth knowing before you read a label.
The Great Britain Nutrition and Health Claims Register lists six authorised claims for niacin: that it contributes to normal energy-yielding metabolism, to normal functioning of the nervous system, to normal psychological function, to the reduction of tiredness and fatigue, to the maintenance of normal skin, and to normal mucous membranes.
There is not a single authorised claim for nicotinamide riboside, for nicotinamide mononucleotide, or for NAD+ itself. Search the register for riboside or mononucleotide and nothing comes back.
The practical consequence is odd and worth sitting with. A plain niacin tablet costing a few pounds may lawfully say it reduces tiredness and fatigue. A premium nicotinamide riboside product may not say that, or anything else about what it does. Since 1 January 2021 that register has been the only list a supplement sold in England, Scotland or Wales may draw health claims from, Northern Ireland having stayed with the EU list.
That does not make the precursors interchangeable. Trammell and colleagues, in Nature Communications in 2016, ran the first clinical pharmacokinetic study of nicotinamide riboside and showed it raises the blood NAD+ metabolome with distinct and, in mice, superior kinetics to nicotinic acid and nicotinamide. They also identified nicotinic acid adenine dinucleotide as a highly sensitive biomarker that NAD+ has genuinely been replenished. The headline figure, a 2.7-fold rise in blood NAD+ after a single oral dose, came from a pilot in one individual, which is worth remembering whenever you see it quoted.
Is NAD+ legal in the UK?
Partly, and the detail matters more than the headline. Each form sits in a different regulatory box.
| Form | Status in Great Britain | What that means for you |
|---|---|---|
| Nicotinamide riboside chloride | Authorised novel food since 20 February 2020, applicant ChromaDex | Legal to sell, capped at 300 mg a day in food supplements, and 230 mg a day for pregnant and breastfeeding women. |
| Nicotinamide mononucleotide (NMN) | Not authorised. Application RP-2116 by Effepharm is at the risk assessment stage, the first of three | It has not completed the process. Products containing it are on sale ahead of authorisation. |
| Niacin, nicotinamide, nicotinic acid | Permitted vitamin forms with six authorised health claims | The only part of this shelf that may lawfully tell you what it does. |
| NAD+ by intravenous drip or injection | Not an NHS treatment and not a licensed medicine | Delivered privately. In England, administering intravenous products to enhance wellbeing is a regulated activity requiring CQC registration. |
The novel food rule exists because nicotinamide riboside was not eaten to a significant degree in Britain or the EU before May 1997, so it had to be assessed for safety before it could be sold. That assessment set the 300 mg ceiling. NMN has not finished the same process.
The dose gap: what the trials used against what you can buy
This is the section that changes how you read every other page on the subject. Line up the doses.
DAILY DOSE OF NICOTINAMIDE RIBOSIDE, TRIALS AGAINST THE BRITISH LEGAL CEILING
Trammell 2016 tested single doses of 100, 300 and 1 000 mg and found dose-dependent rises in the blood NAD+ metabolome. Martens and colleagues, in Nature Communications in 2018, gave 1 000 mg a day for six weeks to healthy middle-aged and older adults in a crossover trial: well tolerated, and it effectively stimulated NAD+ metabolism. Their blood pressure and arterial stiffness findings were preliminary, and the paper itself says future trials should assess them.
Elhassan and colleagues, at the University of Birmingham, gave 1 g a day for 21 days to twelve aged men in a placebo-controlled, randomised, double-blind crossover trial, published in Cell Reports in 2019. Oral nicotinamide riboside did reach aged human muscle: the muscle NAD+ metabolome rose. It also lowered circulating inflammatory cytokines. And it did not alter mitochondrial bioenergetics, which was the thing everyone hoped it would.
Then the trial nobody links to. Dollerup and colleagues published a randomised, placebo-controlled, double-blind, parallel-group trial in the American Journal of Clinical Nutrition in 2018: forty sedentary obese men, aged 40 to 70, on 1 000 mg of nicotinamide riboside twice a day, so 2 000 mg, for twelve weeks. Insulin sensitivity was measured properly with a hyperinsulinaemic euglycaemic clamp.
Nothing improved. Not insulin sensitivity, not glucose production or disposal, not resting energy expenditure, not lipolysis, not fat oxidation, not body composition. Twelve weeks at nearly seven times the British legal ceiling produced no metabolic benefit. It was safe, which is a genuine finding, but it was not effective for what it tested.
WHAT IS ESTABLISHED
Oral precursors raise the NAD+ metabolome in human blood and muscle, dose-dependently, and at 1 to 2 g a day they are well tolerated.
WHAT IS SUGGESTIVE
Lower inflammatory cytokines in aged muscle, improved muscle insulin sensitivity in prediabetic postmenopausal women on NMN, preliminary vascular signals.
WHAT HAS FAILED SO FAR
No change in mitochondrial bioenergetics. No improvement in insulin sensitivity or body composition in obese men at 2 g a day for twelve weeks.
Do NAD+ supplements really work?
It depends entirely on what you mean by work, and the honest answer splits in two. The benefits people expect from this shelf are subjective ones, more energy and sharper thinking, and those are not what the trials measured.
Do they raise NAD+? Yes. That is measured, repeated and dose-dependent. Trammell 2016 and Martens 2018 both show it clearly, and Elhassan 2019 shows an oral precursor reaching muscle in older people. If the premise is that a shrinking pool is the problem, a precursor does help refill it.
Do they change something you would notice? That has not been shown. The clearest positive human result is Yoshino and colleagues in Science in 2021, a ten-week randomised placebo-controlled trial of nicotinamide mononucleotide in postmenopausal women with prediabetes who were overweight or obese. Insulin-stimulated glucose disposal rose, muscle insulin signalling improved, and genes related to muscle remodelling were upregulated.
Read the population again. Postmenopausal, prediabetic, overweight or obese women, and the outcome was measured with a clamp in a laboratory. Nothing in it says a healthy 45-year-old will feel different, and NMN is the form Britain has not authorised.
There is also a regulator’s view on this now. On 4 February 2026 the Advertising Standards Authority upheld a complaint against Kind Patches Ltd over adverts for a NAD+ patch. The wording promised to “reverse the signs of aging naturally”, along with better focus and memory and support for DNA repair, in ruling A25-1310978. The ASA found the claims unsubstantiated and the ads misleading under CAP Code rules 3.1, 3.7 and 12.1. It has taken the same line against collagen brands, for the same reason: a specific health claim in an advert has to exist on the register first. Part of its reasoning is the theme of this whole article: the clinical trials submitted as evidence had used oral administration, in quantities greater than the product contained.
Is NAD+ like Ozempic?
No, and the question is worth answering plainly because the two have started appearing in the same conversations.
Semaglutide, sold as Ozempic and Wegovy, is a GLP-1 receptor agonist. It is a licensed prescription medicine with an authorised indication, a marketing authorisation, phase 3 trials behind it and a known safety profile. It works by mimicking a gut hormone that slows gastric emptying and reduces appetite.
NAD+ precursors are food supplements or, as a drip, unlicensed. They do not act on appetite. No trial has shown weight loss. The point is worth making with the strongest evidence available in the opposite direction: in Dollerup 2018, twelve weeks at 2 000 mg a day changed nothing about body composition or energy expenditure in obese men, and in Yoshino 2021 body composition did not change either.
The two are being sold in the same private clinics, sometimes on the same page. That is a commercial fact, not a pharmacological one.
Drips, injections and what the downside is
NAD+ infusions are sold privately in Britain, typically in courses, at a price that makes a bottle of capsules look trivial. Three things are true about them.
They are not an NHS treatment. They are not a licensed medicine, so no regulator has assessed a specific NAD+ infusion product for efficacy in the way it would assess a drug. And in England, giving intravenous vitamins or prescription-only products to enhance wellbeing counts as treatment of disease, disorder or injury under the Health and Social Care Act 2008, which means the clinic must be registered with the Care Quality Commission. Carrying on that regulated activity without registration is an offence. If you are considering a drip, checking the provider on the CQC register is the single most useful thing you can do.
As for downsides of the oral form, the trials are reassuring on safety and thin on everything else. Dollerup 2018 recorded no serious adverse events at 2 000 mg a day for twelve weeks and normal safety bloods. Martens 2018 found 1 000 mg a day well tolerated over six weeks. Reported effects are mild and gastrointestinal: nausea, bloating, indigestion. High-dose nicotinic acid, a different B3 form, causes the well known flush; nicotinamide riboside does not.
The real downside is not physiological. It is that long-term safety beyond twelve weeks has not been studied, that the doses studied are not the doses you can buy here, and that the money is substantial. The trials also recruited narrow groups, so people with liver or kidney conditions, on medication, or pregnant or breastfeeding are outside the evidence entirely and should ask a pharmacist or GP rather than a retailer.
If what sent you looking at NAD+ was stiff, aching joints rather than an interest in cellular metabolism, the honest answer is that this is not the shelf for it. The evidence for NAD+ is about metabolism and inflammatory markers, not about pain. Support formulated for ageing joints and a properly absorbed bioavailable anti-inflammatory answer that question directly. Neither treats a diagnosed condition, and persistent pain is a reason to see your GP.
Frequently asked questions
What does NAD+ do in your body?
Two jobs. It carries electrons from the breakdown of food to the mitochondria, cycling between NAD+ and NADH, which is how cells make energy. And it is consumed as a substrate by sirtuins, which regulate gene activity, and PARPs, which repair damaged DNA. That second role is why it appears in ageing research.
Is NAD+ legal in the UK?
Nicotinamide riboside chloride is an authorised novel food in Great Britain, legal since 20 February 2020, capped at 300 mg a day in food supplements. Nicotinamide mononucleotide is not authorised: its application is still at the risk assessment stage. Intravenous NAD+ is not a licensed medicine and is given privately, not on the NHS.
Is NAD+ just vitamin B3?
The precursors are B3 forms, but the legal position separates them sharply. Niacin carries six authorised health claims on the Great Britain register, including reduction of tiredness and fatigue. Nicotinamide riboside, nicotinamide mononucleotide and NAD+ itself carry none, so a premium product may not tell you what it does.
Do NAD+ supplements really work?
They reliably raise NAD+ levels in blood and muscle, dose-dependently, which is measured and repeated. Whether that produces an effect you would notice is unproven. The clearest positive trial, on NMN in prediabetic postmenopausal women, improved muscle insulin sensitivity measured with a clamp, not anything the participants could feel.
What is the downside of taking NAD?
Reported side effects are mild and gastrointestinal: nausea, bloating, indigestion. The bigger problems are that no trial has run beyond about twelve weeks, that the doses studied were 1 000 to 2 000 mg a day while Britain caps supplements at 300 mg, and that the cost is high for an unproven subjective benefit.
Is it safe to take NAD+ daily?
In trials, yes, over the periods studied. Dollerup 2018 gave 2 000 mg a day for twelve weeks with no serious adverse events and normal safety bloods, and Martens 2018 found 1 000 mg a day well tolerated over six weeks. Nothing has been studied for longer, and there is no safety data in pregnancy or breastfeeding at these doses.
Is NAD+ like Ozempic?
No. Semaglutide is a licensed prescription medicine, a GLP-1 receptor agonist that acts on appetite and gastric emptying, with phase 3 trials behind it. NAD+ precursors are food supplements that do not act on appetite, and no trial has shown weight loss. In the largest negative trial, body composition did not change at all.
Sources
- Covarrubias A.J., Perrone R., Grozio A., Verdin E. NAD+ metabolism and its roles in cellular processes during ageing. Nature Reviews Molecular Cell Biology, 2021. DOI: 10.1038/s41580-020-00313-x
- Trammell S.A.J., Schmidt M.S., Weidemann B.J., et al. Nicotinamide riboside is uniquely and orally bioavailable in mice and humans. Nature Communications, 2016. DOI: 10.1038/ncomms12948
- Elhassan Y.S., Kluckova K., Fletcher R.S., et al. Nicotinamide riboside augments the aged human skeletal muscle NAD+ metabolome and induces transcriptomic and anti-inflammatory signatures. Cell Reports, 2019. DOI: 10.1016/j.celrep.2019.07.043
- Martens C.R., Denman B.A., Mazzo M.R., et al. Chronic nicotinamide riboside supplementation is well-tolerated and elevates NAD+ in healthy middle-aged and older adults. Nature Communications, 2018. DOI: 10.1038/s41467-018-03421-7
- Dollerup O.L., Christensen B., Svart M., et al. A randomized placebo-controlled clinical trial of nicotinamide riboside in obese men: safety, insulin-sensitivity, and lipid-mobilizing effects. The American Journal of Clinical Nutrition, 2018. DOI: 10.1093/ajcn/nqy132
- Yoshino M., Yoshino J., Kayser B.D., et al. Nicotinamide mononucleotide increases muscle insulin sensitivity in prediabetic women. Science, 2021. DOI: 10.1126/science.abe9985
Regulatory positions in this article were checked on 30 August 2026 against the Food Standards Agency register of authorised novel foods (NOVEL-96) and its register of regulated product applications (RP-2116), the Great Britain Nutrition and Health Claims Register, and Advertising Standards Authority ruling A25-1310978 of 4 February 2026.
This article is general information, not medical advice. Food supplements do not replace a varied diet. No health claim for NAD+, nicotinamide riboside or nicotinamide mononucleotide is authorised in Great Britain. If you are pregnant or breastfeeding, take prescribed medicines, or have liver or kidney disease, speak to your GP or pharmacist before taking any NAD+ precursor.
