Skip to content
What Is NMN and Is It Safe in the UK? What the Human Trials Found
NMN, nicotinamide mononucleotide, is the molecule your cells convert in one step into NAD+, a coenzyme every cell uses to turn food into energy and to run its repair enzymes. Your body already makes NMN from nicotinamide, a form of vitamin B3. As a capsule it raises blood NAD within weeks. In the largest trial, 80 healthy middle-aged adults took 300, 600 or 900 mg a day for 60 days and walked further in a six-minute test than the placebo group, most at 600 mg; insulin resistance did not change.1 Across 15 pooled trials at 250 to 2,000 mg a day for up to 24 weeks, NMN did not raise liver enzymes or adverse events, or change body weight, fasting glucose, HbA1c or cholesterol.2, 3 NMN is sold as a food supplement in the UK; it is not a medicine and is not banned. Nothing is known about years of use; the longest trial is 24 weeks.
- What trials measured: higher blood NAD; a longer six-minute walk; no change in glucose, lipids or weight
- Who should not take it: pregnant and breastfeeding women, under-18s; anyone with a cancer diagnosis or on medicines asks first
What is NMN, and how is it different from NAD?
NAD+ is the working molecule: cells use it to shuttle electrons while burning glucose and fat, and the enzymes that repair DNA consume it as fuel. NMN is the raw material one step upstream; an enzyme adds a second nucleotide and the result is NAD+. Your cells make NMN constantly from nicotinamide, the form of vitamin B3 in meat, fish, eggs and fortified cereals.4 So "should I take NMN or NAD?" is a question about a pathway, not a choice between products: oral NAD+ has far fewer trials than its precursors, and NMN has the most. Nicotinamide riboside is a different molecule one step further back. Whether raising blood NAD changes anything about ageing in a human body has not been established.8
Is NMN just vitamin B3?
Close to it. The European Food Safety Authority's 2026 assessment treated NMN as a bioavailable source of nicotinamide with a conversion factor of 1, so a 300 mg capsule supplies about 110 mg of nicotinamide, roughly five times the daily reference intake of niacin (16 mg) and well under the 900 mg upper level for nicotinamide.4 That settles what NMN becomes in the body. Whether NMN does anything plain nicotinamide would not is unsettled, because no human trial has compared the two on an outcome you would notice. The NHS has no page on NMN; its vitamin B page covers niacin.10
What did the human trials of NMN find?
Fifteen placebo-controlled trials, 250 to 2,000 mg a day, two to 24 weeks, mostly in adults over 40. Every one that measured blood NAD saw it rise; the functional findings come from single trials.
| Trial | People and dose | What it found |
|---|---|---|
| Yi 20231 | 80 healthy adults, 40 to 65; 300, 600 or 900 mg; 60 days | Six-minute walk longer than placebo, most at 600 mg; insulin resistance unchanged |
| Igarashi 20225 | 42 healthy older men; 250 mg; 6 or 12 weeks | Blood NAD rose; gait and grip changes the authors said need confirming |
| Yoshino 20216 | 25 postmenopausal women with prediabetes; 250 mg; 10 weeks | Muscle insulin sensitivity rose on NMN, not on placebo |
| Kim 20227 | 108 older Japanese adults; 250 mg, morning or afternoon; 12 weeks | Afternoon NMN reduced daytime drowsiness; sleep quality unchanged |
| Pooled, Yang 20262 | 15 trials; 250 to 2,000 mg; up to 24 weeks | No rise in adverse events or liver enzymes; no change in weight, glucose, HbA1c or lipids |
A 2025 review of 12 trials put it more sharply: blood NAD rises, most clinically relevant outcomes do not differ from placebo, and the authors warned against exaggerating the benefits.8 A longer walk in one good trial is a real finding; "reverses ageing" is not something any trial has measured.
Does NMN give you more energy?
The nearest evidence is the walking test and the afternoon-drowsiness finding.1, 7 Neither measures how you feel at four o'clock, which is what the forum reports describe: roughly two "fewer naps" to every "nothing". The biology behind the advert: NAD sits in the middle of energy metabolism, and niacin, which NMN becomes, contributes to normal energy-yielding metabolism and to the reduction of tiredness and fatigue. To find out whether NMN does anything for you, run the trials' test: 60 days, one change, something you can score before and after.
Can NMN change grey hair or make you look younger?
No human trial has measured hair colour, skin or appearance on NMN. A hair that has already grown grey has no pigment in its shaft and cannot re-colour; only new growth could differ, and no human study looked at the follicle. The idea comes from mouse work on NAD and pigment cells.9 The long forum threads on NMN and grey hair tend to carry affiliate codes. The "biological age" result in the 60-day trial was a calculation from blood markers, not a mirror.1
Is NMN linked to cancer?
The fear comes from a 2025 conference abstract in which mice bred to develop cancer grew tumours faster when given NMN. It is an abstract, not a full paper, in animals engineered to get the disease. In the 15 human trials, adverse events were no higher on NMN than on placebo, and the European assessment found no genotoxicity concern.2, 4 The worry has a basis in principle, because cancer cells use NAD too; what it means after years of 300 mg is unknown, because nobody has been followed that long. Anyone with a current or past cancer diagnosis should ask their oncology team before taking NMN or any NAD precursor.
Is NMN hard on the liver?
Not in the trials. Across 15 studies at up to 2,000 mg a day for up to 24 weeks, the liver enzymes ALT and AST did not rise.2 No headache signal appears in the pooled adverse events, and weight moved in neither direction, so "can NAD cause weight gain?" is also answered: no.
Can you take NMN when pregnant, breastfeeding or trying to conceive?
No. The European assessment judged 300 mg a day safe for adults but excluded pregnant and breastfeeding women, partly because a 90-day rat study at high doses showed effects on reproductive organs, with a margin judged sufficient for other adults.4 There is no human trial of NMN for egg quality, IVF or fertility in either sex; the data quoted are from animals. Anyone in fertility treatment should ask their clinic first.
Does NMN raise oestrogen or testosterone?
No human trial has measured either. The trials in men looked at NAD, walking and grip; the trial in women at muscle insulin sensitivity.5, 6 Hot flushes, hangovers and brain fog on HRT have not been studied; taking NMN alongside HRT is a question for the prescriber.
Who should not take NMN?
Pregnant and breastfeeding women; under-18s, since the safety assessment covers adults only; anyone with a cancer diagnosis without their team's agreement; and anyone on prescribed medicines until they have told their pharmacist, since no interaction has been looked for. Take it with food and don't exceed the stated dose.
How to read an NMN label
Look for the milligrams of NMN itself, written as beta-nicotinamide mononucleotide or beta-NMN, per capsule; a front-of-pack "NAD+ complex 500 mg" is the weight of a blend. The trials used 250 to 900 mg a day, and 600 mg is where the 60-day trial saw its largest walking effect.1 Check the niacin line, where the authorised wording lives, and the resveratrol line if there is one (our resveratrol guide covers it). Wellgard's Beta NMN capsules supply 300 mg of NMN a day with 37.5 mg of trans-resveratrol, niacin at 20% of the reference intake and vitamin E at 20%; 300 mg equals the lowest arm of the 2023 trial and the level the European safety opinion assessed, and niacin contributes to normal energy-yielding metabolism and to the reduction of tiredness and fatigue, while vitamin E contributes to the protection of cells from oxidative stress.1, 4 How long to give it is in what happens when you stop taking NMN; for the molecule with far more human trials, see the Wellgard berberine guide.
Frequently asked questions
Is NMN banned in the UK or the US?
NMN is sold as a food supplement in the UK; it is not a medicine and is not banned. In the United States the regulator queried its supplement status in late 2022 and reversed that position in September 2025; the marketplace delistings date from the first of those.
Which foods are high in NMN?
None usefully. Edamame, broccoli, cucumber, cabbage, avocado and tomato hold roughly 0.25 to 1.9 mg per 100 g; a 300 mg capsule equals tens of kilograms of vegetables.9
Does NMN do what the weight-loss injections do?
No. Pooled trials show no change in body weight,2 and the injectable medicines act on a gut-hormone receptor unrelated to NMN.
Is NMN actually worth it, and why is it so expensive?
Synthesising a stable nucleotide is costly; that is the price story. Worth is a 60-day test with something measurable, since the trials found a longer walk and higher blood NAD, not anything guaranteed to be felt.1
What is the difference between NAD and astaxanthin?
Unrelated molecules: NAD is a coenzyme made from vitamin B3, astaxanthin a red pigment from algae.
Sources
- Yi L, et al. The efficacy and safety of β-nicotinamide mononucleotide (NMN) supplementation in healthy middle-aged adults: a randomised placebo-controlled trial. GeroScience, 2023. PubMed 36482258.
- Yang W, et al. Safety and metabolism-related outcomes of oral nicotinamide mononucleotide supplementation in adults: meta-analysis. Nutrients, 2026. PubMed 42514320.
- Chen F, et al. Effects of nicotinamide mononucleotide on glucose and lipid metabolism in adults: meta-analysis. Current Diabetes Reports, 2024. PubMed 39531138.
- EFSA NDA Panel. Safety of beta-nicotinamide mononucleotide (β-NMN) as a novel food and source of nicotinamide. EFSA Journal, 2026. PubMed 42125559.
- Igarashi M, et al. Chronic nicotinamide mononucleotide supplementation in healthy older men. npj Aging, 2022. PubMed 35927255.
- Yoshino M, et al. Nicotinamide mononucleotide increases muscle insulin sensitivity in prediabetic women. Science, 2021. PubMed 33888596.
- Kim M, et al. Nicotinamide mononucleotide for 12 weeks: sleep, fatigue and physical performance in older Japanese adults. Nutrients, 2022. PubMed 35215405.
- Zhang J, et al. Efficacy of oral nicotinamide mononucleotide supplementation on glucose and lipid metabolism for adults: meta-analysis. Critical Reviews in Food Science and Nutrition, 2025. PubMed 39116016.
- Mills KF, et al. Long-term nicotinamide mononucleotide administration in mice (includes food NMN contents). Cell Metabolism, 2016. PubMed 28068222.
- NHS. B vitamins and folic acid. nhs.uk/conditions/vitamins-and-minerals/vitamin-b.
This article is general information, not medical advice; if you are pregnant, breastfeeding, under 18, have had cancer or take prescribed medicines, ask your GP or pharmacist before taking NMN.
