NMN (nicotinamide mononucleotide): what the trials show, and what an injectable vial does not

Nicotinamide mononucleotide is a naturally occurring molecule made from vitamin B3 (nicotinamide) and a phosphorylated ribose sugar. It is the last step before NAD+ in the salvage pathway, the route by which most cells recycle nicotinamide back into NAD+, and the enzyme that makes NMN, NAMPT, is the rate-limiting step of that pathway ^[1]. NMN is present in small amounts in foods such as broccoli, avocado and edamame, and in human blood and tissues.

NMN is not a peptide. A peptide is a chain of amino acids; NMN is a single nucleotide with a molecular weight of 334 and contains no amino acids ^[14]. It appears on PepFinder because the stores that sell research peptides also sell it, as capsules, sublingual powder and, increasingly, as a lyophilised powder in injectable vials, and because shoppers search for the NMN peptide alongside NAD+, which the same stores sell for injection.

Interest in NMN grew out of work on NAD+ and ageing, led by Shin-ichiro Imai at Washington University in St Louis and others, showing that NAD+ levels fall with age in mice and that restoring them with NMN reverses some age-related changes ^[1][2]. The human trials that followed are the subject of this guide.

NAD+ is the coenzyme that carries electrons in the reactions that turn food into ATP, and it is also consumed by three families of enzymes: sirtuins, which regulate gene expression and metabolism; PARPs, which repair DNA; and CD38, an enzyme on immune cells that breaks NAD+ down. Because these consumers compete for a limited pool, and because the pool declines with age in mice and in some human tissues, raising the supply of precursors is the logic behind NMN, nicotinamide riboside (NR) and NAD+ itself ^[1].

Taken by mouth, NMN reaches the blood quickly. A 2020 Japanese study gave single doses of 100, 250 and 500 mg to ten healthy men and found that its breakdown products in blood rose over the following hours without any change in heart rate, blood pressure, temperature or oxygen saturation ^[3]. Several longer trials have since shown that blood NAD+ rises within two to four weeks of daily dosing and stays raised for as long as dosing continues ^[5][6][9]. What is still debated is how much NMN enters cells intact and how much is first broken down to nicotinamide and rebuilt.

The NMN vs NAD question that shoppers ask is one of route and evidence. NAD+ is a larger molecule that cannot be absorbed intact and is given by injection or drip; NMN is absorbed after oral dosing and has the larger trial record. Our NAD+ guide compares the two, and 5-amino-1MQ, another product in the same category, is claimed to raise NAD+ by blocking an enzyme that consumes nicotinamide.

In mice, the case for NMN is strong. A 12-month study of oral NMN in ageing mice found that it suppressed age-related weight gain, increased energy expenditure and physical activity, improved insulin sensitivity and lipid profiles, and improved eye function, without obvious toxicity ^[2]. Mouse results, however, come from doses of 100 to 300 mg per kilogram, far above any human dose, and the human trials have been smaller in effect.

Insulin sensitivity: in 2021, researchers at Washington University published the first placebo-controlled NMN trial with a hard physiological outcome. Postmenopausal women with prediabetes who were overweight or obese took 250 mg a day for ten weeks. Insulin-stimulated glucose disposal in muscle, measured by the clamp technique, and insulin signalling in muscle biopsies increased with NMN but not placebo; body composition, blood pressure and other metabolic measures did not change ^[4].

Physical performance: a 60-day trial of 80 healthy middle-aged adults randomised to placebo, 300, 600 or 900 mg a day found that blood NAD+ rose in a dose-dependent way, six-minute walking distance improved in all NMN groups compared with placebo, and a blood-based biological age score rose in the placebo group but not in the NMN groups. The 600 mg dose gave the best results and 900 mg added nothing ^[5]. A six-week trial in 48 amateur runners taking 300 to 1,200 mg a day alongside training found dose-dependent improvements in aerobic capacity at the ventilatory threshold ^[7].

Older adults: a 12-week trial of 250 mg in 108 older Japanese adults found that afternoon dosing improved a sit-to-stand test and reduced drowsiness more than morning dosing or placebo ^[8]. A 12-week trial in older men found raised blood NAD+ and nominal improvements in gait speed and one grip-strength test, but no change in body composition, and the authors called for larger studies ^[9].

Weight and lipids: a 28-day study of a pharmaceutical NMN formulation, MIB-626, at 1,000 mg twice daily in 30 overweight or obese adults over 45 reported a 1.9 kg greater fall in body weight than placebo, together with lower diastolic blood pressure, total cholesterol and LDL cholesterol ^[10]. A 60-day trial of 300 mg in 66 adults reported a 38% rise in serum NAD+/NADH against 14% with placebo and a small improvement in a quality-of-life questionnaire, but no change in insulin resistance ^[11].

The pattern across trials is consistent on one point and mixed on the rest. Every placebo-controlled oral trial that measured blood NAD+ found it rose ^{[5][6][9][10][11]}. The clinical outcomes are less uniform: the prediabetes trial found a change in muscle insulin sensitivity but not in whole-body measures ^[4]; the 80-person dose-ranging trial found better walking distance but no change in insulin resistance ^[5]; the older-men trial found only nominal changes in physical tests ^[9]; and a 12-week trial of 250 mg in 30 healthy adults found raised NAD+ and no abnormalities in laboratory tests but was not designed to measure clinical benefit ^[6].

All of these trials are short, most have fewer than 100 participants, and several were funded or supplied by NMN manufacturers. None has measured whether NMN affects ageing, lifespan or disease in people, and the largest human outcome, walking distance in healthy adults, is a modest one. What the trials do establish is that oral NMN at 250 to 1,000 mg a day raises blood NAD+ and was tolerated over 4 to 12 weeks.

Blood NAD+ rises within the first month: the 80-person trial saw significant increases at day 30 that were maintained at day 60 ^[5], the Uthever trial saw an 11% rise at day 30 and 38% at day 60 ^[11], and the pharmaceutical MIB-626 raised NAD+ substantially within 28 days ^[10]. Physical measures, where they changed, did so over the 6 to 12 weeks of the trials ^[5][7][8]. Nothing is known about effects beyond 12 weeks, because no controlled trial has lasted longer.

Published trials used oral doses of 250 mg a day ^[4][6][8][9], 300 mg a day ^[11], 300 to 900 mg a day ^[5], 300 to 1,200 mg a day ^[7], and 1,000 mg twice a day ^[10]. Single doses up to 500 mg were tested for safety in the first human study ^[3]. In the dose-ranging trial, 600 mg gave the largest rise in NAD+ and the longest walking distances, and 900 mg added no further benefit ^[5].

These are the doses studies used, not recommendations. The right dose for any individual purpose has not been established, and the trials measured surrogate markers rather than long-term outcomes. For anyone reconstituting an injectable vial, our peptide calculator does the arithmetic, but no human trial supports that route.

Every randomised trial of NMN used oral capsules or tablets ^{[4][5][6][7][8][9][10][11]}. Sublingual powders are marketed on the theory that they bypass the gut, but we found no controlled trial comparing them with swallowed NMN. Peptide stores sell NMN as a lyophilised powder for subcutaneous injection; the only published human data on any injected route is a 2022 report of a single intravenous infusion in ten healthy volunteers, which found no changes in ECG, pulse, blood pressure or organ markers and a rise in blood NAD+ ^[12]. That is a safety observation in ten people, not evidence that injecting NMN does anything an oral dose does not.

In the trials, NMN was well tolerated: adverse events were similar to placebo, and routine blood tests, liver and kidney markers and physical examinations showed no adverse changes over 4 to 12 weeks at up to 900 mg a day ^[5][6][9] and at 2,000 mg a day for 28 days in the MIB-626 study ^[10]. The first human study noted small changes in bilirubin, creatinine and glucose that stayed within normal ranges ^[3].

What the trials cannot tell you is what happens over years. Concerns raised in the scientific literature, rather than observed in trials, include the theoretical possibility that raising NAD+ could support the growth of existing cancers, and the effects of long-term high doses on the liver, where nicotinamide is metabolised ^[1]. No trial has run long enough to test either. Injected NMN from a research supplier adds the usual risks of unlicensed injectables: unknown purity, endotoxin and non-sterile preparation.

NMN and NR are both NAD+ precursors with randomised human trials; NAD+ itself, given by injection or drip, has a small pharmacokinetic study and clinic reports, as set out in our NAD+ guide. NR has its own trial record and is sold as a supplement under the name Niagen. Head-to-head comparisons are few, and both precursors raise blood NAD+. The practical differences are regulatory status, cost and form: NMN is now sold as a supplement in the US after a period of uncertainty, and neither precursor has been shown to be better than the other for any clinical outcome.

Stores also market NMN alongside MOTS-c and 5-amino-1MQ as an anti-ageing stack. No study has tested those combinations in people.

NMN is not an approved medicine anywhere. In the US its status as a dietary supplement has changed twice. In November 2022 the FDA said NMN was excluded from the definition of a dietary supplement because it had been authorised for investigation as a new drug (the MIB-626 programme) before being marketed as a supplement. After a citizen petition and a lawsuit by the Natural Products Association, the FDA reversed that position in letters dated 29 September and 2 December 2025, concluding that NMN is not excluded from the supplement definition and can be marketed as a dietary ingredient ^[13]. See our US legal status page.

In the UK and EU, NMN is treated as a novel food, which means it needs authorisation before it can be sold as a food supplement; products are nonetheless widely available online. Australia’s TGA does not list NMN as an approved ingredient in listed medicines. Injectable NMN from a peptide store is an unlicensed product in every market. See our legal status overview and the UK page.

NMN degrades with heat and moisture, and its stability is one reason manufacturers argue about crystalline forms. Sealed capsules and powders are usually stored cool and dry, and some brands recommend refrigeration after opening. Reconstituted injectable powder is far less stable and should be treated like any peptide solution: refrigerated and used within days. See our guides to how to store peptides and bacteriostatic water.

Purity matters more for NMN than for most supplements, because low-grade material can contain nicotinamide and other breakdown products rather than NMN itself. A certificate of analysis should show identity at 334 g/mol ^[14] and a purity by HPLC, and the better manufacturers publish stability data. Compare NMN prices, read how to read a COA, and see our list of third-party tested suppliers.

We track NMN listings in the UK and the US. Because NMN is cheap to make in bulk, very low prices are less suspicious than they would be for a peptide, but our guides to third-party peptide testing and spotting a fake supplier still apply to injectable products.