What the evidence shows: NAD+ goes up, health measures mostly don’t move
This review draws on two meta-analyses that pool the human trials, two of the trials themselves and mouse lifespan studies1510. It also covers the regulatory history and an independent test of what NMN products actually contain69.
In the US, NMN has been through an on-again, off-again fight over whether it can be sold as a supplement at all67. FDA’s 2025 reversal turned on drug-versus-supplement rules78. In mice, the lifespan results are mixed45. A closely related NAD+ booster didn’t extend lifespan in a multi-drug study in genetically diverse mice4.
The one consistent result is biochemical. A 12-week randomized, double-blind trial enrolled healthy Japanese men aged 65 and over2. Taking 250 mg of NMN a day raised NAD+ and related compounds in their blood compared with placebo2.
A 60-day randomized, double-blind trial in India enrolled 80 healthy adults aged 40 to 653. Doses of 300, 600 and 900 mg a day all raised blood NAD+ compared with placebo3. The 600 mg dose raised it more than 300 mg, but 900 mg did no better than 600 mg3.
Metabolic health hasn’t followed. A 2025 meta-analysis of metabolic effects pooled eight double-blind randomized trials with 342 adults1. They were mostly middle-aged and mostly in Asia, and most had normal blood sugar and cholesterol1. They took 250 to 2,000 mg a day for 14 days to 12 weeks1. NMN didn’t significantly change fasting glucose, fasting insulin, HbA1c, cholesterol, triglycerides, body mass index, blood pressure or liver enzymes1.
The closest result was for HOMA-IR, a score of insulin resistance1. Across three trials it showed a pooled reduction of 0.27 (95% CI -0.01 to 0.55; p = 0.06), which the authors called marginally significant1. That result was no longer significant once one trial was excluded1. In that trial, the difference came from HOMA-IR getting worse in the placebo group, not better with NMN1. The reviewers concluded that their findings “do not support the use of NMN supplementation among general population to improve glucose and lipid metabolism”1.
Physical function results are mixed and come from small trials. In the trial in older men, gait speed and left-hand grip strength improved more than with placebo2. The authors called these gains “nominally significant” and said they should be validated in larger studies2. Muscle mass, visceral (belly) fat, liver fat, blood sugar, blood pressure, blood vessel function and cognition didn’t change2.
That trial also had a supplier error. At the six-week visit, 11 people in each group got the other group’s supplement2. Data from 22 of the 42 participants were excluded, so only 10 people per group were analyzed at 12 weeks2. The trial’s analyses were exploratory, with no correction for multiple comparisons2.
In the 60-day trial in India, the 600 and 900 mg groups walked farther in a six-minute walk test than at the start3. The NMN groups also did better than placebo on that test and on a quality-of-life questionnaire3. Insulin resistance (HOMA-IR) didn’t differ from placebo, although it rose from baseline within the 600 and 900 mg groups3. That trial was co-sponsored by the two companies that developed the NMN product being tested3.
Pooled results on muscle show no benefit. A second 2025 meta-analysis looked at randomized trials in adults with an average age above 6010. NMN didn’t improve skeletal muscle mass (3 trials), grip strength (5 trials), gait speed (4 trials) or chair-stand time (2 trials)10. Every pooled confidence interval included no effect10. For gait speed, for example, the pooled estimate was -0.01 (95% CI -0.08 to 0.06)10.
Knee strength, a standard physical performance battery and thigh muscle mass didn’t improve either10. The authors concluded that “current evidence does not support NMN and NR supplementation for preserving muscle mass and function”10. With only two to five trials per outcome, these pooled results are imprecise10.
| Study | Who was studied | Dose and length | What it found | Main limits |
|---|---|---|---|---|
| Chen et al., 2025 meta-analysis1 | 342 adults in 8 double-blind trials, mostly middle-aged and in Asia | 250 to 2,000 mg a day for 14 days to 12 weeks | No significant change in blood sugar, insulin, HbA1c, cholesterol, triglycerides, BMI, blood pressure or liver enzymes | Small trials; mostly healthy people; too few trials to check for publication bias |
| Prokopidis et al., 2025 meta-analysis10 | Randomized trials in adults with an average age of 60.9 to 83 | Varied by trial | No significant effect of NMN on muscle mass, grip strength, gait speed or chair-stand time | Only 2 to 5 trials per outcome, so estimates are imprecise |
| Igarashi et al., 20222 | 42 healthy Japanese men aged 65 and over; 20 analyzed at 12 weeks | 250 mg a day for 12 weeks | Blood NAD+ rose; nominal gains in gait speed and left grip strength; no change in muscle mass, metabolism, blood pressure or cognition | Data from 22 of 42 participants excluded after a supplier error; exploratory; no correction for multiple comparisons |
| Yi et al., 20233 | 80 healthy adults aged 40 to 65 in India | 300, 600 or 900 mg a day for 60 days | Blood NAD+ rose at all doses; longer six-minute walk at 600 and 900 mg; no difference from placebo in insulin resistance | Short; 20 people per group; co-sponsored by the companies that developed the product tested |
What it doesn’t show: slower aging or a longer life
None of the human trials we found tested whether NMN extends life or prevents age-related disease. The randomized trials pooled in the 2025 metabolic meta-analysis lasted 14 days to 12 weeks and enrolled 14 to 108 people each1. They measured blood chemistry, walking and strength tests, and questionnaires, not illness, disability or death13.
The closest thing to an aging result is weak. In the 60-day trial, an algorithm (Aging.Ai 3.0) estimated “biological age” from 19 blood values3. That estimate stayed flat in the NMN groups and rose in the placebo group3. A 60-day shift in an algorithm’s estimate, from a small trial co-sponsored by the product’s developers, isn’t evidence that aging slowed.
The lifespan evidence comes from mice, and it’s inconsistent. A 2024 preprint gave mice NMN in their drinking water from 13 months of age5. It hadn’t been peer reviewed when it was posted5. Median lifespan rose by 8.5% in females, but males didn’t live significantly longer5.
A multi-drug lifespan study in genetically diverse mice tested nicotinamide riboside, a closely related NAD+ booster4. It didn’t significantly increase lifespan in either sex at the doses tested4. The 2025 metabolic meta-analysis also flags differences between mouse studies and human trials, including oral versus injected NMN1.
Is NMN safe? Well tolerated in short trials, unknown beyond them
In trials lasting up to 12 weeks, NMN has looked well tolerated. None of the eight trials in the 2025 metabolic meta-analysis reported safety concerns, and three reported no adverse events at all1. The 12-week trial in older men reported no serious adverse events and no lab values outside the normal range2. The 60-day trial reported no treatment-related adverse events or dropouts at doses up to 900 mg a day3.
Several caveats limit how far that goes. The reviewers noted that adverse events were reported in NMN groups taking 1,000 mg a day or more1. They called the safety of long-term use at higher doses “uncertain,” particularly in older people1. They also pointed out that oral NMN is partly converted to nicotinamide, a form of vitamin B3 with its own upper intake limit1. And they listed possible effects on tumor development as a concern1.
Most trials enrolled relatively healthy adults1. So they say little about people with medical conditions or those taking medications. Trials this small and short aren’t set up to catch rare harms or effects that take years to appear.
Can NMN be sold as a supplement? Pulled in 2022, allowed in 2025
In late 2022, FDA concluded that NMN couldn’t be sold as a dietary supplement because it had first been investigated as a drug6. The agency reached that view while reviewing a new dietary ingredient notification6. In February 2023, Amazon told sellers that NMN products “can no longer be sold or distributed as a dietary supplement” in the US6. It set a March 13, 2023, cutoff for listings6.
The Natural Products Association, a supplement trade group, pushed back with an amended citizen petition and a lawsuit in federal district court8. In two letters dated September 29, 2025, FDA reversed itself and concluded that NMN is not excluded from the definition of a dietary supplement78. The reasoning turned on timing7. FDA found enough evidence that NMN was marketed as a dietary supplement in the US before it was authorized for investigation as a drug7. The trade group then voluntarily dismissed its lawsuit without prejudice8.
In December 2025, FDA also reinstated a May 2022 letter acknowledging one manufacturer’s new dietary ingredient notification for NMN8. According to one law firm’s analysis, NMN is still treated as a new dietary ingredient7. That means each company selling it needs its own notification to FDA, unless its ingredient comes from a supplier that already filed one7. In the firm’s view, products without one remain open to enforcement7.
Being lawful to sell isn’t the same as being shown to work. Neither the 2022 decision nor its 2025 reversal was about whether NMN slows aging67. Both turned on drug-versus-supplement rules67.
- Late 2022: FDA says NMN can’t be a dietary supplement because it was first investigated as a drug6
- February 2023: Amazon tells sellers to stop listing NMN supplements by March 13, 20236
- September 29, 2025: FDA concludes NMN isn’t excluded from the dietary supplement definition78
- December 2025: FDA reinstates a 2022 acknowledgment of one company’s NMN ingredient notification8
Product quality: the label may not match the bottle
Independent testing has found wide gaps between labels and contents. A 2024 study tested 18 NMN supplements bought online, in pharmacies or directly from manufacturers9. The researchers used liquid chromatography and mass spectrometry9. Measured NMN ranged from 100% below to 11.2% above the adjusted label amount9. Three products contained no detectable NMN at all9.
The authors concluded that the label amount “poorly corresponds to the detected amount”9. They called for tighter regulation of “geroprotective” supplements9. They declared no competing financial interests9.
The study identified products by number, not brand, so it can’t tell you which products passed9. It does show that you can’t assume the dose on the label is the dose in the capsule9. That matters because the trials themselves tested specific amounts1.
Sources
- Effects of Nicotinamide Mononucleotide on Glucose and Lipid Metabolism in Adults: A Systematic Review and Meta-analysis of Randomised Controlled Trials Current Diabetes Reports, 2025 · meta-analysis
- Chronic nicotinamide mononucleotide supplementation elevates blood nicotinamide adenine dinucleotide levels and alters muscle function in healthy older men npj Aging, 2022 · randomized trial
- The efficacy and safety of β-nicotinamide mononucleotide (NMN) supplementation in healthy middle-aged adults: a randomized, multicenter, double-blind, placebo-controlled, parallel-group, dose-dependent clinical trial GeroScience, 2023 · randomized trial
- 17-a-estradiol late in life extends lifespan in aging UM-HET3 male mice; nicotinamide riboside and three other drugs do not affect lifespan in either sex Aging Cell, 2021
- Long-term NMN treatment increases lifespan and healthspan in mice in a sex dependent manner bioRxiv (preprint), 2024
- Amazon removing NMN dietary supplements, citing FDA actions NutraIngredients, 2023 · news
- FDA Declares Nicotinamide Mononucleotide Is a Dietary Supplement Venable LLP, 2025
- FDA Reinstates NMN as Dietary Supplement After NPA Lawsuit Natural Products Association, 2025
- Testing the amount of nicotinamide mononucleotide and urolithin A as compared to the label claim GeroScience, 2024
- The Effect of Nicotinamide Mononucleotide and Riboside on Skeletal Muscle Mass and Function: A Systematic Review and Meta-Analysis Journal of Cachexia, Sarcopenia and Muscle, 2025 · meta-analysis
How this was written. Written from the sources listed above, checked . It is general information, not medical advice. Talk to a clinician before acting on anything here if you have a health condition or take medication.
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