Nicotinamide riboside and nicotinamide mononucleotide are supplement relatives of niacin that the body converts into NAD+, a molecule every cell uses for energy production and repair. Randomized trials show they reliably raise blood NAD+ and are well tolerated, while improvements in health outcomes are small, inconsistent, or absent.
NAD+ is a coenzyme that shuttles electrons during energy metabolism and acts as a co-substrate for the enzymes behind the benefits of calorie restriction. Levels fall with age and obesity in rodents, and NMN availability is a rate-limiting step in making NAD+. NR and NMN are precursor molecules that cells convert into NAD+, so taking them raises the available pool. In human blood that rise is reliable and dose-dependent, with NR at 1000 mg a day more than doubling whole-blood NAD+.
Swallowed as NR (1/7)
Nicotinamide riboside (NR), taken as a capsule, is a precursor the body turns into NAD+.
What that bump does downstream is the open question. In prediabetic women, NMN increased insulin-stimulated glucose disposal and muscle insulin signaling and switched on genes tied to muscle remodeling. In healthy older adults, NMN raised blood NAD and shortened a 4-meter walk time but did not change a stepping test. Pooled trials find no effect on fasting glucose, HbA1c, lipids, body weight, or muscle mass, so the biomarker moves while most outcomes do not.
NR and NMN are sold as capsules for energy, aging, metabolism, and exercise recovery, and NAD+ itself is sold as an injectable or intravenous infusion by clinics. In trials, 100, 300, and 1000 mg of NR a day raised whole-blood NAD+ by 22%, 51%, and 142% within 2 weeks in overweight adults, and 250 to 900 mg of NMN a day raised blood NAD in middle-aged and older adults. In postmenopausal women with prediabetes, 10 weeks of NMN increased muscle insulin sensitivity measured by clamp. In 80 healthy middle-aged adults, NMN modestly lengthened six-minute walking distance.
As dietary supplements in the United States they reach the market without FDA review of safety or effectiveness, and NR has a generally recognized as safe notice for use in foods. Trials have used doses from 250 to 2000 mg a day for 14 days to 24 weeks. Injectable and intravenous NAD+ products are a different matter: Health Canada lists NAD+ among unauthorized injectable products it has seized, and no randomized trial supports infusions. Nothing has been shown to extend human lifespan.
The human evidence is unusually good for a supplement and unusually modest in what it shows. Randomized trials establish that NR and NMN raise blood NAD+ within weeks, and a 6-week crossover trial in middle-aged adults, an 8-week dose-ranging trial, and a 60-day four-arm NMN trial all agree. Functional signals are scattered: better muscle insulin sensitivity in prediabetic women, longer walking distance in 80 healthy adults, faster 4-meter walks and better sleep scores in 60 older adults. Meta-analyses of eight to fifteen trials find no benefit for glucose control, lipids, or muscle mass and function.
The gap between biomarker and outcome is the whole story: raising NAD+ is proven, while preventing disease or slowing aging is not. Trials are short, mostly in healthy or mildly at-risk adults, and underpowered for hard endpoints. Whether specific groups with low baseline NAD+ benefit more is untested. Injectable and intravenous NAD+ products have no randomized evidence at all.
Both supplements are well tolerated at studied doses. In an 8-week trial of NR up to 1000 mg a day there was no flushing and no difference in adverse events from placebo, and NR did not raise LDL cholesterol. A 2026 meta-analysis of fifteen NMN trials found no increase in overall, serious, or organ-specific adverse events and no rise in liver enzymes. Long-term safety beyond 24 weeks and the safety of injected or infused NAD+ have not been studied.
Supplements reach the market without FDA review of safety or effectiveness.
NR and NMN are sold in the United States as dietary supplements, a category the FDA does not review for safety or effectiveness before sale, and NR holds a generally recognized as safe status for use in foods. Neither is an approved drug for any condition. Injectable and intravenous NAD+ falls outside the supplement framework, and Health Canada lists NAD+ among unauthorized injectable products it has seized. Claims that these products treat disease or extend life are not supported by the trials that exist.