Covarrubias AJ, Perrone R, Grozio A, et al. (2021). NAD(+) metabolism and its roles in cellular processes during ageing. Nat Rev Mol Cell Biol, 22(2):119-141.
What is NAD+?
NAD+ (nicotinamide adenine dinucleotide) is a helper molecule found in every living cell. Your cells use it to turn food into energy, and many enzymes that repair DNA and control genes can’t work without it [1].
Your body builds NAD+ from scratch out of tryptophan, an amino acid found in food, and recycles it from several forms of vitamin B3 [2]. Two of those vitamin B3 forms, nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN), are sold as supplements to boost NAD+ levels [3].
Strictly speaking, NAD+ isn’t a peptide. It’s a coenzyme, built from two linked nucleotides rather than amino acids. We’ve included it because NAD+ drips have become popular in wellness clinics [4, 5].
How might it work?
- Powering your cells. NAD+ carries electrons from one chemical reaction to the next. That shuttle service sits at the heart of how cells make energy [1].
- Fueling repair enzymes. NAD+ is also consumed by enzymes that repair damaged DNA (PARPs) and by sirtuins, enzymes that help regulate genes [1]. Sirtuins are thought to help explain some of the health benefits of calorie restriction [6].
- Why levels might fall. In mice, an enzyme called CD38, which breaks NAD+ down, becomes more active with age and drives NAD+ levels down [7]. In human skin, especially in men, DNA-repair enzymes grow busier with age as NAD+ falls, suggesting that repairing more damage may use up more NAD+ [8].
- The “top up” idea. In old mice, raising NAD+ levels restored the cells’ energy factories (mitochondria) to a youthful state [9]. That finding helped spark today’s interest in NAD+ boosting.
What has research found?
Does NAD+ really fall with age?
- Several studies say yes. NAD+ levels were lower with age in human skin [8], in the brain as measured by scans [10], and in blood plasma [11].
- Activity seems to matter. NAD+ in muscle was lower in older adults, especially those with physical limitations. Older adults who exercised regularly had levels closer to those of young people, and NAD+ tracked with how many steps people took each day [12].
- Exercise can rebuild the machinery. Twelve weeks of aerobic or strength training raised the main enzyme muscles use to recycle NAD+ by 12% to 30%, reversing its decline with age [13].
- But not every study agrees. A 2026 analysis of seven groups of people found that NAD+ in whole blood stayed steady with age [14]. A 2025 review noted that an age-related decline has been seen consistently in only a limited number of human studies [15].
In animals
- Healthier aging: Mice given NMN by mouth for a year gained less weight with age, were more active, had better insulin sensitivity and blood fats, and kept better eye function, with no obvious toxicity [16].
- Stem cells and lifespan: NR rejuvenated muscle stem cells in old mice and extended their lifespan [17].
- A surprising twist: Mice whose muscles had 85% less NAD+ than normal still had healthy muscles, normal strength and exercise capacity, and no sign of faster muscle aging [18]. That suggests low NAD+ may not be what drives muscle aging.
In people: NAD+ drips and injections
- What happens to infused NAD+? In the first study to track an IV drip of NAD+ in people, blood NAD+ levels didn’t rise at all for the first two hours. The body cleared it as fast as it arrived and broke it down into smaller pieces [19].
- Heart failure: In a trial of 180 people with heart failure in China, adding a small daily dose of IV NAD+ (10 mg a day for 7 days) to standard treatment led to stronger heart pumping at one month (an ejection fraction of about 45%, compared with 42% on placebo). There were hints of fewer hospital stays, but those weren’t statistically certain [20].
- Addiction recovery: In an uncontrolled report of 50 people with substance use disorder, infusions combining NAD+ with other ingredients were followed by lower cravings, anxiety, and depression. There was no comparison group, and the lead author holds patents on part of the treatment [21].
- Anti-aging and wellness: A 2026 systematic review found no trials that measured health outcomes from IV or intramuscular NAD+ for anti-aging or wellness [22].
In people: oral NAD+ boosters (NR and NMN)
- They reliably raise NAD+. In one trial, NR raised blood NAD+ by 22%, 51%, and 142% at increasing doses within two weeks [23]. At higher doses, blood NAD+ rose up to fivefold [24].
- Promising results:
- NMN improved how well muscles respond to insulin in postmenopausal women with prediabetes [25].
- In 90 people with poor leg circulation (peripheral artery disease), six months of NR improved the distance walked in six minutes: up 7 meters, compared with down 10.6 meters on placebo [26].
- In people with COPD, six weeks of NR cut a marker of airway inflammation by about half, and the effect lasted 12 weeks after treatment stopped [27].
- In people newly diagnosed with Parkinson’s disease, NR raised NAD+ in the brain. Those whose brain levels rose showed changes in brain metabolism and mild improvement in symptoms [28].
- Results that fell flat:
- In obese men, 12 weeks of NR didn’t improve insulin sensitivity or body composition [29].
- A 2025 meta-analysis found no evidence that NR or NMN preserves muscle mass or function in adults over 60 [30].
- A 2026 meta-analysis of 15 NMN trials found no clear effect on weight, blood sugar, or cholesterol [31].
How strong is the evidence?
| What we know so far | What we still don’t know |
|---|---|
| NAD+ is essential to energy and repair in every cell [1] | Whether NAD+ drips or injections slow aging or improve wellness, because no trials have measured it [22] |
| Oral NR and NMN reliably raise NAD+ levels [22, 23] | What happens to infused NAD+ in the body, because only small studies have tracked it [4, 19] |
| Boosting NAD+ helps aging mice in many ways [16, 17] | Whether NAD+ truly declines with age in people, because studies disagree [14, 15] |
| A few human trials show promise in specific conditions [25, 26, 27] | Long-term safety, including the effect on existing cancers [2, 3] |
A few more things to keep in mind:
- Raising NAD+ is easy; proving benefits is harder. Oral boosters reliably raise NAD+, but their effects on health outcomes have been mixed and often null [22].
- Mice aren’t people. Results from rodents don’t translate straightforwardly to humans [15].
- Industry ties are common. Several trials were funded or co-authored by companies that sell NAD+ products or infusions [5, 23, 27].
Safety: what we know
- Oral boosters seem well tolerated in the short term. NR at 3,000 mg a day for four weeks caused no moderate or severe side effects in people with Parkinson’s disease [24]. In NMN trials lasting up to 24 weeks, side effects were no more common than with placebo [31].
- Drips can be uncomfortable. At a wellness clinic, people receiving 500 mg NAD+ drips reported moderate to severe stomach symptoms, a faster heart rate, and chest pressure. The symptoms made the drips take longer, about 97 minutes on average versus 37 minutes for NR drips, and they went away once the drips ended [5]. Nausea, cramping, and flushing have also been reported [4].
- No long-term data. Long-term safety data for IV NAD+ are lacking [4].
- The cancer question. NAD+ boosters might help cancer cells as well as healthy ones. In a mouse model of an aggressive breast cancer, NR made the cancer more common and more likely to spread to the brain [32]. In other mouse studies, NMN helped pancreatic tumors grow and resist chemotherapy [3]. Researchers urge caution for people with active cancer [3].
Legal status
- Not an approved medicine. NAD+ isn’t an FDA-approved drug [S1, S2].
- United States: FDA lists NAD+ as “under evaluation” for compounding, and it doesn’t intend to act against pharmacies that compound with substances in that group, as long as certain conditions are met [S1, S2]. FDA proposed in 2019 not to add NAD+ to its approved list of compounding ingredients, but it hasn’t made a final decision [S2, S3].
- Supplements: NR and NMN are sold as dietary supplements [23, 31].
- Sports: NAD+ itself isn’t named on the World Anti-Doping Agency’s 2026 banned list. However, IV drips or injections totaling more than 100 mL in 12 hours are banned at all times, except during hospital treatment, surgery, or medical tests. That means an NAD+ drip can break the rules even though NAD+ itself doesn’t [S4].
The bottom line
NAD+ sits at the center of how our cells make energy and repair themselves, and boosting it has produced striking results in aging mice. Oral boosters reliably raise NAD+ in people, and early trials have shown encouraging signals in heart failure, poor circulation, lung disease, and Parkinson’s disease.
Still, the big promises haven’t been proven. It isn’t even settled whether NAD+ falls with age in people, and the popular IV drips have barely been studied. Larger, longer trials, especially of drips and injections, are the next step toward finding out how much NAD+ boosting can really do for human health.