Does NAD+ Slow Aging? What Human Trials of NMN and NR Actually Show

NAD+ boosters, nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN), are sold as anti-aging supplements, and IV NAD+ drips are marketed for longevity. Do they slow aging in people? A 2026 systematic review of 33 human intervention studies found that oral NR and NMN reliably raise NAD+ levels in the blood and are generally well tolerated. But their effects on the things that matter for aging, such as muscle, metabolism, blood vessels and function, “were heterogeneous and often null or endpoint-specific.” The review found no outcome trials of IV NAD+ for anti-aging.^[1] Here is what the human trials actually show.

The short answer

• They raise NAD+. NR and NMN increase blood NAD+ in middle-aged and older adults, and NR reaches aging muscle.^[2][3][4]
• Aging outcomes are mostly null. NMN didn't improve muscle mass, grip strength or gait speed in a meta-analysis of older adults.^[9] NR didn't improve cognition in mild cognitive impairment,^[6] and adding it to exercise didn't lower blood pressure more than exercise alone.^[7]
• A few small positive signals. A slight drop in diastolic blood pressure with NMN (about 2 mmHg),^[11] and better arterial stiffness in a rare premature-aging syndrome.^[8]
• Short-term safety looks fine. NMN didn't increase adverse events in trials lasting up to 24 weeks.^[10] Long-term effects are unknown.

The idea behind NAD+ boosters

NAD+ is a coenzyme used in energy metabolism and DNA repair. In animal studies its levels decline with age, and raising them improved many measures of aging. The 2026 review found that in rodents, NAD+ augmentation “was frequently associated with improvements in metabolic, mitochondrial, inflammatory, and functional outcomes,” though results varied.^[1] The question is whether that carries over to people.

Do the supplements raise NAD+ in people? Yes

This part is well established. In a randomized crossover trial in healthy middle-aged and older adults, six weeks of NR was “well tolerated and effectively stimulates NAD+ metabolism.”^[2] In 12 older men, NR for 21 days “elevated the muscle NAD+ metabolome” and lowered some inflammatory cytokines, but did not change mitochondrial energy production in muscle.^[3] In healthy older men, NMN at 250 mg a day raised blood NAD+.^[4] A 2026 head-to-head study found NR and NMN raised blood NAD+ comparably over 14 days, possibly working partly through gut bacteria.^[12]

Do they slow aging? What the outcome trials found

Muscle and physical function

A 2025 meta-analysis in older adults found NMN had “no significant effects” on skeletal muscle mass, handgrip strength, gait speed or the five-times sit-to-stand test, and did not improve knee strength or overall physical performance. NR lengthened walking distance in people with peripheral artery disease, but people with mild cognitive impairment did slightly worse on two function tests.^[9] An earlier trial in older men reported only “nominally significant” improvements in gait speed and grip that “should be validated in larger studies.”^[4]

Brain and cognition

In a 2026 pilot trial in 42 older adults with amnestic mild cognitive impairment, NR doubled blood NAD+ but produced “no improvements in cognitive function (primary outcome), total CBF, or blood pressure.” An exploratory analysis hinted at more blood flow in the hippocampus.^[6]

Blood pressure and blood vessels

The 2018 NR trial suggested future studies should look at blood pressure and arterial stiffness.^[2] Results since then are modest. A 2026 meta-analysis of 10 NMN trials found diastolic pressure fell by 2.15 mmHg, with no significant overall change in systolic pressure, though systolic pressure fell by 3.94 mmHg in people aged 60 and over.^[11] In a 2025 trial in adults 55 and over with high blood pressure, NR plus exercise did not lower daytime systolic pressure more than exercise plus placebo.^[7]

Metabolism

The best-known positive result is that 10 weeks of NMN increased muscle insulin sensitivity in postmenopausal women with prediabetes and overweight or obesity.^[5] But a 2026 meta-analysis of 15 NMN trials found “no significant effects” on body weight, BMI, fasting glucose, HbA1c, lipids or systolic blood pressure.^[10]

A rare premature-aging disease

The clearest benefit came in Werner syndrome, a rare inherited disease that causes accelerated aging. In a crossover trial with 26 weeks on each treatment (52 weeks in total), NR at 1,000 mg a day improved arterial stiffness and reduced skin ulcer area, with no serious adverse events.^[8] This is a disease with known NAD+ depletion, so it doesn't tell us whether NR slows normal aging.

What about IV NAD+ drips?

The 2026 systematic review found “no eligible outcomes trials evaluated intravenous or intramuscular NAD⁺ itself for anti-aging or wellness indications.”^[1] Whatever the clinic marketing says, there is no controlled human evidence that IV NAD+ slows aging. For cost and what drips actually deliver, see are NAD+ IV drips worth it?

Is it safe?

In the short term, it appears so. A 2026 meta-analysis of NMN trials at 250–2,000 mg a day for 14 days to 24 weeks found NMN “did not increase overall, serious, withdrawal-related, or system-specific adverse events, nor did it significantly elevate ALT or AST” liver enzymes.^[10] There are no long-term safety data in healthy people.

How NAD+ compares with GLP-1 drugs for longevity

The contrast is stark. Semaglutide has large randomized trials showing about 20% fewer deaths from any cause in people at high risk. See semaglutide and longevity. NAD+ precursors have no trial measuring survival, only small studies of biomarkers and function, most of them null. For the wider landscape, see our metabolic longevity drugs and supplements overview.

Bottom line

NR and NMN do what they claim at the biochemical level: they raise NAD+ in the blood and muscle. But across dozens of human studies, that hasn't translated into measurably slower aging. Muscle, cognition, blood pressure and metabolism mostly didn't improve, with small exceptions. They appear safe in the short term. If you take them, take them as an unproven experiment, not as a longevity treatment.