NAD+ has become one of the biggest talking points in longevity science, but the biology is easier to understand than much of the marketing makes it sound.

Short for nicotinamide adenine dinucleotide, NAD+ is a molecule found throughout the body. Your cells need it to make energy, manage metabolic reactions, and support enzymes involved in DNA repair and cellular signaling. (1)

That makes NAD+ important. It does not mean that simply raising NAD+ will make you younger, give you more energy, or extend your life. Human research is still working out where those benefits begin and end. (2)

Key Takeaways:

• NAD+ helps cells produce energy and supports processes linked to metabolism, DNA repair, and cellular stress responses. (1)

• NMN and NR can raise NAD-related biomarkers in humans, but health benefits across clinical trials have been mixed. (2)

• The common claim that NAD+ simply falls with age is more complicated than it sounds, especially when blood and individual tissues are compared. (3)

• Evidence for NAD+ injection benefits remains much thinner than the evidence for oral NAD+ precursors. (2)(7)

What Is NAD+?

NAD+ is a coenzyme, meaning it helps other enzymes carry out chemical reactions.

One of its main jobs involves transferring electrons during metabolism. NAD+ accepts electrons and becomes NADH. NADH can then help deliver those electrons to processes involved in producing ATP, the form of energy cells can use. (1)

Think of NAD+ and NADH as two versions of the same cellular courier, constantly switching back and forth as energy moves through the cell.

NAD+ also acts as a substrate for enzymes such as sirtuins and PARPs. These proteins take part in processes linked to metabolic regulation, cellular stress responses, and DNA damage repair. (1)

What Does NAD+ Do in the Body?

NAD+ has several well-established biological roles.

It helps:

• Convert carbohydrates, fats, and proteins into usable cellular energy

• Support mitochondrial metabolism

• Maintain normal redox reactions

• Supply NAD+-dependent enzymes such as sirtuins

• Support PARP enzymes involved in responses to DNA damage (1)

One distinction matters here. These are functions of NAD+ inside healthy cells, not proof that taking more NAD+ produces the same list of health benefits.

That gap between mechanism and clinical outcome is where many NAD+ discussions get ahead of the research.

Does NAD+ Decline With Age?

You may have seen claims that NAD+ drops sharply as soon as you hit your 30s or 40s. Human evidence is not that simple.

Some studies have found lower NAD+ concentrations with age in certain tissues, including skeletal muscle. Yet a 2025 review found that consistent evidence of age-related NAD+ decline in humans exists in only a limited number of studies. Researchers also noted major differences between tissues. (4)

Then came an interesting finding in 2026. Researchers measured whole-blood NAD+ across seven independent human cohorts and found that levels remained remarkably stable with age. The authors concluded that whole-blood NAD+ may not work well as a general biomarker of aging. (3)

That does not mean NAD+ metabolism stays unchanged everywhere in the body.

Instead, it suggests something more useful: NAD+ levels may behave differently in blood, muscle, liver, brain, and other tissues.

So claims that everyone loses a fixed percentage of NAD+ by a certain birthday deserve caution.

What Are the Potential Benefits of Increasing NAD+?

A 2026 systematic review examined 113 studies, including 33 human intervention studies. NAD+ precursors such as NMN and NR consistently raised NAD-related biomarkers, but changes in physical performance, metabolism, cardiovascular measures, and other health outcomes were mixed. (2)

Here is what human trials tell us so far.

Cellular Energy and Metabolism

Because NAD+ plays a central role in energy metabolism, raising NAD+ has attracted interest as a way to support mitochondrial function.

Human studies confirm that NAD+ precursors can increase NAD-related compounds in the blood. What we do not yet have is strong evidence that higher blood NAD+ reliably translates into noticeably more energy in healthy people. (2)

That is an important difference. A better biomarker does not automatically mean you will feel different.

Metabolic Health

One frequently cited human trial involved postmenopausal women with prediabetes.

Participants took 250 mg of NMN daily for 10 weeks. NMN increased NAD-related metabolites and improved skeletal muscle insulin sensitivity compared with placebo. However, several other metabolic outcomes did not significantly change. (5)

The result is promising, especially because insulin sensitivity matters for metabolic health.

Still, the trial studied a specific group of women with prediabetes. It cannot tell us that NMN produces the same benefit in everyone.

Muscle Function and Physical Performance

A randomized trial in older men tested 250 mg of NMN per day for up to 12 weeks.

Blood NAD+ and related metabolites increased. Researchers also reported modest signals involving walking speed and one grip-strength measurement, although they noted that larger studies are needed to confirm those findings. Body composition did not significantly improve. (6)

Another randomized study followed 60 older adults taking 250 mg of NMN daily for 12 weeks.

NMN raised blood NAD+ and shortened 4-meter walking time compared with placebo. However, the study's primary physical-performance outcome, a stepping test, did not significantly improve. (8)

That mixed pattern comes up repeatedly in NAD+ research. Biomarkers respond quite reliably. Functional benefits are much less consistent.

Healthy Aging and Cellular Repair

NAD+ sits at the intersection of several biological pathways researchers study in aging, including mitochondrial metabolism, sirtuins, PARPs, and cellular stress responses. (1)

This makes NAD+ scientifically interesting for healthy aging. What has not been demonstrated in humans is just as important.

Clinical trials have not shown that increasing NAD+ reverses aging, extends human lifespan, or produces broad rejuvenation. A recent systematic review found encouraging signals in some areas, but clinical outcomes remained inconsistent. (2)

So the strongest case for NAD+ right now comes from its biology and early human research, not from proof that it slows human aging.

NAD+ vs. NMN vs. NR

These terms get mixed together, but they are different molecules.

This distinction matters when looking at research. Most human trials aimed at increasing NAD+ have tested NMN or NR, not direct oral NAD+. (2)(4)

So when you see a headline saying researchers found a “benefit of NAD+,” check what participants were given. In many cases, the study used a precursor instead.

What Are the Benefits of NAD+ Injections?

NAD+ injections and IV infusions have become popular at longevity clinics, where they may be promoted for energy, mental clarity, recovery, or healthy aging.

The clinical evidence does not yet support such a broad list of benefits.

A 2026 retrospective pilot study looked at people receiving 500 mg of IV NAD+ for four consecutive days and compared them with people receiving IV nicotinamide riboside. The study focused mainly on tolerability, infusion time, safety markers, and metabolic measurements. (7)

People receiving IV NAD+ reported symptoms including nausea, abdominal discomfort, increased heart rate, and chest pressure during infusions. (7)

More importantly, the study was not designed to show that NAD+ IV therapy slows aging or improves long-term health.

The 2026 systematic review also found no eligible human clinical outcome trials of intravenous or intramuscular NAD+ itself for anti-aging or wellness purposes. (2)

That does not prove NAD+ injections have no benefit. It means the claims have moved faster than the clinical evidence.

Can You Increase NAD+ Levels?

The body can make NAD+ through several pathways using vitamin B3-related compounds.

Among the best-known NAD+ precursors are:

• Nicotinamide mononucleotide, or NMN

• Nicotinamide riboside, or NR

• Nicotinamide

• Nicotinic acid

NMN and NR have received the most attention in newer longevity research.

Human trials show that both can raise NAD-related biomarkers, although researchers are still studying how much of that increase reaches different tissues and what health effects follow. (2)(4)

This tissue question matters more than it might seem. Higher NAD+ in blood does not necessarily tell us what happened inside muscle, brain, liver, or other organs. (3)(4)

What Does the Research Say About NAD+ So Far?

NAD+ is not just another wellness trend. It is a molecule your cells genuinely depend on. The unanswered question is what happens when we deliberately increase it.

So far, the evidence gives us a fairly clear middle ground. NMN and NR can raise NAD-related biomarkers in humans. Some trials have found encouraging changes in insulin sensitivity, walking performance, or other measures, while others have found little or no meaningful effect. (2)(5)(6)(8)

Direct NAD+ injections have much less clinical evidence behind them. (2)(7)

That makes NAD+ research worth watching, but it is still too early to treat higher NAD+ as a shortcut to slower aging.

At Omre, we take the same evidence-first approach with our NMN + Resveratrol formula, using research-backed ingredients for people who want to support healthy aging without turning early science into exaggerated promises.

FAQs

What does NAD+ do for your body?

NAD+ helps cells carry out energy-producing reactions and supports enzymes involved in metabolism, DNA damage responses, and cellular signaling. (1)

What is the difference between NAD and NAD+?

NAD refers to nicotinamide adenine dinucleotide in general. NAD+ is its oxidized form, while NADH is the reduced form that carries electrons during metabolic reactions. (1)

Does NAD+ decline with age?

Some human tissues show age-related declines in NAD+, but the evidence varies by tissue. A 2026 analysis found that whole-blood NAD+ remained stable across seven human cohorts, so blood NAD+ may not reflect aging throughout the body. (3)(4)

What are the benefits of NAD+ injections?

NAD+ injections are marketed for energy, recovery, cognition, and healthy aging, but strong human evidence for these benefits is lacking. Existing IV research has focused more on tolerability and biomarkers than proven long-term health outcomes. (2)(7)

Is NMN the same as NAD+?

No. NMN is a precursor that enters the body's NAD+ production pathway. Human trials show that taking NMN can increase NAD-related metabolites, including blood NAD+. (5)(6)

References

1. NAD+ Metabolism: Pathophysiologic Mechanisms and Therapeutic Potential

2. NAD+ Supplementation for Anti-Aging and Wellness: A PRISMA-Guided Systematic Review of Preclinical and Clinical Evidence

3. Human Whole-Blood NAD+ Levels Do Not Vary With Age or Lifestyle Interventions

4. NAD+ Precursor Supplementation in Human Aging: Clinical Evidence and Challenges

5. Nicotinamide Mononucleotide Increases Muscle Insulin Sensitivity in Prediabetic Women

6. Chronic Nicotinamide Mononucleotide Supplementation Elevates Blood NAD+ Levels and Alters Muscle Function in Healthy Older Men

7. Intravenous Infusion of NAD+ Versus Nicotinamide Riboside: A Retrospective Tolerability Pilot Study

8. NMN Increased Blood NAD Levels, Maintained Walking Speed, and Improved Sleep Quality in Older Adults