What is NAD+ and why does it matter?

Updated November 3, 2026. For information only, not medical advice. This guide has no affiliate links.

NAD+ (nicotinamide adenine dinucleotide, sometimes written “NAD plus” or just “NAD”) is a helper molecule found in every cell. Your body uses it in everyday chemical reactions, including turning food into usable energy.

In a nutshell

• NAD+ is a molecule found in every cell. Your body uses it in everyday chemical reactions, including turning food into usable energy.
• Studies in animals link falling NAD+ levels to aging. In people the picture is less clear: a 2025 review says the evidence for an age-related drop in humans is limited, and a 2026 review says recent large-scale human data indicate whole-blood NAD+ does not fall with healthy aging per se.
• Supplements such as NMN and NR can raise NAD+ markers in the blood in human trials. So far, those trials have not shown clear health or fitness benefits.
• Evidence rating for “NAD+ supplements improve how people function”: Early (small or short human trials only). More on our rating scale below.

What is NAD+?

Basis: Google autocomplete (Nov 1, 2026); PMIDs 33353981 and 41540253.

NAD+ (short for nicotinamide adenine dinucleotide) is a helper molecule, or “coenzyme”. A 2021 review in Nature Reviews Molecular Cell Biology describes it as central to energy metabolism and also needed by other enzymes involved in things like DNA repair and immune-cell function.

You do not need to think of it as a “longevity” molecule to see why it matters: without it, cells cannot run their basic chemistry. Your body builds it from vitamin B3 and related ingredients. A 2026 study in Nature Metabolism describes NAD as a vitamin B3-derived molecule.

What is NAD+ used for, and what is it good for?

Basis: Google autocomplete (Nov 1, 2026); PMIDs 33353981, 41540253, 40275690.

Inside the body, NAD+ is used as a coenzyme in energy metabolism and by other enzymes, as described above. That is a statement about what the molecule does, not a claim that taking more of it helps you. When people search for what NAD+ is “good for”, they usually mean NAD+ supplements, and the human trials so far show that precursors raise NAD+ markers in blood but have not shown clear gains in how people function. The sections below go through that evidence.

Does NAD+ really fall as we get older?

Basis: PMIDs 33353981, 41083806 and 42787547.

You will often read that NAD+ declines with age. The same 2021 review says NAD+ levels fall gradually in tissues in multiple model organisms, “including rodents and humans”, but it also says much remains to be learned about whether topping NAD+ back up helps aging humans. (Some of that review’s authors disclose links to NAD-related companies.)

A more recent 2025 review in Nature Metabolism is more cautious. It says an age-related fall in human NAD+ has been “consistently observed only in a limited number of studies”. It also says data on NAD+ in human tissues “remains sparse” and that results from rodents cannot simply be carried across to people. That review reported no competing interests.

A 2026 narrative review in Frontiers in Aging goes a step further. It says recent large-scale human data indicate that whole-blood NAD+ concentrations do not decline with healthy aging per se. We have not opened the underlying studies it refers to, so treat this as that review’s reading of the data. One of its four authors discloses being employed by a healthcare company.

In plain terms: the idea that NAD+ falls with age is well supported in animals and unsettled in people. Our rating for “NAD+ falls with age in humans” is Mixed.

Can supplements raise NAD+?

Most supplements sold for NAD+ do not contain NAD+ itself. They contain a “precursor”, an ingredient the body can convert into NAD+. According to the 2026 Nature Metabolism study, the most prominent precursors are nicotinamide (a form of vitamin B3), nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN). Our guide to NMN vs NR compares the last two.

In human trials, these do raise NAD+ markers:

• NR: in a 6-week-per-arm crossover trial, 24 healthy middle-aged and older adults took 1,000 mg a day. Their NAD+ in blood cells was about 60% higher than on placebo, according to the full paper.
• NMN: in a 10-week trial, 25 postmenopausal women with prediabetes finished the study (13 on NMN, 12 on placebo) and took 250 mg a day. Blood-cell NAD+ rose, according to the full text.
• NR and NMN side by side: in a 14-day study of 65 healthy adults, both NR and NMN (1,000 mg a day each) raised circulating NAD+ by a similar amount compared with placebo. It was open-label (people knew what they were taking), and most of the authors work for Nestlé.
• NMN at a high dose: a September 2026 trial in npj Aging gave adults aged 65 and over 1,250 mg a day for 24 weeks. Blood NAD+ and related substances rose significantly. Read our news report on it.

Does a higher NAD+ level mean better health?

Basis: PMIDs 40275690 and 42848371; the npj Aging 2026 trial (DOI 10.1038/s41514-026-00482-7).

Not so far. A higher number on a blood test is not the same as feeling or functioning better.

• In the 1,250 mg NMN trial above, there was no significant improvement in the main outcome (hearing) or in physical performance. The authors said broader benefit “remains limited”. The company that makes the NMN funded the study, and three authors are its employees.
• A 2025 meta-analysis pooled randomized trials of NMN and NR in adults with an average age over 60. It concluded the evidence “does not support” using them to preserve muscle mass or function.
• The big NOPARK trial gave 500 mg of NR twice a day for 52 weeks to 410 people with early Parkinson’s disease. Their symptom scores did not improve, and the NR group scored worse than the placebo group (by 2.72 points on a 0 to 236 scale). That was a trial in people with a particular condition, so it says little about healthy adults. We cover it in our news report.
• Some trials have shown positive signals. In the NMN prediabetes trial, muscle insulin sensitivity improved, though fasting blood sugar did not change, and it was a small study (25 women).

Many of the strongest claims about NAD+ come from animal studies, and the 2025 review above warns that rodent results cannot simply be carried across to people. Human results are much more modest.

How can I increase NAD+ naturally?

We did not find a trial showing that any food or habit reliably “boosts NAD+” in people. Here is what we can say from sources we have checked:

• Food: the UK’s NHS says vitamin B3 (niacin) is found in meat, fish, wheat flour and eggs, and that you should be able to get all you need from a varied, balanced diet. It lists about 16.5 mg a day for men and 13.2 mg for women. The US NIH Office of Dietary Supplements gives slightly different figures: 16 mg of niacin equivalents (NE) a day for men and 14 mg NE for women aged 19 and over. It says most people in the US get enough from food, and that niacin is found in poultry, beef, pork, fish, some nuts, legumes and grains, and fortified breads and cereals.
• Exercise: a 2023 meta-analysis of five studies found that exercise training increased muscle levels of an enzyme (iNAMPT) that helps the body make NAD+. That is not the same as showing NAD+ itself rose, so treat it as an interesting lead rather than proof.

The NHS also gives general advice on physical activity and eating well. The WHO also gives global advice on physical activity and healthy eating. Our beginner’s guide to longevity supplements covers these basics first.

Are NAD+ supplements safe?

In the short trials above, NMN and NR were generally well tolerated. The authors of the 2026 high-dose NMN trial still say careful safety monitoring is warranted. Long-term safety in healthy people has not been established in the trials we read.

One note on vitamin B3: the UK’s NHS says high doses of nicotinic acid supplements can cause skin flushing, and that there is not enough evidence to know the effects of high daily doses of nicotinamide supplements. The NIH Office of Dietary Supplements says supplements with 30 mg or more of nicotinic acid can cause skin flushing, and that nicotinamide at 500 mg a day or more can cause diarrhea and easy bruising. Check with a doctor or pharmacist first if you take medication or have a health condition.

NAD+ injections and IV drips: a short answer

Basis: PMIDs 41655607 and 42787547.

Some clinics give NAD+ itself by injection or intravenous (IV) drip, which is a different thing from taking NMN or NR by mouth. A 2026 systematic review found no outcome trials of IV or intramuscular NAD+ for anti-aging or wellness, and a 2026 narrative review called the human evidence sparse and preliminary. We do not recommend or compare clinics or list prices. Our full explainer is NAD+ injections: what they are and what the evidence says.

FAQ

What is NAD+ used for?

In the body, NAD+ is a coenzyme used in energy metabolism and by enzymes involved in DNA repair and immune-cell function. As a supplement target, NAD+ precursors raise NAD+ markers in blood in human trials, but the trials we cite have not shown clear gains in function. Using NAD+ supplements for health goals is not proven.

Basis: Google autocomplete (Nov 1, 2026); PMIDs 33353981, 40275690.

What is NAD+ good for?

NAD+ is essential to every cell’s basic chemistry, so you cannot do without it. Whether extra NAD+, or a precursor, is good for you is a different question. In human trials of NMN and NR, blood NAD+ goes up, but clear improvements in hearing, muscle or fitness have not been shown in the trials we read.

Basis: Google autocomplete (Nov 1, 2026); PMIDs 33353981, 40275690, 41540253.

What is an NAD+ supplement?

Most products sold for NAD+ contain a precursor the body can convert into NAD+, such as nicotinamide riboside (NR), nicotinamide mononucleotide (NMN) or nicotinamide, rather than NAD+ itself. The 2026 Nature Metabolism study calls these the most prominent NAD+ “boosters”. Availability varies by country; check local rules before buying. For the US side, see is NMN FDA approved?

Basis: Google autocomplete (Nov 1, 2026); PMID 41540253.

What are NAD+ injections?

NAD+ injections and IV drips give NAD+ itself, usually in a clinic. A 2026 systematic review found no outcome trials of IV or intramuscular NAD+ for anti-aging or wellness, and a 2026 review reported nausea, cramping, flushing and chest discomfort in the sparse human data. See our NAD+ injections guide before deciding anything.

Basis: Google autocomplete (Nov 1, 2026); PMIDs 41655607, 42787547.

Is NAD+ the same as NMN or NR?

No. NAD+ is the molecule your cells use. NMN and NR are precursors, different starting ingredients the body can turn into NAD+. In a 14-day trial of 65 healthy adults, NR and NMN raised circulating NAD+ by a similar amount. Our NMN vs NR guide compares them in detail.

Basis: Google autocomplete (Nov 1, 2026); PMID 41540253.

What this means for you

What this means for you

• What NAD+ is: a molecule your cells use every day.
• What supplements do: NMN and NR raise NAD+ markers in blood in human trials. That part is fairly consistent.
• What they have not shown yet: clear improvements in hearing, fitness, muscle or other everyday measures in the trials we read.
• Injections and IV drips: we found no outcome trials of IV or intramuscular NAD+ for anti-aging or wellness (see our NAD+ injections guide).
• Doses studied: 250 mg a day (NMN, 10 weeks), 1,000 mg a day (NR, 6 weeks), 1,250 mg a day (NMN, 24 weeks), 1,000 mg a day (both, 14 days). These describe the studies, not advice.
• Evidence rating:
  • NAD+ supplements raise NAD+ markers in humans: Good
  • NAD+ supplements improve function or health in humans: Early
  • NAD+ falls with age in humans: Mixed
  • NAD+ benefits seen in animals: Very early (animal research)

How we rate the evidence

We use five plain labels across this site: Strong (consistent benefit across large trials or reviews), Good (benefit for specific outcomes in several trials, with gaps), Mixed (mixed results, or benefit only in some groups), Early (small or short human trials only) and Very early (animal or lab research only).

Keep reading

• NMN vs NR: what’s the difference?
• NAD+ injections: what they are and what the evidence says
• Longevity supplements for beginners: where to start
• Our beginner’s guide to NMN and to NR
• If you are interested in NAD+ supplements, see our best NAD+ supplement page. It may carry affiliate links, with a disclosure above the first link (affiliate disclosure).

Sources

Pages were opened on November 1, 2026, unless a different date is given.

1. Covarrubias AJ et al. NAD+ metabolism and its roles in cellular processes during ageing. Nat Rev Mol Cell Biol 2021. PubMed
2. Vinten KT et al. NAD+ precursor supplementation in human ageing: clinical evidence and challenges. Nat Metab 2025. PubMed
3. Christen S et al. The differential impact of three different NAD+ boosters on circulatory NAD and microbial metabolism in humans. Nat Metab 2026. PubMed
4. Martens CR et al. Chronic nicotinamide riboside supplementation is well-tolerated and elevates NAD+ in healthy middle-aged and older adults. Nat Commun 2018. PubMed · full text
5. Yoshino M et al. Nicotinamide mononucleotide increases muscle insulin sensitivity in prediabetic women. Science 2021. PubMed · PMC full text
6. Sustained NAD+ augmentation by high-dose nicotinamide mononucleotide supplementation in older adults: a 24-week randomized, double-blind, placebo-controlled trial. npj Aging, September 25, 2026. DOI
7. Prokopidis K et al. The effect of nicotinamide mononucleotide and riboside on skeletal muscle mass and function: a systematic review and meta-analysis. J Cachexia Sarcopenia Muscle 2025. PubMed
8. Brakedal B et al. Nicotinamide riboside for patients with early-stage Parkinson disease: the NOPARK randomized clinical trial. JAMA, October 8, 2026. PubMed
9. Sun X et al. Exercise training upregulates intracellular nicotinamide phosphoribosyltransferase expression in humans: a systematic review with meta-analysis. Front Public Health 2023. PubMed
10. NHS (UK). Vitamin B (page last reviewed August 3, 2020), Physical activity guidelines for adults aged 19 to 64 (last reviewed May 22, 2024) and 8 tips for healthy eating (last reviewed November 22, 2022).
11. NIH Office of Dietary Supplements (US). Niacin: Fact Sheet for Consumers (updated March 22, 2021).
12. World Health Organization. Physical activity fact sheet (June 26, 2024); Healthy diet fact sheet.
13. Alangari A et al. Narrative review of intravenous NAD+ and NAD+ precursors in wellness and translational medicine. Front Aging 2026. PubMed (opened November 3, 2026)
14. Gallagher C, Emmanuel OO. NAD⁺ supplementation for anti-aging and wellness: a PRISMA-guided systematic review of preclinical and clinical evidence. Ageing Res Rev, April 2026. PubMed (opened November 3, 2026)

This article is for information only and is not medical advice. Speak to a healthcare professional before changing medication or supplements.