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What common assumptions about NAD+ hold up in studies?

Many assumptions about NAD+ are in circulation. This page sets three of them against human studies. Each section begins with the finding.

October 2026

Purpose: Information service and wording aid for the conversation with your own doctor. No detection, prognosis or treatment of diseases.

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What are the key points in brief?

Does NAD+ always help with fatigue?

Common assumption

A 2026 systematic review regards the clinical efficacy of NAD+ supplementation for anti-aging and wellness as unsettled1.

The review evaluated 113 studies, 33 of them in humans. Effects on function, metabolism and other health measures were mixed and often showed no difference1.

A study of 108 older adults examined sleep, fatigue and physical performance over twelve weeks. In one NMN group, sleepiness fell compared with baseline. The matching placebo group improved as well4.

Persistent fatigue can have many causes. In family practice, sleep disorders, depression and psychosocial strain are among the most common5. What can be checked medically is shown on the page What can lie behind fatigue before considering NAD+ infusions?.

According to a 2026 systematic review, the clinical benefit of NAD+ supplementation for anti-aging and wellness remains open1.

Does an NAD+ blood test show a deficiency?

Common assumption

According to a 2026 study, normal values of NAD and related compounds in human blood are so far not well known2.

In a group of 1,518 adults, the mean was 33.0 ± 5.5 µmol/L in whole blood6. The study does not state a reference range for interpreting single values.

The authors of a study with seven cohorts question the usefulness of the blood value as a marker of age or lifestyle3. The French National Academy of Medicine does not consider measuring biological age advisable for clinical practice on current knowledge7.

More on the page Can NAD+ be measured reliably in blood?.

As long as normal NAD+ values in human blood are not well known, a single measured value may hardly indicate a deficiency reliably2.

Does NAD+ fall with age in everyone?

Common assumption

In seven independent cohorts, whole-blood NAD+ stayed remarkably stable across age and under lifestyle interventions3.

In 299 healthy people aged 18 to 70, the blood value did not change with age2. In a group of 1,518 adults, the value fell with age only in men, according to the authors6.

These three studies of NAD+ and age measure NAD+ in blood. They make no statement about individual organs or tissues.

For human blood, a study with seven cohorts and a study of 299 healthy people show no fall in NAD+ with age3,2.

Which sources does this page rely on?

  1. Gallagher C, Emmanuel OO (2026). NAD⁺ supplementation for anti-aging and wellness: A PRISMA-guided systematic review of preclinical and clinical evidence. Ageing Research Reviews. DOI: 10.1016/j.arr.2026.103057

    The review asks what studies on NAD+ products show for ageing and well-being. It systematically assesses 113 studies, 33 of them in humans. NR and NMN may raise NAD levels and appear well tolerated, while a clinical benefit remains open, and suitable trials of NAD+ infusions were lacking.

  2. Euro L et al. (2026). Dynamics of blood NAD and glutathione in health, disease, aging, and under NAD+-booster treatment. Redox Biology. DOI: 10.1016/j.redox.2026.104343

    The study developed a standardised measurement of NAD and glutathione from a single whole-blood sample. It is a methods and cohort study with 299 healthy adults. Levels appeared stable with age and rose to a different extent from person to person under NAD+ boosters.

  3. Trętowicz MM et al. (2026). Human whole-blood NAD+ levels do not vary with age or lifestyle interventions. Nature Metabolism. DOI: 10.1038/s42255-026-01537-5

    The study tests whether whole-blood NAD+ changes with age or with lifestyle interventions. It used a validated mass spectrometry method in seven independent cohorts. Levels stayed largely stable and changed with nicotinamide riboside, which may call into question blood NAD+ as a marker of ageing.

  4. Kim M et al. (2022). Effect of 12-Week Intake of Nicotinamide Mononucleotide on Sleep Quality, Fatigue, and Physical Performance in Older Japanese Adults: A Randomized, Double-Blind Placebo-Controlled Study. Nutrients. DOI: 10.3390/nu14040755

    The study asks whether twelve weeks of NMN affect sleep, fatigue and physical performance in older people. It was randomised, double-blind and placebo-controlled with 108 older adults in Japan. Afternoon intake showed signs of better leg function and less drowsiness, while some values also improved with placebo.

  5. Maisel P, Baum E, Donner-Banzhoff N (2021). Fatigue as the Chief Complaint. Deutsches Ärzteblatt International. DOI: 10.3238/arztebl.m2021.0192

    The paper summarises how family doctors may assess persistent fatigue. It is a review based on a literature search. Its authors suggest that history, physical examination and simple laboratory tests may usually be enough, with further tests mainly when other findings point that way.

  6. Yang F et al. (2022). Association of Human Whole Blood NAD+ Contents With Aging. Frontiers in Endocrinology. DOI: 10.3389/fendo.2022.829658

    The study asks whether whole-blood NAD+ declines with age. It is a cross-sectional study of 1,518 adults from a community in China. A decline with age appeared only in men, which may point to differences between the sexes.

  7. Académie nationale de médecine (2026). Approche clinique de la longévité en bonne santé. Report of 13 January 2026, in French. www.academie-medecine.fr/wp-content/uploads/2026/01/RAPPORT-Approche-clinique-de-la-longevite-en-bonne-sante-APRES-VOTE.pdf

    The report asks what medical practice can do today to support a long and healthy life. It is a position paper of the French National Academy of Medicine. Based on current knowledge, it does not recommend measuring biological age or using anti-ageing agents in practice and gives priority to lifestyle.