Nicotinamide Riboside, NMN and Other Niacin Precursors: What Is and Is Not Known
What nicotinamide riboside (NR) and NMN are, what small human trials found so far, what they have not shown, and why safety over the long term is still unknown.
Content last updated . This page has not been medically reviewed.
Quick answer
Nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN) are marketed as "NAD+ boosters". They are sold alongside niacin (vitamin B3) products, but they are not the same thing as niacin, and they are not an established vitamin. In the human trials we read, they raised markers in the blood, were generally well tolerated over weeks to months, and did not show clear health benefits. Long-term safety and benefits are not known.
Evidence labels used on this page: promising but limited, insufficient evidence, preclinical, marketing claim. Trial amounts are study amounts, not advice. Biomarker change (such as a higher NAD+ level in blood) is kept separate from clinical outcomes (such as symptoms, disease or survival).
What these terms mean
NAD+ is a molecule found in cells that takes part in energy metabolism, DNA repair and gene expression. [1] NR and NMN are "precursors": substances the body can use to make NAD+. [2] Niacin itself, in its two food forms nicotinic acid and nicotinamide, is a recognized nutrient with intake levels set by official bodies. [3] NR and NMN do not appear on the NHS or MedlinePlus B-vitamin pages we read. [3] [4]For the wider longevity picture, which this page does not duplicate, see NAD, NMN and longevity claims, NAD, NMN and nicotinamide riboside and NMN human evidence.
What human trials found
| Trial or review | Who and how long | What it found | Strength |
|---|---|---|---|
| NR in healthy adults (2018) | Healthy middle-aged and older adults; two 6-week periods, randomized, placebo-controlled crossover. | NR was well tolerated and increased NAD+ metabolism. The authors suggested future trials should look at blood pressure and arterial stiffness. [5] | Biomarker change; promising but limited |
| NR in mild cognitive impairment (2024) | 20 older adults; up to 1 g a day for 10 weeks; pilot. | Blood NAD+ rose 2.6-fold with no between-group difference in adverse events. Memory and thinking scores stayed stable. [6] | Safety pilot; no cognitive benefit shown |
| NR in Parkinson's disease (2022) | 30 newly diagnosed, untreated patients; 1,000 mg NR or placebo for 30 days; phase I. | Well tolerated; brain NAD levels rose by a variable amount, and in people whose brain NAD rose, changes in brain metabolism were associated with mild clinical improvement. Authors called for larger trials. Two authors filed a patent application on NR in Parkinson's. [7] | Phase I; insufficient evidence for benefit |
| NMN in prediabetes (2021) | Postmenopausal women with prediabetes who were overweight or obese; 10 weeks; placebo-controlled. | Increased muscle insulin sensitivity and insulin signaling. Some authors receive patent-licensing fees related to NMN. [8] | Mechanistic outcome; promising but limited |
| NMN safety review (2026) | 15 randomized trials; doses 250 to 2,000 mg a day; 14 days to 24 weeks. | No increase in adverse events or liver enzymes. Broad metabolic benefits were not evident; preliminary signals for blood pressure and insulin resistance need larger, longer trials. [2] | Short-term safety; insufficient evidence for benefit |
| NAD supplement review (2024) | 10 trials, 489 people, mixed conditions and products (NADH and precursors). | Generally tolerated; all studies reported some side effects such as muscle pain, fatigue, sleep disturbance and headaches, none serious. [1] | Low certainty |
What has not been shown
- Aging or lifespan in people: Proper evidence not found. The trials above lasted days to months and measured blood markers or small clinical outcomes. We searched PubMed for human trials and reviews of NR, NMN and NAD+ precursors and did not find trials showing longer life or slower aging.
- Energy or "youthful" claims: Marketing claim. None of the trials we read reported an effect on everyday energy as its main result.
- Long-term safety (years): Proper evidence not found. The longest trial period in the NMN review was 24 weeks. [2]
Official amounts and limits
No recommended intake or upper limit for NR or NMN appeared in the NHS, MedlinePlus, EFSA or Health Canada pages we read. The official niacin figures apply to niacin itself and do not carry over:| Body and year | Population and form | Amount |
|---|---|---|
| NHS, UK (2020) | Adults, nicotinic acid supplements / nicotinamide supplements | 17 mg or less / 500 mg or less a day unlikely to cause harm [3] |
| EFSA, EU (2002 opinion) | Adults, nicotinic acid / nicotinamide | Upper limits 10 mg / about 900 mg a day [9] |
| Health Canada DRI table (page dated 2025) | Adults 19 to 50, synthetic niacin from supplements | 35 mg a day (niacin equivalents) [10] |
The trial amounts above (250 to 2,000 mg a day) are study amounts. We did not read a source that sets them as safe for the public. The regulatory status of NR and NMN as supplements may differ by country; we did not verify it from a primary regulator page, so please check your own regulator's current position.
Related
Niacin profile · Niacin flush and safety · The eight B vitaminsFrequently asked questions
Is nicotinamide riboside a vitamin?
Not one of the eight B vitamins listed by MedlinePlus. [4] It is a precursor to NAD+, as is NMN. [2]
Does NMN or NR slow aging?
Proper evidence not found. We searched PubMed; the human trials we read were short and measured blood markers or small outcomes. [2]
Are they safe?
Short-term trials of weeks to months reported good tolerability. [2] [6] Long-term safety (years) was not studied in the trials we read.
Is NR the same as niacin or niacinamide?
No. NR, niacin (nicotinic acid) and niacinamide (nicotinamide) are different substances, and official niacin limits do not apply to NR. [9]
Who should avoid them?
Proper evidence not found in the sources read for who must avoid them. Ask a clinician if you are pregnant, breastfeeding, have a health condition or take medicines.
More details: evidence, limits and cautions
The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.
Safety, interactions and who should ask first
- Medicines and health conditions: Proper evidence not found on interactions in the sources read. Ask a pharmacist, and see medication interactions.
- Pregnancy, breastfeeding and children: Proper evidence not found. The trials above enrolled adults; talk to your midwife, doctor or pediatrician before any use. See pregnancy and breastfeeding.
- Cancer, kidney or liver conditions, and before surgery: Proper evidence not found; tell your care team about every supplement. See surgery and procedures and longevity safety: who should not experiment.
- Liver monitoring in trials: the NMN review measured ALT and AST and found no significant rise over short periods. [2]
- Product quality: amounts on labels may not match contents; see quality testing and certifications. Please do not stop or swap a prescribed medicine for any supplement.
References
- Gindri IM, et al. Evaluation of safety and effectiveness of NAD in different clinical conditions: a systematic review. Am J Physiol Endocrinol Metab 2024;326(4):E417-27. PMID 37971292. Read 2026-10-23.
- Yang W, et al. Safety and metabolism-related outcomes of oral nicotinamide mononucleotide supplementation in adults: a systematic review and meta-analysis. Nutrients 2026;18(14):2251. PMID 42514320. Read 2026-10-23.
- NHS (UK). Vitamins and minerals: B vitamins and folic acid. Page last reviewed 3 August 2020. Read 2026-10-23.
- MedlinePlus (US National Library of Medicine). B Vitamins. Read 2026-10-23.
- Martens CR, et al. Chronic nicotinamide riboside supplementation is well-tolerated and elevates NAD+ in healthy middle-aged and older adults. Nat Commun 2018;9:1286. PMID 29599478. Read 2026-10-23.
- Orr ME, et al. A randomized placebo-controlled trial of nicotinamide riboside in older adults with mild cognitive impairment. Geroscience 2024;46(1):665-82. PMID 37994989. Read 2026-10-23.
- Brakedal B, et al. The NADPARK study: a randomized phase I trial of nicotinamide riboside supplementation in Parkinson's disease. Cell Metab 2022;34(3):396-407. PMID 35235774. Read 2026-10-23.
- Yoshino M, et al. Nicotinamide mononucleotide increases muscle insulin sensitivity in prediabetic women. Science 2021;372(6547):1224-9. PMID 33888596. Read 2026-10-23.
- European Food Safety Authority. Tolerable Upper Intake Levels for Vitamins and Minerals, February 2006 (Scientific Committee on Food opinions: vitamin B6 expressed 19 October 2000; niacin 17 April 2002). Read 2026-10-23.
- Health Canada. Dietary reference intakes tables: Reference values for vitamins. Page dated 2025-11-19. Read 2026-10-23 through a web-fetch tool.
Education, not medical advice. This page is for general information. It does not diagnose or treat any condition and is not a substitute for care from a qualified health professional. Natural does not automatically mean safe. Ask a clinician or pharmacist before changing your care, especially if you take medication, are pregnant or breastfeeding, or have a health condition.