NMN (nicotinamide mononucleotide) is sold as a daily dietary supplement, so its safety matters as much as its benefits. This guide summarises what human clinical trials show about the side effects of NMN, how long NMN supplementation has been studied, what to avoid, and who should not take it. For the benefits side, see our NMN supplement guide.
What is NMN?
Nicotinamide mononucleotide is a precursor of NAD+ (nicotinamide adenine dinucleotide), a coenzyme that cells need for energy metabolism. NAD+ levels decline with age, and NMN is taken to raise them. Nicotinamide riboside (NR) is another NAD+ precursor sold for the same reason. [1] In randomised trials, oral NMN raised blood NAD+ levels. [2][3]
Is NMN safe? What studies of NMN show
In the trials so far, yes, in the short term. The largest summary is a 2026 meta-analysis of 15 randomised trials of NMN taken by mouth, at 250 to 2,000 mg a day for 14 days to 24 weeks. Compared with placebo or control, oral administration of nicotinamide mononucleotide did not increase [4]:
- overall adverse events (possible side effects of any kind),
- serious adverse events,
- people dropping out because of side effects, or
- side effects in any one body system.
A separate 2026 systematic review of 33 human studies of NAD+ precursors, including NMN supplementation in humans, also found that oral NMN and NR were generally well tolerated over weeks to months. [1]
Side effects of NMN: what each clinical trial found
Because side effects were no more common on NMN than on placebo, the trials do not point to a common side effect of NMN. Individual trials compared NMN or a placebo and looked closely at blood tests and body measurements:
- 1,250 mg a day for 4 weeks: in 31 healthy adults aged 20–65, there were no changes beyond normal variation in blood counts, blood chemistry, urine tests or body composition, and no severe adverse events. [5]
- Up to 900 mg a day for 60 days: in 80 healthy middle-aged adults, no safety issues were found in adverse events, laboratory or clinical measures. [2]
- 1,000 mg once or twice a day for 14 days: in 32 adults aged 55–80, adverse events were no more frequent than on placebo. [3]
- 250 mg of NMN a day for 24 weeks: in 14 older adults (men with diabetes, average age 81), NMN was tolerated without severe adverse events. [6]
Several of these trials had authors from industry. The 2026 meta-analysis, by academic authors, reached the same overall conclusion. [4]
Is NMN toxic to the liver?
The trial evidence on the safety of NMN so far says no. In the 2026 meta-analysis, NMN did not significantly raise the liver enzymes ALT or AST, which are standard markers of liver stress. [4] The 4-week trial at 1,250 mg a day also found no blood chemistry changes beyond normal variation. [5]
Does NMN affect blood sugar or blood pressure?
NMN did not change fasting glucose, insulin, HbA1c or lipids in a 2024 meta-analysis of 8 trials. [7] It lowered resting diastolic blood pressure by about 2 mmHg in a 2026 meta-analysis. [8] That is a small change, but people taking blood-pressure medicine should tell their doctor before adding NMN.
What happens if you take NMN every day?
Every trial above gave NMN once or twice daily, so daily use is what has been tested. Blood NAD+ rises within weeks of daily NMN supplementation. [2][3] The limit is time: the longest trials ran about 24 weeks. [4] Nobody knows yet whether taking NMN for years is safe.
NMN and cancer: what is known
No human trial has been long enough or large enough to show whether NMN raises or lowers cancer risk. The 2026 meta-analysis authors call for larger and longer trials to confirm long-term safety. [4] Claims in either direction go beyond the evidence. Anyone with a current or past cancer should speak to their oncologist before taking NMN.
Can NMN interact with medicines?
The trials cited here were not designed to study interactions with medicines. Because the effect of NMN on diastolic blood pressure is small but measurable [8], people on blood-pressure medicine, and anyone on long-term prescription treatment, should check with their doctor before taking NMN.
What to avoid when taking NMN
- Doses above those tested. Trials have used 250 to 2,000 mg of NMN a day. [4] There is no safety data for a higher dose of NMN.
- Products without a certificate of analysis. You cannot check purity or contamination without one.
- Replacing medical treatment. NMN has not been shown to treat diabetes, muscle loss or any disease. [7][9]
Who should not take NMN?
- Pregnant or breastfeeding women. None of the trials cited here studied them, so there is no safety data.
- Children and teenagers. Not studied.
- People with a medical condition or on prescription medicine, unless their doctor agrees.
Weighing the potential benefits of NMN against the risks
Safety only matters in relation to benefit. The effect of NMN on NAD+ is clear, but the benefits of NMN in people are modest so far:
- No effect on fasting glucose, insulin, HbA1c or lipids in a meta-analysis of 8 trials. [7]
- No effect on muscle mass, grip strength or gait speed in older adults. [9]
- A small fall in diastolic blood pressure, about 2 mmHg; NMN may help blood pressure slightly, but the authors call this preliminary. [8]
- Clinical effectiveness for anti-ageing and wellness outcomes is inconclusive. [1]
So NMN looks low-risk in the short term, with few adverse effects and limited proven benefit. Potential side effects of long-term use remain unknown. More detail is in our guide to the potential benefits of NMN.
How much NMN is safe?
Trials have used 250 to 2,000 mg a day. [4] One safety trial tested 1,250 mg once daily for 4 weeks [5], and another gave 1,000 mg twice daily for 14 days. [3] These are research doses, not a recommended intake.
Product quality is part of safety
Product quality also matters for safety: wrong content, contamination and poor storage are risks with any supplement. Check that the NMN certificate of analysis shows HPLC purity with the batch result, heavy metals, and microbiology including Salmonella. Our NMN supplier page lists the tests on FC Materials’ NMN COA. For a question this guide does not cover, WhatsApp us.
What the research says
- A meta-analysis of 15 trials (up to 24 weeks) found no increase in adverse events, serious adverse events or liver enzymes with NMN. [4]
- 1,250 mg a day for 4 weeks caused no changes beyond normal variation in 31 healthy adults. [5]
- Long-term safety beyond about six months has not been studied. [4]
These summaries describe published research on the ingredient. They are not claims for any finished product; claims on finished products must meet the rules of the market where they are sold.
References
- Gallagher C, Emmanuel OO. NAD+ supplementation for anti-aging and wellness: a PRISMA-guided systematic review of preclinical and clinical evidence. Ageing Res Rev. 2026;116:103057. doi:10.1016/j.arr.2026.103057
- Yi L, et al. The efficacy and safety of β-nicotinamide mononucleotide (NMN) supplementation in healthy middle-aged adults: a randomized, multicenter, double-blind, placebo-controlled, parallel-group, dose-dependent clinical trial. GeroScience. 2023;45(1):29-43. doi:10.1007/s11357-022-00705-1
- Pencina KM, et al. MIB-626, an oral formulation of a microcrystalline unique polymorph of β-nicotinamide mononucleotide, increases circulating nicotinamide adenine dinucleotide and its metabolome in middle-aged and older adults. J Gerontol A Biol Sci Med Sci. 2023;78(1):90-96. doi:10.1093/gerona/glac049
- 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. doi:10.3390/nu18142251
- Fukamizu Y, et al. Safety evaluation of β-nicotinamide mononucleotide oral administration in healthy adult men and women. Sci Rep. 2022;12(1):14442. doi:10.1038/s41598-022-18272-y
- Akasaka H, et al. Effects of nicotinamide mononucleotide on older patients with diabetes and impaired physical performance: a prospective, placebo-controlled, double-blind study. Geriatr Gerontol Int. 2023;23(1):38-43. doi:10.1111/ggi.14513
- Chen F, et al. Effects of nicotinamide mononucleotide on glucose and lipid metabolism in adults: a systematic review and meta-analysis of randomised controlled trials. Curr Diab Rep. 2024;25(1):4. doi:10.1007/s11892-024-01557-z
- Zhang M, et al. Effects of nicotinamide mononucleotide supplementation on blood pressure: a systematic review and meta-analysis of randomized controlled trials. Nutrients. 2026;18(6):890. doi:10.3390/nu18060890
- 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;16(3):e13799. doi:10.1002/jcsm.13799
Need NMN with a full COA?
FC Materials supplies NMN powder with a certificate of analysis per batch, covering HPLC purity, heavy metals and microbiology. WhatsApp us for the current COA.
