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Ingredient guide

Is NMN safe? Side effects reported in trials

Written by the Full Measure editorial team, which sells supplements. Approved for publication by the Full Measure owners. Updated .

Drafted with AI assistance from the sources listed below. How we write these

Quick answer

In trials lasting up to 24 weeks, at 250 to 2,000 mg a day, side effects were no more common with NMN than with placebo. Europe's food safety agency judged up to 300 mg a day safe for adults. Use beyond 24 weeks, pregnancy and breastfeeding have not been studied.1,2

Key facts

  • In one 12-week trial, about half of each group reported some complaint: 8 of 15 on NMN and 7 of 15 on placebo, none of them serious.3
  • 1,250 mg a day for 4 weeks caused no changes in blood, urine or body measurements beyond normal variation.4
  • Pooled trials found no rise in the liver enzymes ALT and AST.1
  • A rat study found changes in reproductive organ weights at the highest dose, so Europe's limit carries a safety margin.2

What trials reported

Across 15 randomized trials of 250 to 2,000 mg a day lasting up to 24 weeks, NMN did not increase side effects, serious side effects, dropouts for side effects, or the liver enzymes ALT and AST compared with placebo.1

In a 12-week trial, 8 of 15 people taking 250 mg a day and 7 of 15 taking placebo reported some symptoms; none were serious.3

Single doses of up to 500 mg caused no symptoms in 10 healthy men; bilirubin rose slightly and creatinine, chloride and blood glucose fell slightly, all within normal ranges.5

These trials were small. In the ones Europe's assessors reviewed, 7 to 20 people per group took NMN, so a side effect that affects 1 person in 100 could easily go unseen.2

What the animal study showed

In a 90-day rat study, the highest dose changed the weight of reproductive organs, including a lower ovary weight in females. Europe's assessors set the no-effect level at the dose below it and judged the margin to 300 mg a day in people sufficient.2

The no-effect level in rats was 400 mg per kg of body weight a day, which gave a margin of 93 against 300 mg a day in people.2

The margin shrinks as the daily amount grows. At 500 mg a day it is about 56 for a 70 kg adult, by our arithmetic rather than Europe's, and that amount was not assessed.2

Insulin and blood sugar medicines

In 11 healthy adults taking 250 mg each morning for 12 weeks, insulin measured after lunch rose, by very different amounts from person to person.6

In another small trial, women past menopause with raised blood sugar responded better to insulin in muscle after 10 weeks of 250 mg a day. Neither study enrolled people with diabetes, so if you take insulin or another medicine that lowers blood sugar, ask your doctor before starting NMN.6,7

Blood pressure

In pooled trials, systolic blood pressure did not change and diastolic pressure fell slightly. If you take blood pressure medicine, mention NMN to your doctor.1

Other vitamin B3 products

Europe counts NMN as a source of nicotinamide, so it adds to the vitamin B3 in multivitamins and in niacin, nicotinamide or nicotinamide riboside supplements.2

Europe's food safety agency assessed NMN at up to 300 mg a day and judged that safe for adults who are not pregnant or breastfeeding. Its human data covered up to 900 mg a day for 60 days and 250 mg a day for 24 weeks. Counted as nicotinamide, 300 mg of NMN is about 110 mg, below the 900 mg a day upper level for nicotinamide.2

Who should ask first

Use for longer than 24 weeks has not been studied in trials, so long-term effects are unknown.1,2

  • Anyone pregnant, trying to conceive or breastfeeding: trials required women to avoid pregnancy, and Europe's review excludes pregnancy and breastfeeding2,3,8
  • Anyone under 18
  • Anyone taking prescription medicines or living with a long-term medical condition
  • Anyone already taking niacin, nicotinamide or nicotinamide riboside

No official source we checked names a medicine that interacts with NMN, and no drug interaction study in people was found. That means interactions are unknown, not ruled out, so ask your pharmacist before combining NMN with a prescription.

Questions people ask

Can I take NMN every day, long term?

Trials gave it daily for up to 24 weeks without safety problems. No trial has lasted longer, so the effects of years of use are unknown.1,2

Is NMN safe if I have diabetes?

That has not been settled. Small trials found NMN changed insulin responses, and a 24-week trial in 15 older men with type 2 diabetes, 6 of them on NMN, reported no side effects linked to it. Ask your doctor first, especially if you take medicine that lowers blood sugar.2,6,7

Are side effects different for women and men?

Most of these trials enrolled men and women together, and their reports do not single out a side effect for either sex. Pregnant and breastfeeding women were excluded, so NMN has not been assessed for them.2,3,9

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Sources

  1. Yang W, Huang J, Tang Z, Chen C, Sun Y. Safety and Metabolism-Related Outcomes of Oral Nicotinamide Mononucleotide Supplementation in Adults: A Systematic Review and Meta-Analysis. Nutrients. 2026;18(14):2251. Opened 2026-10-07.
  2. EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA); Turck D, Bohn T, Cámara M, et al. Safety of beta-nicotinamide mononucleotide (β-NMN) pursuant the regulation (EU) 2015/2283 and the bioavailability of nicotinamide from this source in the context of Directive 2002/46/EC. EFSA J. 2026;24(5):e10007. Opened 2026-10-01.
  3. Okabe K, Yaku K, Uchida Y, et al. Oral Administration of Nicotinamide Mononucleotide Is Safe and Efficiently Increases Blood Nicotinamide Adenine Dinucleotide Levels in Healthy Subjects. Front Nutr. 2022;9:868640. Opened 2026-10-07.
  4. Fukamizu Y, Uchida Y, Shigekawa A, Sato T, Kosaka H, Sakurai T. Safety evaluation of β-nicotinamide mononucleotide oral administration in healthy adult men and women. Sci Rep. 2022;12(1):14442. Opened 2026-10-07.
  5. Irie J, Inagaki E, Fujita M, et al. Effect of oral administration of nicotinamide mononucleotide on clinical parameters and nicotinamide metabolite levels in healthy Japanese men. Endocr J. 2020;67(2):153-160. Opened 2026-10-07.
  6. Yamane T, Imai M, Bamba T, Uchiyama S. Nicotinamide mononucleotide (NMN) intake increases plasma NMN and insulin levels in healthy subjects. Clin Nutr ESPEN. 2023;56:83-86. Opened 2026-10-07.
  7. Yoshino M, Yoshino J, Kayser BD, et al. Nicotinamide mononucleotide increases muscle insulin sensitivity in prediabetic women. Science. 2021;372(6547):1224-1229. Opened 2026-10-01.
  8. Yi L, Maier AB, Tao R, 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. Opened 2026-10-01.
  9. Katayoshi T, Uehata S, Nakashima N, Nakajo T, Kitajima N, Kageyama M, Tsuji-Naito K. Nicotinamide adenine dinucleotide metabolism and arterial stiffness after long-term nicotinamide mononucleotide supplementation: a randomized, double-blind, placebo-controlled trial. Sci Rep. 2023;13(1):2786. Opened 2026-10-01.

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.