Beginner’s guide

NMN Side Effects: What Human Trials and Reviews Show

Updated Nov 3, 2026 · By LongevityBeginners Editorial Team

Updated November 3, 2026. For information only, not medical advice. This guide does not say NMN is safe for you. It reports what trials measured and for how long. It links to our medical disclaimer. We do not link to NMN products. Availability varies by country; check local rules before buying. Related: is NMN FDA approved?

Quick answer: short trials found no rise in side effects; long-term data are missing

Basis: US Google autocomplete, Nov 3, 2026 (“nmn side effects”, “is nmn safe to take daily”); PMID 42514320.

A 2026 meta-analysis of NMN trials found no increase in overall, serious or withdrawal-related adverse events. The trials ran from 14 days to 24 weeks. We found no trial that followed people for years, so long-term effects are not known. If you notice a symptom, do not guess the cause; speak to a clinician.

What the 2026 meta-analysis found

Basis: PMID 42514320 (Yang et al., Nutrients, July 10, 2026).

The meta-analysis pooled 15 trials of oral NMN in adults, with 10 trials in the safety analyses. Doses were 250 to 2,000 mg a day for 14 days to 24 weeks. Compared with placebo, NMN did not increase overall, serious, withdrawal-related or system-specific adverse events. Liver enzymes (ALT and AST) did not rise significantly.

It also found no significant effects on body weight, BMI, fasting glucose, HbA1c, blood fats or systolic blood pressure. Diastolic blood pressure fell slightly, and a measure of insulin resistance (HOMA-IR) showed a non-significant downward trend. The authors said larger and longer trials are needed, and reported no conflict of interest. A 2026 review of NAD+ boosters also described oral NMN and NR as generally well tolerated over weeks to months. Our dosage guide lists the amounts used.

What individual trials reported

Basis: PMIDs 36482258, 35479740, 35927255, 33888596, 36797393, 38789831.

900 mg for 60 days. In a 2023 trial, 80 healthy middle-aged adults received placebo, 300, 600 or 900 mg a day. The authors reported no safety issues and good tolerance up to 900 mg a day. Some authors were employees of two companies (Abinopharm and ABA Chemicals).
250 mg for 12 weeks. In a 2022 trial, 30 healthy people (15 on NMN) had no abnormalities in physiological or lab tests and no obvious adverse effects. Mitsubishi employees prepared the NMN and placebo.
250 mg in older men. Igarashi 2022 found NMN well tolerated for 6 or 12 weeks. Mitsubishi Corporation Life Sciences funded it and employed three authors.
250 mg in women with prediabetes. In Yoshino 2021, 25 postmenopausal women took part for 10 weeks. The full text reports no adverse events and no abnormal standard blood tests. Its authors report patent and licensing ties.
125 mg twice a day for 12 weeks. Katayoshi 2023 studied 36 healthy middle-aged adults, found NMN well tolerated and reported no adverse events. The authors are from DHC Corporation.
250 mg for 12 weeks in older adults. Morifuji 2024 found no adverse effects related to the product. Meiji funded it, and three of its four authors work for Meiji.

These trials were small (30 to 108 people) and short (up to 12 weeks).

EFSA’s opinion in one paragraph

Basis: PMID 42125559 (EFSA NDA Panel, EFSA Journal, May 2026).

The European Food Safety Authority published a safety opinion in 2026. It assessed an intended use of up to 300 mg a day as a niacin source for adults, excluding pregnant and lactating women. A 90-day rat study showed effects on reproductive organs. EFSA judged the margin between that finding and the intended use (93) sufficient, and concluded NMN is safe under the proposed conditions. This is a scientific opinion about a proposed use, not advice to use NMN.

Side effects people ask about

Basis: US Google autocomplete, Nov 3, 2026 (“nmn side effects liver”, “nmn side effects kidney”, “nmn side effects hair loss”, “nmn side effects anxiety”, “nmn side effects weight gain”); PMIDs 42514320, 35927255.

Liver: the meta-analysis found no significant rise in ALT or AST. Igarashi 2022 also found no significant difference in liver enzymes between NMN and placebo in older men over 12 weeks.
Kidney: the one source we found is Igarashi 2022. Its blood tests of kidney function did not differ between NMN and placebo after 12 weeks at 250 mg a day. That was a safety lab check in a small group, not a kidney study. We found no trial of NMN in people with kidney disease.
Weight gain: the meta-analysis found no significant effect on body weight or BMI. Igarashi 2022 found no effect on body composition.
Hair loss and anxiety: we found no trial data on these. That does not show they never happen. It means the studies we read did not report them.

NMN side effects in women and in men

Basis: US Google autocomplete, Nov 3, 2026 (“nmn side effects women”, “nmn side effects men”); PMIDs 33888596, 35927255.

We found no trial that compared side effects between women and men. The women’s trial (Yoshino 2021, postmenopausal women with prediabetes, 10 weeks) and the men’s trial (Igarashi 2022, older men, 6 or 12 weeks) both reported good tolerance at 250 mg a day. Each was small, so rare effects could be missed.

What we do not know

Basis: PMIDs 42514320, 42125559; NIH Office of Dietary Supplements.

Long-term use: the longest trials in the meta-analysis ran 24 weeks.
Pregnancy and breastfeeding: EFSA’s assessed use excluded pregnant and lactating women. We found no trial data for them. The NIH Office of Dietary Supplements advises caution with supplements in pregnancy or nursing.
Medicines: the NIH Office of Dietary Supplements says supplements can interact with some medicines. We found no NMN interaction trials.
People with health conditions: most trials enrolled healthy adults, apart from the women with prediabetes.

Who should ask a clinician first

Basis: NIH Office of Dietary Supplements, “Dietary Supplements: What You Need to Know” (updated January 4, 2023).

Ask a clinician or pharmacist before using NMN if you are pregnant or breastfeeding, take prescription medicines, have a medical condition, or have surgery planned. The NIH says to tell your health care providers about every supplement you use, and to report a bad reaction to them. Read our guide to choosing an NMN supplement before you buy anything.

If you are comparing NAD+ precursors, our NMN vs NR guide, NMN guide and best NR supplement page may help. The last may contain affiliate links; NMN has none on this site.

FAQ

What are the side effects of NMN?

In the trials we read, side effects did not increase compared with placebo. A 2026 meta-analysis of 15 trials found no increase in overall, serious or withdrawal-related adverse events compared with placebo. The trials were short, from 14 days to 24 weeks. Long-term effects are not known, and rare effects could be missed in small trials.

Basis: US Google autocomplete, Nov 3, 2026 (“nmn side effects”); PMID 42514320.

Is NMN safe to take every day?

We cannot say it is safe, and this is not advice. Trials gave NMN daily for 14 days to 24 weeks and found no increase in adverse events. EFSA assessed up to 300 mg a day in adults, excluding pregnant and lactating women. No trial we found ran for years, so long-term daily use is unstudied.

Basis: US Google autocomplete, Nov 3, 2026 (“is nmn safe to take daily”); PMIDs 42514320, 36482258, 42125559.

Does NMN affect the liver or kidneys?

In the meta-analysis, liver enzymes (ALT and AST) did not rise significantly. In one 12-week trial of older men taking 250 mg a day, blood markers of kidney function did not differ from placebo. Both are short, small-scale safety checks. We found no trials in people with liver or kidney disease.

Basis: US Google autocomplete, Nov 3, 2026 (“nmn side effects liver”, “nmn side effects kidney”); PMIDs 42514320, 35927255.

Does NMN cause hair loss or weight gain?

We found no trial data on hair loss. For weight, the 2026 meta-analysis found no significant effect on body weight or BMI, and one trial in older men found no effect on body composition. Absence of reports in short trials does not rule out an effect in individuals. Speak to a clinician about any change.

Basis: US Google autocomplete, Nov 3, 2026 (“nmn side effects hair loss”, “nmn side effects weight gain”); PMIDs 42514320, 35927255.

NMN side effects in women vs men?

We found no trial that compared them. A trial in 25 postmenopausal women with prediabetes (10 weeks) reported no adverse events. A trial in older men (6 or 12 weeks) reported good tolerance. Both used 250 mg a day and were small, so differences between the sexes cannot be ruled in or out.