NR side effects: what trials show about nicotinamide riboside

Updated November 3, 2026. For information only, not medical advice. This guide has no affiliate links. It links to one best-of page that may carry them (see our affiliate disclosure). Availability varies by country; check local rules before buying.

In a nutshell

• Quick answer: in the small human trials we found, nicotinamide riboside (NR) was generally well tolerated. Reported side effects were mild and uncommon (nausea, flushing, leg cramps, bruising) and not clearly different from placebo.
• How long: most trials ran 6 to 10 weeks. The longest, 52 weeks, was in people with early Parkinson’s disease, so it says less about healthy adults.
• Funding: the earlier trials had supplier support, and some authors of the 52-week trial hold NR patents licensed to a supplier.
• Evidence rating: short-term tolerability in humans is Early. Long-term safety in healthy people is Very early: we found no such trial.

New to NR? Start with our NR beginner’s guide. For its cousin, see NMN side effects and NMN vs NR.

What did the trials report about NR side effects?

Basis: PMIDs 31278280, 29599478, 37994989, 42848371 (all human trials).

• 8 weeks, healthy overweight adults (Conze 2019). No reports of flushing, and no significant differences in adverse events between NR and placebo or between doses. Funded by ChromaDex, the NR supplier, which employs two authors.
• 6 weeks, healthy adults aged 55 to 79, with a placebo phase (Martens 2018). Of 30 people enrolled, 7 reported 14 mild side effects in total. On NR: nausea, flushing, leg cramps and increased bruising, one report each. No serious events, and both drop-outs for side effects were on placebo. ChromaDex supplied the pills and part of the funding.
• 10 weeks, 20 older adults with mild cognitive impairment (Orr 2024). Adverse event reporting did not differ from placebo. ChromaDex supplied the NR.
• 52 weeks, 410 people with early Parkinson’s (NOPARK, JAMA 2026). Serious adverse events: 17 of 205 on NR (8.3%) and 29 of 205 on placebo (14.1%). But disease and non-motor symptom scores were worse on NR, and the authors said the results do not support NR as a treatment for the disease.

Doses used in trials

Basis: PMIDs 31278280, 29599478, 37994989, 42848371.

Trials used 100, 300 or 1,000 mg a day for 8 weeks (Conze), 500 mg twice a day for 6 weeks (Martens), up to 1 g a day for 10 weeks (Orr) and 500 mg twice a day for 52 weeks (NOPARK). The Martens authors said their dose exceeded the label-recommended dose of the product they used and “should be considered investigational.” These are doses studied, not advice. We found no official upper limit for NR in the sources we opened.

NR vs niacin and niacinamide

Basis: NIH Office of Dietary Supplements (ODS) niacin fact sheet, updated November 18, 2022; PMIDs 31278280, 29599478.

NIH uses “niacin” as an umbrella for nicotinic acid, nicotinamide (niacinamide) and related forms such as NR, but notes NR supplements are not marketed or labeled as sources of niacin. NIH says 30 to 50 mg or more of nicotinic acid typically causes skin flushing, while nicotinamide does not. In NR trials flushing was rare: none in Conze, and in Martens one event on NR and two on placebo. That is an observation about these trials, not proof NR never causes flushing.

What we do not know

Basis: PMIDs 37478182, 29599478, 42848371.

• Long-term safety in healthy adults. The healthy-adult trials we read lasted 6 to 8 weeks.
• Who it suits. Two of the four trials had 30 or fewer people. In the sources we opened we found no data on pregnancy, breastfeeding or medicine interactions.
• How much it helps. A 2023 review of 25 human NR studies found “few clinically relevant effects” and a tendency to exaggerate them (Damgaard and Treebak).

Who should ask a clinician first: anyone who takes medicines, has a health condition, or is pregnant or breastfeeding. People with Parkinson’s disease should talk to their care team, given the NOPARK result.

FAQ

What are the side effects of NR?

In the small trials we read, side effects were mild and uncommon. A 6-week trial listed nausea, flushing, leg cramps and increased bruising on NR, one report each. An 8-week trial saw no flushing and no significant difference from placebo. No serious problems stood out in healthy adults, but the trials were short and small.

Basis: US Google autocomplete, November 3, 2026 (“nr side effects”); PMIDs 29599478, 31278280.

Is nicotinamide riboside safe?

It was generally well tolerated in short human trials, mostly 6 to 10 weeks, and several had ties to the NR maker. Long-term safety in healthy people has not been shown. In a 52-week Parkinson’s trial, symptom scores were worse on NR. Ask a doctor or pharmacist first if you take medicines.

Basis: US Google autocomplete, November 3, 2026 (“nr supplement side effects”); PMIDs 31278280, 29599478, 42848371.

What is the nicotinamide riboside dosage per day in studies?

Trials gave 100, 300 or 1,000 mg a day for 8 weeks, 1,000 mg a day (500 mg twice daily) for 6 weeks, up to 1 g a day for 10 weeks, and 1,000 mg a day for 52 weeks in Parkinson’s disease. These are study doses, not recommendations, and we found no official upper limit.

Basis: US Google autocomplete, November 3, 2026 (“nicotinamide riboside dosage per day”); PMIDs 31278280, 29599478, 37994989, 42848371.

What this means for you

What this means for you

• Side effects so far: mild and uncommon in short human trials.
• What is missing: long-term trials in healthy adults. Evidence rating: short-term tolerability Early; long-term safety Very early.
• Who to ask: a doctor or pharmacist, if you take medicines, have a health condition, or are pregnant or breastfeeding.
• If you look at products: our best NR supplement page compares them and may contain affiliate links (see our affiliate disclosure).

Sources

Pages were opened on November 3, 2026.

1. Conze D, Brenner C, Kruger CL. Safety and metabolism of long-term administration of NIAGEN (nicotinamide riboside chloride) in a randomized, double-blind, placebo-controlled clinical trial of healthy overweight adults. Sci Rep 2019. PubMed
2. Martens CR et al. Chronic nicotinamide riboside supplementation is well-tolerated and elevates NAD+ in healthy middle-aged and older adults. Nat Commun 2018. PubMed · PMC full text
3. Orr ME et al. A randomized placebo-controlled trial of nicotinamide riboside in older adults with mild cognitive impairment. GeroScience 2024. PubMed
4. Brakedal B et al. Nicotinamide riboside for patients with early-stage Parkinson disease: the NOPARK randomized clinical trial. JAMA, 2026. PubMed
5. Damgaard MV, Treebak JT. What is really known about the effects of nicotinamide riboside supplementation in humans. Sci Adv 2023. PubMed
6. NIH Office of Dietary Supplements (US). Niacin: Fact Sheet for Health Professionals (updated November 18, 2022). Used only for niacin forms and flushing, not for any product’s legal status.

This article is for information only and is not medical advice. Speak to a healthcare professional before changing medication or supplements.