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NMN and NR After Bariatric Surgery: What the Evidence Actually Shows

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At a glance

  • Evidence after surgery / The trials cited were in other groups, not post-bariatric patients
  • Regulatory status / Dietary supplements in the US; neither is an FDA-approved drug [8]
  • Doses studied / NMN 250 to 1,250 mg/day [1][9]; NR 1 to 3 g/day [10][11]
  • Blood NAD+ / Rises with oral NMN or NR in randomized trials [1][2][3]
  • Muscle NAD+ / Not significantly raised by NR 1 g/day for 21 days in 12 older men [10]
  • Drug interactions / No human interaction studies found [12]

What the human trials show

The trials that exist were run in other groups: postmenopausal women with prediabetes, men with obesity, and people with Parkinson's disease [4][5][11]. Their results are mixed.

In postmenopausal women with prediabetes who were overweight or obese, a 10-week randomized, placebo-controlled trial of NMN increased insulin-stimulated glucose disposal and muscle insulin signaling; the same measures did not change with placebo [4].

Other trials were null. NR 1,000 mg twice daily for 12 weeks did not improve insulin sensitivity or glucose metabolism in 40 sedentary men with obesity [5]. In 12 men aged 70-80, NR 1 g/day for 21 days did not significantly raise muscle NAD+ and did not change mitochondrial bioenergetics in muscle [10].

Two 2025 meta-analyses found NMN had no significant effect on skeletal muscle index, handgrip strength, gait speed or the 5-times chair stand [6], and most metabolic outcomes were not significantly different from control across 12 trials with 513 participants [7].

Doses and side effects in trials

These are doses studied in trials, not recommended doses. NMN has been tested at 250 mg/day for 6 to 12 weeks [1][13], 300 to 900 mg/day for 60 days [2], and 1,250 mg once daily for up to 4 weeks [9]. NR has been tested at 1 g/day for 21 days [10], at 500 mg twice daily (1 g/day) in a six-week crossover [3], and at 1,500 mg twice daily for 4 weeks [11].

NMN 1,250 mg once daily for up to 4 weeks in 31 healthy adults caused no severe adverse events and no changes beyond normal physiological variation in blood, urine or body composition tests [9]. NMN 250 mg/day for 12 weeks in 30 healthy adults caused no abnormalities in laboratory tests and no obvious adverse effects [1]. NR 1,500 mg twice daily for 4 weeks in 20 people with Parkinson's disease caused no moderate or severe adverse events, and NR was well tolerated in a six-week crossover trial in healthy middle-aged and older adults [11][3]. Human trials have been short and small, and safety beyond about 12 weeks is not established [12]. No human drug-interaction studies of NMN or NR with any prescription drug were found [12].

Regulatory status

Both are sold in the US as oral dietary supplements, and neither is an FDA-approved drug [8]. Reports of FDA's response letter dated 2025-09-29 say FDA concluded NMN is not excluded from the dietary supplement definition, so it may be lawfully marketed subject to new-dietary-ingredient notification rules [8]. For NR, FDA answered a company's GRAS notice with a 'no questions at this time' letter in 2016 and stated it had not made its own GRAS determination [14].

Frequently asked questions

Is NMN safe to take after bariatric surgery?
Safety after bariatric surgery is unknown, because the trials cited did not enroll those patients. In adults who had not had surgery, NMN 1,250 mg once daily for up to 4 weeks caused no severe adverse events, and most trials ran 12 weeks or less [9][12]. People with kidney or liver disease, cancer, pregnancy or breastfeeding were not studied in the cited trials, so safety in those groups is unknown [12].
Which absorbs better after gastric bypass, NMN or NR?
The trials cited do not address absorption of either supplement after gastric bypass or sleeve gastrectomy. In adults with an intact gut, oral NMN and NR both raise blood NAD+ [1][2][3].
Do NMN or NR interact with metformin or GLP-1 drugs?
No human interaction studies of NMN or NR with any prescription drug were found [12]. Whether combining either supplement with metformin or a GLP-1 receptor agonist changes the effect of either drug is unknown.

References

  1. Okabe K, Yaku K, Uchida Y, Fukamizu Y, Sato T, Sakurai T, 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. Oral Administration of Nicotinamide Mononucleotide Is Safe and Efficiently Increases Blood Nicotinamide Adenine Dinucleotide Levels in Healthy Subjects
  2. Yi L, Maier AB, Tao R, Lin Z, Vaidya A, Pendse S, 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. 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
  3. Martens CR, Denman BA, Mazzo MR, Armstrong ML, Reisdorph N, McQueen MB, et al. Chronic nicotinamide riboside supplementation is well-tolerated and elevates NAD+ in healthy middle-aged and older adults. Nat Commun. 2018;9(1):1286. Chronic nicotinamide riboside supplementation is well-tolerated and elevates NAD+ in healthy middle-aged and older adults
  4. Yoshino M, Yoshino J, Kayser BD, Patti GJ, Franczyk MP, Mills KF, et al. Nicotinamide mononucleotide increases muscle insulin sensitivity in prediabetic women. Science. 2021;372(6547):1224-1229. Nicotinamide mononucleotide increases muscle insulin sensitivity in prediabetic women
  5. Dollerup OL, Christensen B, Svart M, Schmidt MS, Sulek K, Ringgaard S, et al. A randomized placebo-controlled clinical trial of nicotinamide riboside in obese men: safety, insulin-sensitivity, and lipid-mobilizing effects. Am J Clin Nutr. 2018;108(2):343-353. A randomized placebo-controlled clinical trial of nicotinamide riboside in obese men: safety, insulin-sensitivity, and lipid-mobilizing effects
  6. Prokopidis K, Moriarty F, Bahat G, McLean J, Church DD, Patel HP. 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. The Effect of Nicotinamide Mononucleotide and Riboside on Skeletal Muscle Mass and Function: A Systematic Review and Meta-Analysis
  7. Zhang J, Poon ET, Wong SH. Efficacy of oral nicotinamide mononucleotide supplementation on glucose and lipid metabolism for adults: a systematic review with meta-analysis on randomized controlled trials. Crit Rev Food Sci Nutr. 2025;65(22):4382-4400. Efficacy of oral nicotinamide mononucleotide supplementation on glucose and lipid metabolism for adults: a systematic review with meta-analysis on randomized controlled trials
  8. FDA response to citizen petition, docket FDA-2023-P-0872 (regulations.gov record). FDA response to citizen petition, docket FDA-2023-P-0872
  9. 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. Safety evaluation of β-nicotinamide mononucleotide oral administration in healthy adult men and women
  10. Elhassan YS, Kluckova K, Fletcher RS, Schmidt MS, Garten A, Doig CL, et al. Nicotinamide Riboside Augments the Aged Human Skeletal Muscle NAD+ Metabolome and Induces Transcriptomic and Anti-inflammatory Signatures. Cell Rep. 2019;28(7):1717-1728.e6. Nicotinamide Riboside Augments the Aged Human Skeletal Muscle NAD+ Metabolome and Induces Transcriptomic and Anti-inflammatory Signatures
  11. Berven H, Kverneng S, Sheard E, Søgnen M, Af Geijerstam SA, Haugarvoll K, et al. NR-SAFE: a randomized, double-blind safety trial of high dose nicotinamide riboside in Parkinson's disease. Nat Commun. 2023;14(1):7793. NR-SAFE: a randomized, double-blind safety trial of high dose nicotinamide riboside in Parkinson's disease
  12. Freeberg KA, Udovich CC, Martens CR, Seals DR, Craighead DH. Dietary Supplementation With NAD+-Boosting Compounds in Humans: Current Knowledge and Future Directions. J Gerontol A Biol Sci Med Sci. 2023;78(12):2435-2448. Dietary Supplementation With NAD+-Boosting Compounds in Humans: Current Knowledge and Future Directions
  13. Igarashi M, Nakagawa-Nagahama Y, Miura M, Kashiwabara K, Yaku K, Sawada M, et al. Chronic nicotinamide mononucleotide supplementation elevates blood nicotinamide adenine dinucleotide levels and alters muscle function in healthy older men. NPJ Aging. 2022;8(1):5. Chronic nicotinamide mononucleotide supplementation elevates blood nicotinamide adenine dinucleotide levels and alters muscle function in healthy older men
  14. Agency Response Letter GRAS Notice No. GRN 000635 | FDA. Agency Response Letter GRAS Notice No. GRN 000635 | FDA
Evidence overview for NMN and NR After Bariatric Surgery: What the Evidence Actually Shows