NMN and NR for Renal Protection: What the Evidence Actually Shows

What the animal and cell studies show

In human kidney cells (HK-2 proximal tubular cells), NMN reduced the DNA damage and cell senescence caused by hydrogen peroxide and hypoxia [1]. In mice with unilateral ischemia-reperfusion injury, NMN reduced tubular DNA damage, senescence and inflammation, and reduced fibrosis whether it was given before the injury or during recovery [1].

The clearest functional animal result used a different precursor. In mice, loss of PGC1alpha after renal ischemia produced a local nicotinamide deficit, fat accumulation and failure to regain normal kidney function; giving nicotinamide raised local NAD+, reduced fat accumulation and improved renal function, and nicotinamide reversed established ischemic AKI and also prevented AKI in an unrelated toxic model [2]. In a separate mouse AKI model, renal NAD+ fell, quinolinate rose and the enzyme QPRT declined [12].

Is there any human kidney data?

The closest human signal involves nicotinamide, not NMN or NR. In critically ill patients, an elevated urinary quinolinate to tryptophan ratio, an indicator of reduced QPRT, predicted AKI and other adverse outcomes. In the same paper, a phase 1 placebo-controlled study of oral nicotinamide showed dose-related increases in circulating NAD+ metabolites, was well tolerated, and was associated with less AKI [12]. A phase 1 study of a different precursor does not establish that NMN or NR protects human kidneys.

What the human NMN trials actually measured

Yoshino 2021 (Science). A 10-week randomized, placebo-controlled, double-blind trial of NMN 250 mg per day in postmenopausal women with prediabetes who were overweight or obese. Insulin-stimulated glucose disposal, measured by hyperinsulinemic-euglycemic clamp, rose with NMN and did not change with placebo. The outcomes reported were muscle insulin sensitivity, insulin signaling and muscle remodeling genes, not kidney measures. The trial was single-center and small, and a published comment and response disputed the analysis [13].

Yi 2023 (GeroScience). Eighty healthy middle-aged adults took placebo or NMN 300, 600 or 900 mg daily for 60 days. Blood NAD rose in every NMN group (p <= 0.001), highest at 600 and 900 mg, and six-minute walk distance was greater than placebo in all NMN groups. There were no safety issues on adverse-event, laboratory and clinical monitoring [6].

Okabe 2022 (Front Nutr). NMN 250 mg per day or placebo for 12 weeks in 30 healthy adults produced no abnormalities in physiological or laboratory tests and no obvious adverse effects; whole-blood NAD+ rose [5].

Fukamizu 2022 (Sci Rep). NMN 1,250 mg once daily for up to 4 weeks in 31 healthy adults aged 20 to 65 produced no severe adverse events and no changes beyond physiological variation in hematology, biochemistry, urine or body composition analyses [9].

What the human NR trials actually measured

In a 2 by 6-week randomized, double-blind, placebo-controlled crossover trial of middle-aged and older adults, NR 500 mg twice daily was well tolerated and stimulated NAD+ metabolism; the authors suggested future trials assess NR for reducing blood pressure and arterial stiffness [7].

In a trial of 40 sedentary obese men assigned to NR 1,000 mg twice daily or placebo for 12 weeks, NR did not improve insulin sensitivity, energy expenditure, lipolysis or body composition, with no serious adverse events [10]. In NR-SAFE 2023, 20 people with Parkinson's disease were assigned equally to NR 1,500 mg twice daily or placebo for 4 weeks, with no moderate or severe adverse events [11].

Blood NAD+ is not the same as kidney NAD+

Oral NMN and NR raise NAD+ or NAD+ metabolites in human blood [5][6][7]. Whether that reaches an organ is a separate question. In 12 men aged 70 to 80, NR 1 g per day for 21 days did not raise muscle NAD+ (210 versus 197 pmol/mg, p=0.22), although a marker of NAD+ synthesis doubled, and mitochondrial respiration, grip strength, insulin sensitivity and muscle blood flow were unchanged [8].

The clinical picture from pooled trials is similarly modest. A 2025 meta-analysis found NMN had no significant effect on skeletal muscle index, handgrip strength, gait speed or the 5-times chair stand in older adults [14]. Another 2025 meta-analysis of 12 studies and 513 participants found NMN raised blood NAD, but most clinically relevant outcomes, including fasting glucose, triglycerides and cholesterol, were not significantly different from control; risk of bias had some concerns in 7 studies and was high in 5 [15].

Safety questions that matter more in kidney disease

Kidney disease itself. Pregnancy, breastfeeding, children and people with cancer or kidney or liver disease were not studied in the cited trials, so safety in those groups is unknown [3].

Duration. Human safety data beyond about 12 weeks are lacking; the trials were short and small [3].

Drug interactions. No human drug-interaction studies of NMN or NR (CYP, transporter or pharmacodynamic) were found in a PubMed search [3], so nothing is known about combining either supplement with specific prescription drugs.

Cancer. Chronic NAD+ boosting has been raised as a theoretical cancer concern, but no human data were identified [3].

Regulatory status. NMN and NR are sold in the US as oral dietary supplements; neither is an FDA-approved drug, and no NAD+ precursor product is FDA-approved to treat aging or any disease [4]. For NR, FDA's 2016 response to GRAS notice GRN 000635 stated it had no questions about the company's own GRAS conclusion and had not made its own GRAS determination [16].

Doses used in human studies

There is no official RDA, upper limit or FDA-endorsed dose for NMN or NR; the numbers below are doses that trials used, not recommendations. NMN: 250 mg per day for 6 to 12 weeks [13][5][17]; 300 to 900 mg per day for 60 days [6]; 1,250 mg once daily for up to 4 weeks [9]. NR: 1,000 mg per day for 21 days [8] or six weeks [7]; 2,000 mg per day for 12 weeks [10]; 3,000 mg per day for 4 weeks [11].