Nicotinamide (Vitamin B3)

What it is

Nicotinamide, also called niacinamide, is a form of vitamin B3 [1]. The body makes it partly from the amino acid tryptophan, and it is also found in fish, meat, grains and dairy products [2]. It is taken by mouth as a supplement and applied to the skin in creams and moisturizers [3][1].

How it might work

Proposed mechanisms: nicotinamide helps repair DNA damage caused by ultraviolet (UV) light and reduces the immune suppression that UV causes in the skin [4]. In healthy volunteers, oral and topical nicotinamide reduced the immune suppression caused by photodynamic therapy by 66% and 59% [5]. Whether these effects prevent cancers is tested in the trials below.

What the research says

Skin cancer prevention in people with earlier skin cancers. The main trial, ONTRAC, randomly assigned 386 people who had had at least two non-melanoma skin cancers in the previous 5 years to 500 mg of nicotinamide twice daily or placebo for 12 months: new non-melanoma skin cancers were 23% lower with nicotinamide (95% CI 4 to 38), squamous-cell carcinomas 30% lower (0 to 51) and basal-cell carcinomas 20% lower (-6 to 39, not significant), and there was no evidence of benefit after nicotinamide was stopped [3]. A 2022 meta-analysis of randomized trials (5 trials, 552 patients) found a rate ratio of 0.50 for skin cancers (95% CI 0.29 to 0.85; moderate-strength evidence), with heterogeneity that the authors explained by risk of bias [6]. A 2023 meta-analysis that pooled immunocompetent and immunosuppressed patients (4 trials) found no significant reduction in non-melanoma skin cancer (RR 0.82, 0.61 to 1.12) and judged the evidence insufficient [2]. A 2026 systematic review of randomized trials in adults with normal immune systems reported 30% fewer squamous-cell cancers across two trials and said nicotinamide shows promise [7]. A US veterans' cohort study (12,287 users matched with 21,479 non-users) linked nicotinamide to 14% lower skin cancer risk, and to 54% lower risk when started after a first skin cancer, but it was observational [8].

Precancerous patches (actinic keratoses). In ONTRAC, actinic keratoses were 13% fewer with nicotinamide at 12 months (14% fewer at 6 months and 20% fewer at 9 months) [3]. The 2026 review reported 13% to 35% fewer actinic keratoses across two trials [7].

Organ-transplant recipients. In the ONTRANS phase 3 trial of 158 transplant recipients with at least two earlier keratinocyte cancers, 500 mg twice daily for 12 months made no difference: 207 new cancers with nicotinamide versus 210 with placebo (rate ratio 1.0, 0.8 to 1.3), though the trial stopped early because of poor recruitment [4]. A pilot in 21 kidney-transplant recipients also found no reduction in actinic keratoses [9]. A 2019 systematic review rated the effect of nicotinamide on skin cancer in transplant recipients uncertain (2 trials, 60 participants) [10]. The veterans' study found no overall significant risk reduction in transplant recipients [8].

Creams for sun-damaged skin. In a 12-week split-face trial of 50 white women, 5% niacinamide cream reduced fine lines and wrinkles, dark spots, red blotchiness and yellowing, and improved elasticity versus the vehicle on the other half of the face [1]. A moisturizer with 2% niacinamide plus 2% tranexamic acid reduced irregular pigmentation versus vehicle in 42 Korean women over 8 weeks, but it was a combination product [11]. A 2% niacinamide moisturizer lowered sebum excretion in 100 Japanese volunteers after 2 and 4 weeks; in 30 Caucasian volunteers it lowered casual sebum levels but not the sebum excretion rate [12].

Kidney failure and phosphate. A systematic review of 12 randomized trials in dialysis patients found that every trial showed a significant fall in blood phosphorus with nicotinamide [13]. In the NICOREN trial (100 people on haemodialysis, 24 weeks), nicotinamide lowered phosphorus about as much as the phosphate binder sevelamer (2.1 to 1.8 mM versus 2.3 to 1.7 mM), but only 55% of the nicotinamide group finished the trial versus 90% on sevelamer [14].

Doses used in studies

The skin-cancer trials used 500 mg of nicotinamide twice daily for 12 months [3][4]. In a kidney-transplant pilot, a run-in dose of 1,000 mg twice daily was cut to 500 mg twice daily because of gastrointestinal symptoms [9]. Creams contained 5% niacinamide applied twice daily for 12 weeks [1], or 2% niacinamide (with 2% tranexamic acid, twice daily for 8 weeks) [11].

Safety and interactions

Common side effects. A meta-analysis of randomized trials found nicotinamide increased digestive side effects, and a second found adverse events rare [6][2]. In ONTRAC there were no noteworthy differences in adverse events between nicotinamide and placebo at 500 mg twice daily [3]. In dialysis patients, flushing and diarrhoea were the most common problems, followed by low platelet counts (thrombocytopenia) [13], and in NICOREN only 55% completed 24 weeks of nicotinamide versus 90% on sevelamer [14].

Upper limits and toxic doses. The skin-cancer trials used 500 mg twice daily for a year without noteworthy differences in adverse events [3]. No upper intake limit was established in the studies reviewed.

Interactions. No data on interactions with medicines were found in the studies reviewed.

Pregnancy and breastfeeding. No data were found in the studies reviewed.

Relevant conditions. People on dialysis had more treatment stops and some cases of thrombocytopenia [14][13]. Organ-transplant recipients showed no skin-cancer benefit [4]. Nicotinamide does not replace sunscreen, which remains the foundation of skin cancer prevention [7]; anyone with a history of skin cancer should talk to a doctor before taking it.

Caveats and open questions

The skin cancer evidence rests mainly on one phase 3 trial, and the benefit did not continue after treatment stopped [3]. Meta-analyses disagree: one found the rate halved, another found insufficient evidence after pooling immunocompetent and immunosuppressed patients [6][2]. The veterans' study is observational, so it cannot prove cause and effect [8]. The skin-cream trials were short, mostly in small groups of women, and some tested combination products [1][11]. A recruiting phase 3 trial of nicotinamide in organ-transplant recipients (NCT05955924) is expected to finish in 2027.