American Melanoma Institute · 5 min read
What trials show about nicotinamide for preventing basal and squamous cell skin cancers, the usual dose, safety, and who may be offered it.
Nicotinamide is a form of vitamin B3 sold without a prescription, often under the name niacinamide. Over the past decade it has become one of the few pills with trial evidence for preventing the common skin cancers.
Vitamin B3 comes in 2 main forms. Niacin, also called nicotinic acid, is the form used in high doses to treat cholesterol. It causes flushing, a hot, red, prickly feeling in the face and chest, at doses as low as 30 to 50 milligrams. Nicotinamide has a slightly different chemical structure, does not cause flushing, and has no effect on cholesterol.
The skin cancer research used nicotinamide only. A bottle marked vitamin B3 may contain either form, so the ingredient line should read nicotinamide or niacinamide.
Laboratory work suggests how it might help. According to the trial investigators, nicotinamide improves the repair of DNA damaged by ultraviolet (UV) light and reduces the way UV suppresses immune defenses in the skin.
The main evidence is ONTRAC (Chen and colleagues, New England Journal of Medicine, 2015), a double-blind trial run in Sydney, Australia. It enrolled 386 adults who had each had at least 2 basal cell or squamous cell skin cancers in the previous 5 years. Participants took either nicotinamide 500 milligrams 2 times a day or a placebo for 12 months. Dermatologists examined everyone every 3 months.
After 12 months, the nicotinamide group had 23% fewer new skin cancers than the placebo group. Squamous cell carcinomas were down 30% and basal cell carcinomas 20%, although the basal cell result alone did not reach statistical significance. Actinic keratoses, the rough precancerous patches caused by sun damage, were 11% to 20% lower at each check. Side effects were no more common with nicotinamide than with placebo.
In the 6 months after participants stopped the pills, the difference between the groups disappeared. Nicotinamide seems to work only while a person keeps taking it.
ONTRAC had limits. The trial lasted 1 year, enrolled people at high risk in a very sunny country, and was not designed to study melanoma. No trial has shown that nicotinamide prevents melanoma.
Organ transplant recipients have very high rates of squamous cell carcinoma because of their anti-rejection medicines, so the same research group tested nicotinamide in them. ONTRANS (Allen and colleagues, New England Journal of Medicine, 2023) used the same dose for 12 months in recipients who had had at least 2 skin cancers.
The result was flat: 207 new skin cancers in the nicotinamide group and 210 in the placebo group. The trial enrolled 158 people and closed early because recruitment was slow, which left it with less statistical power than planned. A modest benefit can't be excluded.
In 2025, JAMA Dermatology published an analysis of Veterans Affairs health records (Breglio and colleagues). Researchers identified 12,287 patients who had filled prescriptions for nicotinamide 500 milligrams 2 times a day for more than 30 days and matched them with 21,479 similar patients who had not.
Nicotinamide users had a 14% lower risk of developing another skin cancer. Timing made a large difference. When nicotinamide was started after a first skin cancer, the reduction was 54%, and the benefit shrank when it was started after several cancers. The effect was strongest for squamous cell carcinoma. Among the 1,334 transplant recipients in the study, there was no significant reduction in skin cancers, which agrees with ONTRANS, though early use was linked to fewer squamous cell carcinomas.
This was an observational study. Patients were not randomly assigned, so people who took nicotinamide may have differed in ways the matching could not capture. Most were White men with an average age of 77. The findings support ONTRAC and suggest that earlier use may work better, and a randomized trial would be needed to confirm that.
Every major study used 500 milligrams 2 times a day, and that is the dose dermatologists suggest. The amount is far above the 14 to 16 milligrams a day the body needs as a vitamin, which makes this a drug-like use of a supplement.
At this dose, trial participants tolerated nicotinamide about as well as placebo. The NIH Office of Dietary Supplements notes that much larger amounts, around 3,000 milligrams a day, can cause nausea, vomiting, and signs of liver injury. In studies of people on dialysis, doses of 500 to 1,500 milligrams a day were linked to diarrhea and low platelet counts, so people with serious kidney disease need individual advice.
A newer question concerns the heart. A 2024 study in Nature Medicine (Ferrell and colleagues) found that heart patients with higher blood levels of 2 breakdown products of excess vitamin B3 had more heart attacks, strokes, and deaths over 3 years. That study measured blood markers and did not test nicotinamide supplements, so it does not show that the pills cause harm. The skin cancer trials reported no excess of side effects. More data is needed, and people with heart disease may want to raise the question with their doctor.
Most dermatologists who recommend nicotinamide do so for people who resemble the ONTRAC participants: adults with normal immune systems who have had 2 or more basal or squamous cell cancers, or who have many actinic keratoses. For transplant recipients, practice varies, and the randomized evidence does not support a benefit.
Nicotinamide does not replace sun protection or skin exams, and dermatologists do not advise it as a general supplement for people at average risk. A 23% reduction means that most skin cancers still occur.
