Nicotinamide dosage and evidence
Written by Aaron CuhaReviewed Sep 2026
The short answer
Nicotinamide is a plain form of vitamin B3.
Evidence grade for Nicotinamide: Moderate. The rule: at least one finished study in people, and at least 100 people who took it. The sum on this page: 4 completed trials, 591 people given it. A grade counts how much has been done to people, not whether it works.
- People given it
- 591
- Human studies
- 4
- Found nothing
- 4
Dose
No human dose established
Amounts that were given in studies sit in Human evidence on this page. None of them is a personal dose.
4 completed trials, 591 people given it
2 effects reported, 1 unwanted, 1 wanted, by people using it, not a trial
Goal pages: Brain, memory and mood, Ageing and longevity, Heart and circulation, Sleep
In plain English
In plain English, from Aaron
This is how I would explain it to a friend. The evidence, with the numbers, is further down the page.
Nicotinamide is a plain form of vitamin B3. It is cheap and sold over the counter. It does not cause the flush that niacin does. It is the one NAD product with a real win in a big study, and that win is about skin cancer.
What people take it for
- Fewer new skin cancers in people who keep getting them.
- Raising NAD to slow ageing.
- Skin care, in creams.
What studies in people showed
In 552 people at risk of type 1 diabetes, five years of high doses did nothing to stop it. In 386 people who kept getting skin cancers, 500 mg twice a day cut new ones by 23 percent over a year. The benefit stopped when the pills stopped. The same plan in 158 transplant patients found no difference. In 65 healthy adults, it did not keep blood NAD raised. No study has tested it against ageing.
What people report
Reports, not study results
The good
- In the big studies, side effects were no different from the dummy pill, even over five years.
The bad
- In the kidney study, stomach upset made it hard for people to keep taking it.
Where these come from: We have no user reports. These lines come from the studies on this page.
My bottom line
If you have had repeat skin cancers, ask your skin doctor about it. For raising NAD or living longer, the evidence is not there.
An opinion, not a finding. I am a coach, not a doctor.
What it has been measured to do
Measured in people
Goals Nicotinamide has been tested for in people, biggest studies first. We count only what the studies on this page say, so the real numbers may be higher.
- Kidney function205 people · 1 study · 1 found nothing
- Mood and anxietyno headcount stated · 1 study · 1 found nothing
Animal and lab work, not yet tested in people
Real results, but from animals or cells, not people. What works in a mouse often does not work the same way in a person. Nobody can patent this, so nobody would ever earn back the cost of a study in people. That is usually why there is none. The record on this one is set out below.
- Living longer1 animal or lab study
33 of the 36 indexed goals have no study of any kind behind Nicotinamide
No study in people, animals or cells on this page reports a result for these. That does not prove Nicotinamide does nothing for them. It does mean anything you have heard about Nicotinamide and one of these did not come from a study cited here.
Show full evidence
What is Nicotinamide?
Nicotinamide is a plain form of vitamin B3. In a large final-stage study of 386 people at high risk, 500 mg twice a day cut new skin cancers other than melanoma by 23 percent over 12 months. The benefit stopped once the pills stopped. The same study in 158 organ transplant patients found nothing. No study has ever tested it against ageing.
Nicotinamide is the cheapest thing in this whole group. It is also the only NAD-pathway product with a winning large final-stage study on a health result a patient would notice. That result is about skin cancer, not ageing. That difference matters more than anything else on this page.
Every time a cell uses up an NAD molecule, nicotinamide is left over. The enzymes that use up NAD include the sirtuins, PARP and CD38. So nicotinamide is not just something you feed in from outside. It is the leftover from using NAD, and the body keeps recycling it back into NAD with an enzyme called NAMPT. That closed loop is why nicotinamide acts differently from the riboside and NMN forms, which sell for a hundred times the price.
The most direct test in people found exactly that. 65 healthy adults took one of three NAD boosters for 14 days, and everyone knew which. Nicotinamide riboside and NMN raised NAD in the blood by about the same amount. Plain nicotinamide did not keep it raised, though it did cause a short-lived shift in NAD-related chemicals in the blood. If you want blood NAD to go up and stay up, nicotinamide is not the one that does it.
What nicotinamide does do is feed DNA repair in skin damaged by the sun. It also eases the way sunlight weakens the skin's immune defence. That is what sits behind the skin cancer result. And it runs out when you stop taking it.
There is also a real problem in theory for anyone taking it to live longer. Nicotinamide directly blocks sirtuins, the enzymes the whole NAD story is built on. That has been shown with purified enzymes at normal body levels. In yeast, high nicotinamide cut lifespan down to that of yeast with no sirtuin at all. Nobody has shown this happens in a person taking a supplement. Nobody has shown it does not.
How does Nicotinamide work?
Nicotinamide is turned back into NAD by the recycling route. First an enzyme called NAMPT turns it into NMN. Then other enzymes turn NMN into NAD. NAMPT is the slow step. So more nicotinamide does not mean more NAD in a straight line. The bottleneck is the enzyme, not the supply. Separately, nicotinamide is what is left when sirtuins, PARPs and CD38 use up NAD. It then blocks sirtuins by sitting in a pocket next to where NAD binds, which switches the enzyme away from its normal job. In skin, the cancer-prevention effect works a different way again and does not depend on NAD in the blood at all. Nicotinamide helps repair DNA damaged by sunlight, and it eases the way sunlight weakens the skin's immune defence.
What have studies in people found about Nicotinamide?
Unusually good for a vitamin, and almost all of it is about something other than ageing. Two large skin cancer studies, one 5-year diabetes prevention study and one 12-month kidney study. Well over a thousand people in all.
- ENDIT, 552 people, 5 years at 1.2 g per square metre of body surface: it did nothing to stop type 1 diabetes. People on the dummy pill did just as well.
- ONTRAC, 386 people, 12 months: 23 percent fewer new skin cancers other than melanoma, and no benefit after stopping.
- COMBINE, 205 people with kidney disease, 12 months at 750 mg twice a day: no effect on blood phosphate or the hormone that tracks it.
- ONTRANS, 158 transplant patients, 12 months: no difference at all. It was stopped early because too few people joined, so it was also too small to reliably spot the effect it was looking for.
- A test of three NAD boosters in 65 healthy adults over 14 days: plain nicotinamide did not keep blood NAD raised. Nicotinamide riboside and NMN did.
- No study in people has measured lifespan, healthy years, thinking, muscle function or any ageing outcome with nicotinamide.
What this does not tell you: The one winning result only applies to certain people, and it works one specific way. ONTRAC took people who had had at least two skin cancers other than melanoma in five years. That is a heavily sun-damaged group. The effect was gone within the six months after stopping. It says nothing about a person with ordinary skin, about melanoma, or about ageing. ONTRANS was stopped because too few people joined, not because it was clearly failing. So it is a failed repeat in a different group, not a clean disproof. Nothing here supports taking nicotinamide to raise blood NAD. The direct comparison says it does not keep it raised.
The state of the research
Almost all consumer writing about this pathway blends three kinds of claim into one. Keeping them apart is most of the work. A blood marker claim says a product raises NAD in the blood. That is easy to show, and for several of these products it is simply true. A middle claim says it moves something between a blood marker and a symptom, such as how stiff the arteries are. A health claim says a person walks further, remembers more, gets fewer cancers or lives longer. A product can be solid on the first kind and have nothing at all on the third. That is where most of this pathway sits. No published study in people of any NAD booster has shown a real health benefit, with one exception on this list. That exception is nicotinamide in skin cancer. It works by helping sun-damaged skin repair its DNA, not through anything to do with ageing.
The sirtuin question is the awkward one for anyone selling nicotinamide to help you live longer. The whole NAD story rests on sirtuins needing NAD to work. Nicotinamide is what those enzymes give off when they work, and it turns around and blocks them. That block is real and well understood in purified enzymes, at levels the papers call normal for the body. In yeast, the effect on lifespan was large and in the wrong direction. What is missing is any measure of sirtuin activity in a person taking nicotinamide at supplement doses. The honest statement is this. The block exists. Whether it matters at the doses people swallow is unknown. And the product is being sold on an idea that its own chemistry partly works against.
There is also a bottleneck in the recycling route. The enzyme NAMPT is the slow step in turning nicotinamide into NMN and then NAD. Pouring in more of what a maxed-out enzyme uses is not the same as getting more of what it makes. That is the most likely reason nicotinamide did not keep blood NAD raised in the head-to-head test, while the two forms that skip NAMPT did.
The evidence, in charts
Fig. 1a · how many people
591people, across 2 studies in people cited here
| Study | People | Share |
|---|---|---|
| New England Journal of Medicine 2015 | 386 | 65% |
| Journal of the American Society of Nephrology 2019 | 205 | 35% |
One study holds 65% of these people, so the total rests more on one study than its size suggests. Counts are the number of people each study on this page says it signed up. That includes studies that only watched people and gave nobody the compound. 2 more studies in people give no headcount and are not counted here. Studies still signing people up are left out, and only studies cited on this page are counted.
Fig. 1b · evidence mix
4 of 5 sources here are studies in people. The rest is not.
- Study in people · done in people480%
- Lab (cells in a dish) · cells or tissue120%
Counted from the list of sources on this page. It counts only what we cite, so there may be more studies out there. A review counts once, however many studies it sums up.
Fig. 2 · evidence over time
The studies cover 5 different years, 2002 to 2023, counted from the list of sources on this page.
Fig. 3 · legal status at a glance
US
Not approved
UK
Not approved
AU
Not approved
CA
Not approved
Not approved in any of the four countries shown. This is what the law says, not a verdict on the science. See Legal status below for the full text and any notes.
Fig. 4 · how much does what
Nobody has tested different amounts in people
This chart would show how the effect changes as the amount goes up. For this compound, nobody has measured that in people. So we leave it empty. We will not borrow an animal chart and pretend it works the same in people.
Fig. 5 · what the molecule is
- Kind of compound
- Supplement
- Molecule weight
- 122.1 Da
- Half-life
- About 4 hoursShort, 1 to 6 hours
- Chain length
- None on file
Half-life as stated on file: About 4 hours in plasma, which is why the skin cancer trials dosed it twice a day rather than once.
No amino acid sequence is on file for Nicotinamide, which is expected: a supplement is not built from amino acids.
The studies we cite
- Study in people2015A Phase 3 Randomized Trial of Nicotinamide for Skin-Cancer Chemoprevention
Vitamin B3 cut new skin cancers in people who keep getting them, and the protection stopped when the pills stopped. 386 people who had had at least two skin cancers in five years took nicotinamide twice a day or a dummy pill for a year, and nobody involved knew which. New skin cancers came about a quarter less often on the vitamin. Split by cancer type, the separate counts were too small to be sure. Side effects matched the dummy. Once people stopped taking it, the benefit went. Publicly funded.
ONTRAC. 386 people who had had at least two non-melanoma skin cancers in the previous 5 years were randomised 1:1 to nicotinamide 500 mg twice daily or placebo for 12 months. The rate of new non-melanoma skin cancers at 12 months was 23 percent lower with nicotinamide (95 percent CI 4 to 38, P=0.02). Basal-cell carcinomas were 20 percent lower (95 percent CI -6 to 39, P=0.12) and squamous-cell carcinomas 30 percent lower (95 percent CI 0 to 51, P=0.05), so only the combined endpoint was clearly significant. Actinic keratoses were 13 percent lower at 12 months. Adverse events did not differ from placebo. The paper states there was no evidence of benefit after nicotinamide was discontinued. Funded by the National Health and Medical Research Council.
- Study in people2023Nicotinamide for Skin-Cancer Chemoprevention in Transplant Recipients
The same team tried to repeat the skin cancer result in transplant patients and it did not work. 158 organ transplant recipients who already had repeated skin cancers took the same dose for a year. New cancers came up 207 times on the vitamin and 210 times on the dummy pill, which is no difference at all. Nothing changed in either cancer type, in sun damaged patches, or in quality of life. The trial closed early because too few people joined, so it is smaller than planned.
ONTRANS, the replication attempt by the same group in a higher-risk population. 158 organ-transplant recipients with at least two keratinocyte cancers in the previous 5 years, randomised 1:1 to the same 500 mg twice daily for 12 months. The trial was stopped early for poor recruitment. There were 207 new keratinocyte cancers on nicotinamide and 210 on placebo, rate ratio 1.0 (95 percent CI 0.8 to 1.3, P=0.96). No difference in squamous-cell or basal-cell counts, actinic keratoses or quality of life.
- Study in people2004European Nicotinamide Diabetes Intervention Trial (ENDIT): a randomised controlled trial of intervention before the onset of type 1 diabetes
The longest trial this vitamin has ever been given was run to prevent type 1 diabetes, and it failed. 552 close relatives of people with type 1 diabetes, all carrying the antibodies that predict it, took high dose nicotinamide or a dummy pill for five years. 159 developed diabetes, 82 on the vitamin and 77 on the dummy. Serious side effects were no different, so this is also the best evidence that years of high doses are tolerated. A strong animal result did not survive a proper human test.
The largest long-duration nicotinamide trial ever run, and it was negative. 552 first-degree relatives with confirmed islet-cell antibodies received modified-release nicotinamide at 1.2 g per square metre or placebo for 5 years. 159 developed diabetes, 82 on nicotinamide and 77 on placebo, unadjusted hazard ratio 1.07 (95 percent CI 0.78 to 1.45, P=0.69). Serious adverse events did not differ. This is the trial that establishes what multi-year high-dose nicotinamide safety looks like, and that a strong animal rationale does not survive a properly powered human test.
- Study in people2019Effects of Nicotinamide and Lanthanum Carbonate on Serum Phosphate and Fibroblast Growth Factor-23 in CKD: The COMBINE Trial
Nicotinamide did not do what this kidney trial asked of it. 205 people with fairly advanced kidney disease took nicotinamide, a phosphate binder, both, or two dummy pills for a year. Neither drug meaningfully lowered blood phosphate or the hormone that tracks with it, which were the two things the trial was built to move. Side effects were similar across groups, but stomach upset made it hard for people to keep taking the pills. The funding was independent of any manufacturer.
205 people with stage 3b or 4 chronic kidney disease randomised to nicotinamide 750 mg twice daily, lanthanum carbonate, both, or double placebo for 12 months. Neither drug significantly lowered serum phosphate or intact FGF23, the dual primary endpoints. Adverse event rates were similar across arms but gastrointestinal symptoms limited adherence. Another well-run, independently funded, multi-year nicotinamide trial that missed its primary endpoint.
- Lab (cells in a dish)2002Inhibition of silencing and accelerated aging by nicotinamide, a putative negative regulator of yeast sir2 and human SIRT1
In a dish and in yeast. At normal body levels, nicotinamide blocked the yeast sirtuin and the human sirtuin SIRT1, about as well as the best man-made blockers. In yeast, it switched off gene silencing and cut lifespan to that of yeast with no sirtuin. Nobody has shown this happens in a person taking a supplement, or that it does not.
Purified enzyme and yeast work. Physiological concentrations of nicotinamide non-competitively inhibited both yeast Sir2 and human SIRT1 in vitro, with an IC50 below 50 micromolar, which the authors describe as equal to or better than the best synthetic inhibitors of the class. In yeast, nicotinamide abolished silencing, increased rDNA recombination and shortened replicative lifespan to that of a sir2 mutant. This is yeast and test-tube data. It has never been shown to occur in a person taking a supplement, and it has never been shown not to.
Common questions
Has Nicotinamide been tested in people?
Yes. 591 people given it across 4 completed trials cited here, 4 of which found nothing. Nicotinamide is a plain form of vitamin B3.
What is the Nicotinamide dosage?
No human dose established. Amounts that were given in studies sit in Human evidence on this page. None of them is a personal dose. 4 completed trials, 591 people given it
Is Nicotinamide FDA-approved?
Not an approved drug for preventing skin cancer in the United States. It is a standard form of the vitamin niacin. It is sold over the counter and found in multivitamins and skin care products. The dose used in the ONTRAC study is an over-the-counter dose, used off label, meaning outside any approved use.
Is nicotinamide the same as niacin?
They are both vitamin B3, and you cannot swap one for the other. Nicotinamide does not cause flushing. Nicotinic acid, usually just called niacin, does cause flushing, through a receptor called GPR109A. It also changes blood fats, which nicotinamide does not. The big heart studies that found nothing were run with nicotinic acid, not nicotinamide.
Does nicotinamide raise NAD?
Not for long, on the best direct test there is. In 65 healthy adults over 14 days, nicotinamide riboside and NMN raised blood NAD by about the same amount, and nicotinamide did not. It did cause a short-lived shift in NAD-related chemicals in the blood. The likely reason is that the recycling enzyme NAMPT is the slow step. Adding more of what it uses does not speed up an enzyme that is already maxed out.
Should I take nicotinamide to prevent skin cancer?
That is a talk to have with a skin doctor. The honest summary is this. In people who have already had at least two skin cancers other than melanoma in five years, 500 mg twice a day cut new ones by 23 percent over 12 months. That was a large final-stage study of 386 people. The benefit stopped when the pills stopped. The same plan in 158 organ transplant patients found no effect at all. There is no evidence for it in people without that history.
Does nicotinamide block sirtuins?
With purified enzymes, yes, at levels the authors call normal for the body. In yeast it cut lifespan to that of yeast with no sirtuin at all. Whether that happens in a person taking a pill has never been measured. It is a real open question, not a settled objection. A supplement sold on switching sirtuins on should have to answer it.
Is high-dose nicotinamide safe?
Its safety record over years is better than almost anything else in this group. ENDIT gave 552 people 1.2 g per square metre of body surface for five years, and serious side effects were no different from the dummy pill. ONTRAC gave 500 mg twice a day for a year, with side effects no different from the dummy pill. Liver damage has been seen at gram-level doses of the acid form, nicotinic acid, not the amide. None of that safety record covers anyone with an active cancer, because those studies left them out.
Will it help me live longer?
There is no evidence either way, because no study has ever asked. Every study of nicotinamide in people has measured skin cancers, diabetes onset, or kidney blood tests. Lifespan, healthy years and thinking have never been measured.