Science · October 2026 · 11 min

Niacinamide 2%, 5% or 10%, Honestly: Which Strength the Evidence Supports

Niacinamide is sold at anything from 2% to 20%, and the higher numbers usually cost more. The trials that built its reputation used 2% to 5%. We found one controlled trial at 10%, in a mixture, and none that compared 10% with 5%. Here is every strength that has been tested in people, and how to choose yours.

Solevia Niacinamide Gel Moisturiser, a 50 ml grey pump bottle with a white pump, next to its grey box on a light grey background

The short version

The strengths with the most clinical evidence are 2% to 5%. At 4–5%, trials found less visible dark spots and fine lines; at 2%, less oil and better-hydrated dry skin.
We found one controlled trial at 10%, and it tested niacinamide mixed with a vitamin C derivative and hyaluronic acid. It was well tolerated. We found no trial comparing 10% with 5%, and none at 20%.
In a 2025 laboratory study, 2.5%, 5%, 10% and 20% niacinamide changed the skin’s outer layer in the same way. In that test, more did not do more.
In safety testing, niacinamide caused no stinging at up to 10% and no irritation in use tests at up to 5%. If a high-strength product irritates you, try 5% before you give up on the ingredient.
Ours is 5%, the strength of the dark-spot and fine-line trials, in a gel with alcohol as its second ingredient: made for oily skin, wrong for dry or reactive skin.

If you came here to buy: our Niacinamide Gel Moisturiser is 5% niacinamide, €58.80, and qualifies for free shipping over €50 on its own. It suits oily and combination skin. If your skin is dry or reactive, read what is in ours first: it contains alcohol.

Niacinamide is sold at anything from 2% to 20%, and the bigger numbers usually cost more. It is natural to assume they work better. This is the honest version: every strength we could find tested in people, what each one did, and the point where the evidence stops, so you can choose a percentage on evidence rather than on the size of the number.

What percentage of niacinamide is effective?

In short: 2% to 5% is the range with the evidence. 5% niacinamide reduced the look of dark spots within 4 weeks and of fine lines and blotchiness over 12; 4% reduced wrinkles in one trial and improved melasma in another; 2% lowered oil and helped dry, atopic skin hold water. 10% has been tested in one controlled trial, as part of a mixture, and never against 5%.

Each of those results comes from comparing niacinamide with the same product without it, or with an established treatment. That is what makes them worth more than a before-and-after photo. The table lists every strength we found tested in people.

Every niacinamide strength we found tested in people

Strength	What was tested	People and length	Result	Lead researchers
2%	Oil (sebum)	100 people in Japan, 4 weeks; 30 in the US, 6 weeks	Lower sebum production in the first trial; less oil on the surface, but no change in production, in the second	University dermatologist
2%	Dry skin in atopic dermatitis, against petrolatum	28 people, forearms, 4–8 weeks	Less water loss and better hydration than petrolatum	University dermatology department, Japan
4%	Wrinkles around the eyes	30 Japanese women, split face, 8 weeks	Improvement in 64%, significantly better than the same cosmetic without niacinamide	University dermatology department, Japan
4%	Melasma, against 4% hydroquinone	27 people, split face, 8 weeks, with sunscreen	Both sides improved with no measured colour difference; good to excellent results in 44% vs 55%, side effects in 18% vs 29%	University hospital, Mexico
4%, as a medicine	Inflammatory acne, against 1% clindamycin gel	76 people, 8 weeks	Comparable to the antibiotic gel	University dermatology department, US
5%	Dark spots	18 Japanese women, 4 weeks	Less hyperpigmentation than the same moisturiser without niacinamide	Procter & Gamble
5%	Fine lines, spots, blotchiness, sallowness	50 women, split face, 12 weeks	Significant improvement on the niacinamide side, and better elasticity	Procter & Gamble
10%, with 5% magnesium ascorbyl phosphate and 5% hyaluronic acid	Melasma, against 4% hydroquinone	50 women, 60 days	Both improved with no significant difference; hydroquinone did numerically better; well tolerated	University dermatology departments, Brazil
20%	No trial found	No trial found	No trial found	No trial found

Two patterns stand out. The clearest effects on dark spots and lines come from 4–5%, used for 4 to 12 weeks. And several of the key trials were run by a company that sells niacinamide moisturisers, which is a reason to want independent confirmation. A 2021 university review that declared no conflicts of interest reached the same broad conclusion: topical niacinamide reduces the progression of skin ageing and hyperpigmentation, and is well tolerated.

Niacinamide 5% vs 10%: which is better?

Nobody has tested them against each other. We searched the clinical literature for a trial comparing 10% with 5% niacinamide and did not find one.

The one controlled trial of 10% we found, published in 2024 by two Brazilian university dermatology departments, used it in a mixture with 5% magnesium ascorbyl phosphate, a vitamin C derivative, and 5% hyaluronic acid. Fifty women with melasma applied either the mixture twice a day or 4% hydroquinone at night for 60 days. Both groups improved, with no significant difference between them, although hydroquinone did numerically better, and no serious side effects were found. So 10% in that formula was well tolerated and helped. Whether it beats 5%, that trial cannot say, and neither can any other we found.

The closest thing to a direct test of more is a 2025 laboratory study by Malmö University, with co-authors from the cosmetics company Oriflame. Researchers treated samples of the skin’s outer layer with 2.5%, 5%, 10% and 20% niacinamide. The effect on the layer’s structure was the same at every strength, and at the higher strengths the samples tended to hold more undissolved, crystalline niacinamide. That is isolated skin in a laboratory, not a face, but it is the only dose comparison we found, and more did not do more.

What a higher number reliably changes is the price, and how far you move from the strengths with the strongest tolerance data.

Is 10% niacinamide too much?

Not in the sense of being harmful for most skin. In the clinical tests collected by the Cosmetic Ingredient Review, niacinamide caused no stinging at up to 10% and no irritation in use tests at up to 5%, and it was neither a sensitiser nor a photosensitiser. EU law sets no maximum: niacinamide does not appear in any annex of the EU Cosmetics Regulation, so a 20% product is legal as long as its safety assessment supports it.

Too much for your skin is a different question. If a 10% or 20% serum has left you red, itchy or stinging, the likeliest causes are the rest of the formula, such as alcohol, fragrance or acids, or a barrier that is already irritated; our skin barrier guide covers that. Dropping to 5% in a simple formula is the cleanest test of whether niacinamide itself is the problem. We go through the other causes in why niacinamide stings.

For beginners and teenagers, there is no evidence that starting above 5% gains anything.

Niacinamide 2% vs 5%: is 2% enough?

For oil and for dry skin, 2% is the strength that was tested, and it worked. It lowered sebum in a trial of 100 people in Japan, though only partly in a second group in the US. And in 28 people with atopic dermatitis, a 2% cream on the forearms reduced water loss and improved hydration more than petrolatum did.

For dark spots and fine lines, the evidence starts at 4%. If you want one product for both, 5% sits inside the tested range for spots and lines, and above the 2% that lowered oil.

The best niacinamide percentage for your skin type

Which strength, by what you want it for

Your skin or goal	Strength with evidence	What to know
Oily skin and shine	2% upwards	2% lowered oil in one trial and partly in another. Expect less shine, not a different skin type. An oil-free gel suits the job.
Dark spots and uneven tone	4–5%	Changes at 4 weeks with 5% and at 8 weeks with 4%. Daily sunscreen matters more than the percentage.
Fine lines	4–5%	8 to 12 weeks in the trials, so judge it then, not before.
Dry or atopic-prone skin	2%, in a cream	Choose a rich, fragrance-free cream. An alcohol-based gel, including ours, is the wrong vehicle.
Sensitive skin	5% or less	The tolerance data is strongest at 5% and below. The rest of the formula matters more than the number.
Beginners	2–5%	No evidence that you gain anything by starting higher.
Acne	4%, tested as a medicine	A cosmetic moisturiser is not an acne treatment. Painful, cystic or scarring acne needs a doctor.
Melasma	4%, or 10% in a mixture	Both trials ran 8 to 9 weeks with sunscreen. Melasma is a skin condition, best managed with a dermatologist.

Why the number on the label is only half the story

How much niacinamide reaches your skin also depends on the formula around it. In a 2026 laboratory study, again from Malmö University with Oriflame co-authors, niacinamide passed through human skin about twice as readily from a neutral solution (pH 7.4) as from an acidic one (pH 5.0). Few brands publish their pH, so you cannot shop on it, but two products with the same percentage are not the same product.

The rest of the formula also decides how it feels. Alcohol, fragrance and exfoliating acids are all more likely to sting than niacinamide is at the strengths that have been tested.

And strengths do not add up neatly across products. We found no evidence that a niacinamide serum under a niacinamide moisturiser works better than one 5% product. What layering two does give you is two formulas that could irritate.

How to tell the percentage when the label does not say

Many brands do not state a percentage, and EU law does not require one. It does require an order: ingredients are listed in descending order of weight, and those below 1% may follow in any order after the rest. That gives you two useful clues.

Niacinamide high on the list, straight after water and the main base ingredients, is consistent with a strength of a few percent.
Niacinamide after phenoxyethanol, a preservative that EU law caps at 1%, means the niacinamide is almost certainly at 1% or less.
Ours: water, alcohol, then niacinamide, and we state the 5%.

That will not give you an exact figure. It will tell you when a product is selling the name of the ingredient rather than a meaningful amount of it.

What is in ours, and who should skip it

Our Niacinamide Gel Moisturiser is 5% niacinamide, the strength used in the trials on dark spots and fine lines, in thirteen ingredients. It is the only product we sell with niacinamide in it, and we do not sell a 10% or 20% version.

The honest part: alcohol is the second ingredient, listed ahead of the niacinamide, so the gel contains at least as much alcohol as niacinamide. That is what lets it dry down in seconds with nothing left on the surface, which is what oily skin wants under sunscreen. It is also why dry, tight or reactive skin should choose something else. The gel is lightly fragranced.

Dry or reactive skin: the Sensitive Skin Moisturiser, Fragrance Free (€58.80) has no fragrance and no ethanol. It does not contain niacinamide.
Dark spots: pair the gel with the Pigment Perfecting Serum (€45.60). Its alpha-arbutin acts on how much melanin skin makes; niacinamide reduces how much of it is passed on to surrounding skin cells, so the two work by different routes. The serum is fragranced and contains no niacinamide. We compared kojic acid and alpha-arbutin separately.

Unopened products can be returned within 14 days, with the return postage on us.

How to use 5% niacinamide

Cleanse gently, with a cleanser that does not leave your face feeling tight.
Apply a thin layer to clean, dry skin, morning and evening. The 12-week trial of 5% used it twice a day from the start; there is no need to build up.
SPF every morning. Niacinamide does not make skin sensitive to the sun, but UV drives the dark spots you are trying to fade. Ours is a tinted SPF50 stick.
Give it time: about 4 weeks for dark spots and 8 to 12 weeks for fine lines, judged in the same mirror and light.
One new active at a time, two weeks apart. For layering with vitamin C, acids and retinol alternatives, see what not to mix with niacinamide.

Questions we get asked

Is 5% niacinamide better than 10%?: Not on the evidence we found. 5% has the trials on dark spots and fine lines behind it, and no trial has compared it with 10%. The only controlled trial at 10% we found used it in a mixture with a vitamin C derivative and hyaluronic acid; it was well tolerated but did not beat 4% hydroquinone.
Is 2% niacinamide effective?: Yes, for what it was tested on: 2% lowered oil in one trial and partly in another, and a 2% cream improved hydration in dry, atopic skin more than petrolatum did. For dark spots and fine lines, the evidence is at 4–5%.
Is 10% niacinamide too much for beginners or sensitive skin?: It is not known to be harmful, since safety testing found no stinging at up to 10%. But there is no evidence that a beginner gains anything over 5%, and the tolerance data is strongest at 5% and below. With sensitive skin, start at 5% or less, in a fragrance-free formula.
Is 20% niacinamide safe?: We found no published clinical trial at 20%, and the stinging data in the safety assessment goes up to 10%. No data is not the same as unsafe, and EU law sets no maximum, but there is also no evidence that 20% does more than 5%.
What percentage of niacinamide is best for hyperpigmentation?: 4–5% in the trials. 5% reduced the look of dark spots within 4 weeks, and 4% performed close to 4% hydroquinone for melasma over 8 weeks, with sunscreen. Daily sunscreen is not optional: UV undoes the work.
What percentage of niacinamide is best for oily skin?: 2% lowered sebum in one trial and partly in another, and 5% is within the range tested for other benefits. The format matters as much as the number: an oil-free gel suits oily skin better than a rich cream.
Can I use two niacinamide products together?: You can, but we found no evidence that a niacinamide serum plus a niacinamide moisturiser works better than one 5% product, and every extra formula is another chance of irritation.
Is niacinamide 500 mg the same as niacinamide in skincare?: No. Tablets are measured in milligrams and swallowed; skincare is measured in percent and applied. In an Australian trial, 500 mg of oral nicotinamide twice a day for a year cut new non-melanoma skin cancers by 23% in people who had already had at least two. A later trial in organ-transplant recipients found no benefit. Taking it is a medical decision, for a doctor, not a skincare choice.
Does EU law limit niacinamide?: No. Niacinamide is not listed in any annex of the EU Cosmetics Regulation, so there is no legal maximum concentration. Like every cosmetic, a niacinamide product still needs a safety assessment before it can be sold.

Where to start

If your skin is oily or combination, start with 5%: it is the strength with the trials behind it, and there is no evidence that 10% or 20% does more. Our Niacinamide Gel Moisturiser is 5% in a weightless gel; use it twice a day for twelve weeks, with SPF every morning. For dark spots, see the brightening and dark spot edit; for oily skin, our comparison of zinc PCA and niacinamide.

If your skin is dry or easily upset, a percentage will not fix the wrong formula. Choose a fragrance-free cream first, and add niacinamide later if you still want it.