We Ask a Chemist: What Percentage Vitamin C Serum Is Best?

What Percentage Vitamin C Is Best: Photo of a woman dropping skincare serum into her palm
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By now, many of you are familiar with the benefits of using vitamin C in your skincare routine. (As a quick refresher, it’s a potent antioxidant that’s known to brighten skin, fight against free radical damage and promote collagen production.)

Given its popularity, there is an abundance of options to choose from, and one of the questions that comes up most when shopping for a vitamin C product is what percentage is best?

Is a Higher Percentage of Vitamin C Better?

According to Victoria Fu, a cosmetic chemist in residence at Revela, and the co-founder of Chemist Confessions, no. “You can actually use as little as five percent L-ascorbic acid to reap the benefits. I know people are used to hearing about products with as much as 20 percent, but there’s definitely some skin types that don’t do well with that much ascorbic acid, and often deal with signs of irritation like redness and itchiness as a result,” she explains. (Note: There are other vitamin C derivatives like ascorbyl glucoside and THD ascorbate that can also be found in skincare products, which may be more suitable if your skin doesn't tolerate asorbic acid, but they been studied as much.)

What Is the Best Percentage of Vitamin C to Look For?

The target concentration of ascorbic acid you’ll most often find in products is between five and 20 percent. You may have heard that 10 percent is “the golden number,” but that’s just a guestimate since it’s the average of that 5 to 20 percent range you see on the market.

Again, Fu reiterates that “more doesn't always mean better, especially if it causes irritation.” So rather than focus solely on the percentage of vitamin C in a product, she recommends paying closer attention to the way it's formatted because that will also affect how it’s used in your routine.

On that note, you can find ascorbic acid in three different formats: water-based serums, powders and anhydrous suspensions, all of which have their pros and cons (illustrated above).

To quickly recap, the main pros of a water-based serum is that it's the OG, and the most tested with clinical studies. However, they have the shortest shelf-life of the three. Powders are the most stable, but they can be messy, and anhydrous suspensions offer more stability than a water-based serum, but can have inconsistent formulas (some have a gritty texture, which should be avoided).

Of the three, “water-based serums are the classic way to go,” says Fu, who adds that you want to store these serums in vampire settings (i.e., in cold, dark places) and be mindful of their shelf life.

Regardless of the percentage or format you choose, remember that consistency is key. Vitamin C should be used every morning, after cleansing and before any moisturizer or sunscreen.

Jenny Jin Headshot Vertical 2023

Beauty Director

Jenny Jin is PureWow’s Beauty Director and is currently based in Los Angeles. Since beginning her journalism career at Real Simple magazine, she has become a human encyclopedia of...