Experts Debunked the Viral TikTok Vitamin C Test—Here's What to Look for Instead

We asked the pros to weigh in.

Serum dropper and bottle

Tawni Bannister / Byrdie

When it comes to skincare ingredients, vitamin C is one of the most popular (and one of the most highly debated) options out there. Yes, it's been proven to offer a host of skin benefits (it stimulates collagen production, lightens dark spots, and protects against oxidative damage). Still, not all vitamin C serums are created equal. First, there's the fact that the ingredient is highly unstable and can lose its potency if exposed to heat, light, and air. Then, there's the matter of finding just the right concentration of vitamin C to maximize a product's efficacy (not too little, not too much). 

It can still sometimes feel like a gamble when shopping for vitamin C products—especially when there are so many offerings on the market. So, when we came across a TikTok user who claims to have found a fast, easy, and DIY way to test which vitamin C serums are actually worth the investment, we were both intrigued and skeptical. To find out more, we turned to two dermatologists and a cosmetic chemist to get their take on the viral test. Keep reading to see whether TikTok's vitamin C test holds up, and find out how else you can see if a serum works before you buy.

Meet the Expert

The Test

Late last month, a TikTok user's DIY vitamin C experiment started gaining traction on the app. In the videos, which have since racked up millions of views, the user claims you can test a vitamin C serum's effectiveness by mixing it with a standard first aid kit staple: antiseptic solution. 

She combines a glass of water with a capful of antiseptic to conduct the test, turning the water coffee-brown. Then, she adds a few drops of a vitamin C serum to the glass (in her first viral iteration, she chooses three popular offerings: the Korres Wild Rose Spotless Serum ($68), the Josie Maran Argan Bright Skin Vitamin C Serum ($65), and the Paula's Choice C15 Super Booster ($49)).

If you're already cringing at the wasted product, just wait because this is when the "magic" happens. After she stirs all three glasses, the Korres and Josie Maran concoctions remain brown, but the glass with Paula's Choice serum miraculously returns to its pre-antiseptic clear color. According to the user, if the solution turns clear, it indicates that the serum contains vitamin C. If the solution remains brown, it's supposedly lacking the all-important ingredient. Unfortunately, things are never as simple as they seem on social media.

I'll admit: upon my first viewing, I was immediately transfixed by the test's potential, as were the TikTok users who flooded the comment section with requests to test their go-to vitamin C next. The user obliged and repeated the experiment with other serums, all with varying results. The cult-favorite Mario Badescu Vitamin C serum? No dice—the mixture stayed brown. The drugstore staple serum from La Roche Posay? A winner! The solution turned crystal clear when mixed with antiseptic. The eternally popular indie pick from Mad Hippie? Luckily for its legion of loyal fans, it passed, too.

Since the initial TikTok went viral, users across the app have tried out the experiment themselves to see if their favorites passed the test. As is par for the course with any viral TikTok trend, there’s been quite the debate going on in the comments about whether the test is even accurate in the first place. To see if the DIY experiment holds up, I reached out to a handful of experts to ask the same question: could finding an effective vitamin C serum be this simple?

What the Experts Say

In short, not quite. As noted in a TikTok from Javon Ford, an LA-based cosmetic chemist, the test is “pointless” for determining the efficacy of a vitamin C serum since it’s the presence of ascorbic acid—not vitamin C—that causes the mixture to turn clear. Ascorbic acid is a common (though highly unstable) form of vitamin C, and as Ford points out, only Paula’s Choice from the original viral TikTok contains it, which explains why the mixture turned clear.

“The serums being tested are using two different versions of Vitamin C,” says Dr. Corey L. Hartman, a board-certified dermatologist and the founder of Skin Wellness Dermatology in Birmingham, AL. “It’s like comparing apples to oranges, and also a waste of all three perfectly good products.”

Krupa Koestline, a cosmetic chemist and the founder of KKT Consultants, agrees. “This is a good at-home test to check for the presence of ascorbic acid,” she tells us. “However, a lot of brands rely on more stable forms of Vitamin C, or Vitamin C derivatives, in their products, which would not produce the same results in these tests, despite containing high amounts of vitamin C derivatives.”

Bottom line, the DIY experiment can't actually tell you if a serum contains vitamin C or not, since it only tests for one form of the ingredient. However, while this viral TikTok test might not live up to the hype, the experts did recommend a few other qualities to look out for when searching for the best vitamin C products on the market.

What to Look For

The Concentration

While it’s natural to assume that a higher concentration of vitamin C makes for a more effective product, that’s not entirely the case, says Dr. Stacy Chimento, a board-certified dermatologist based in Miami. “For any vitamin C product to be effective, the concentration should be between 8 and 20 percent,” she explains. “Anything less is ineffective, while anything above it can begin to dwindle.” Chimento recommends the La Roche-Posay Vitamin C Serum ($42), which contains a concentration of 10 percent pure vitamin C to boost radiance.

La Roche-Posay Pure Vitamin C Face Serum
La Roche-Posay Pure Vitamin C Face Serum $42
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The Packaging

According to the experts, the bottle that holds your vitamin C serum can actually affect how well it works. “The packaging may seem like a minuscule factor, but the reality is that the bottle should be dark or even slightly opaque to avoid light exposure,” says Chimento. “The cap should also be tight to prevent premature oxidation.” Koestline agrees that an opaque, air-restrictive bottle or pump container is ideal for ensuring that ingredients remain staple: “A vitamin C cream that comes in a jar, unfortunately, won’t remain effective for long.”

Vitamin C serum

Liz deSousa / Byrdie

The Added Ingredients

"The presence of other ingredients can make or break whether a vitamin C serum is effective or not,” Chimento explains. “Ingredients like vitamin E or ferulic acid can stabilize vitamin C and strengthen the antioxidant reaction while being gentler on the skin."

Koestline agrees that one of the most effective ways to increase the potency of a vitamin C product is to combine it with other antioxidants. “There have been several studies that have proven the combination of antioxidants works better than just vitamin C alone,” she says. One of her current favorites is the Allies of Skin 35% Vitamin C Perfecting Serum ($118), a waterless formula that’s made with two different vitamin C derivatives, superoxide dismutase, and glutathione. “It’s a simple, yet effective product,” says Koestline.

Allies of Skin 35% Vitamin C Perfecting Serum
Allies of Skin 35% Vitamin C Perfecting Serum $118
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The Formula

From serums to oils to creams, there are a plethora of different vitamin C products to choose from. According to Hartman, however, one type of formula rises above the rest when it comes to effectiveness.

“Choose a vitamin C serum over a moisturizer,” he recommends. “A serum absorbs deeper into the dermis where fibroblasts that produce collagen and elastin reside.” Plus, Hartman adds, the molecular size of a serum lends itself to better penetration and absorption than a lotion or a moisturizer. His top picks include the best-selling SkinCeuticals C E Ferulic ($166), which he calls the “gold standard” of vitamin C serums, and the Heraux Molecular Anti-Inflammaging Serum ($250), which combines vitamin C with a “potent cocktail” of ingredients for firm, plump, and smooth skin.

Heraux Molecular Anti-Inflammaging Serum
Heraux Molecular Anti-Inflammaging Serum $250
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The Results

While it might not be the fastest method, waiting to see visible results is undeniably one of the most effective ways to tell if your vitamin C serum is working. Chimento says that with time, you should start to notice a more even skin tone and a reduction in the appearance of wrinkles and fine lines.

"The best way to tell if your product is effective is to use it over an extended period (about three months) and note any changes in your skin and any reactions you may have," she explains. "If not, you should consider meeting with your dermatologist to discuss changing your product for something more potent and effective."

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