We independently evaluate all recommended products and services. If you click on links we provide, we may receive compensation. Learn more. Shopping People Tested The 15 Best Vitamin C Serums of 2024 That PEOPLE Tested We've never gotten so many compliments on our skin. By Bianca Lambert Bianca Lambert Bianca Lambert has been writing for PEOPLE since 2022. She is also a contributing writer for Byrdie specializing in natural hair and skincare. She has worked as a freelance beauty and travel writer for over four years. Bianca graduated with a degree in Television Broadcasting from Middle Tennessee State University. She started her career at BuzzFeed in Los Angeles, where she worked as a Style and Beauty Video Producer, before taking a role as Social Video Coordinator. After two years in the world of video, she currently resides in Los Angeles and works as a freelance writer and creative producer. People Editorial Guidelines and Cai Cramer Cai Cramer Cai Cramer is a shopping writer at PEOPLE.com with 2 years’ experience in journalism and digital media. She regularly tests the best and buzziest products in the beauty and lifestyle spaces and has researched and written about moisturizers, blow dryers, clothing, and luggage, among many other popular products. People Editorial Guidelines Updated on April 26, 2024 05:15AM EDT In This Article Expand Jump to a Section Our top picks Reviews What to Know Behind the Scenes FAQ Why Trust PEOPLE? What Is People Tested? People / Kristin Kempa Vitamin C is one of the most searched skincare ingredients on the internet. Rightfully so, given the number of products on the market and the fact that the powerhouse ingredient actually yields visible results. The More You Know Vitamin C is clinically proven to protect against sun damage while boosting collagen and minimizing wrinkles — making it a popular active ingredient in eye serums and other skincare products. "Translated to real life, vitamin C is a workhorse for looking great," Dr. Christina Lee Chung, board-certified dermatologist at Schweiger Dermatology Group, tells PEOPLE. However, to get benefits like improving wrinkles, evening out skin tone, and helping with skin sagging, Chung says consistency is key — so using vitamin C daily can be a game-changer for your skin. PEOPLE tested 32 vitamin C serums for six weeks, and, honestly, we were blown away by the brightening and firming abilities of these skincare products. Our Top Picks Best Overall: L'Oreal Paris Revitalift Vitamin C Face Serum at Target ($27) Jump to Review Best Overall, Runner-Up: SkinCeuticals C E Ferulic at Dermstore ($182) Jump to Review Best Budget: Yes To Grapefruit Brightening Serum at Amazon ($15) Jump to Review Best for Fighting Sun Damage: Herbivore Brightening Serum at Sephora ($65) Jump to Review Best for Mature Skin: Klur Brilliant Light Repair Serum at Klur.co (See Price) Jump to Review Best for All Skin Tones: BeautyStat Universal C Skin Refiner at Amazon ($85) Jump to Review Best for Immediate Glow: Olay Vitamin C Peptide 24 Serum at Target ($30) Jump to Review Best for Dark Spots: Goodal Vitamin C Dark Spot Serum+ at Target ($27) Jump to Review Best for Sensitive Skin: CeraVe Skin Renewing Vitamin C Serum at Amazon ($18) Jump to Review Best for Dry Skin: Sephora Collection Super Glow Serum with Vitamin C+E at Sephora ($21) Jump to Review Best Overall L'Oreal Paris Revitalift Vitamin C Face Serum Target View On Target $27 View On Walgreens $36 View On Lorealparisusa.com Pros Just as effective as products that are double the price Drastically improved our skin over the course of a few months Tube shape allows you to get every last drop Glides onto the skin easily without feeling sticky or weighed down Cons Results weren’t immediate, but we did notice them over time Drugstore products are competing with pricier options and becoming best in class. This fragrance-free anti-aging serum features 10 percent vitamin C, with over 3,500 users giving five-star ratings of the fast-absorbing, skin-mattifying formula after seeing visible results. During our tests, we found that while the serum didn’t yield immediate results like other serums we tried, it offered longer-lasting results. Over the course of a few months, this L'Oreal serum drastically improved our tester's skin's radiance. “I've paid this much for other vitamin C serums that were half as effective, so I think this is a great price for this product," she said. On top of that, this serum melted into the skin without any stickiness or added weight and had an immediate glowing and smoothing effect. Plus, unlike pump containers, the L'Oreal Revitalift tube shape prevents you from wasting any serum because you can squeeze every last drop out of this affordable product. Size: 1 oz. | Star Ingredients: 10% vitamin C, hyaluronic acid, retinol | Skin Type: All People / Samantha Jones Pro Tip! Stick with a 10 percent vitamin C concentration if this is your first experience with the antioxidant or if you have sensitive or reactive skin. You can always work your way up to a higher concentration. Best Overall, Runner-Up SkinCeuticals C E Ferulic Bluemercury View On Dermstore $182 View On Skinstore.com $272 View On Skinceuticals.com $182 Pros Improves skin texture while also boosting radiance Works well with other skincare products that might already be part of your routine Doesn't leave a sticky residue Glowing and smoothing effects were noticeable Cons It has an odd sour-like scent upon application If you ask anyone serious about their skincare routine, it's very likely this is (or has been) in their rotation as it is the gold standard of vitamin C serums. Why you ask? Firstly, the science and clinical testing behind the brand's products: In this serum's case, it's patented and clinically proven to reduce combined oxidative damage from free radicals generated by UV, ozone, and diesel exhaust by up to 41 percent. Additionally, the serum improves signs of photodamage, lines, and wrinkles while boosting radiance and even fading dark spots. Though this didn’t earn our highest score, we found it is indeed worth the hype. Not only did it make our skin glow, but it also smoothed fine lines and texture on our skin. It also pairs well with other products you may already have in your routine and doesn't leave a sticky residue. We do want to point out that our tester, who has used vitamin C daily in her morning routine for eight years, wasn’t expecting a notable difference. However, they were pleasantly surprised: “I ended up seeing a difference in the texture of my skin and fine lines during this six-week test. Everything is a bit smoother and softer — this is the only product/step that changed.” One other thing we noticed about this product is the odor. It has what might be described as a sour scent, akin to the smell of a hot dog. Size: 1 oz. | Star Ingredients: 15% pure vitamin C (L-ascorbic acid), 1% vitamin E, 0.5% ferulic acid | Skin Type: All, including sensitive People / Shannon Bauer Best Budget Yes To Grapefruit Brightening Serum Amazon View On Amazon $15 View On QVC $15 Pros It only took a few days to reap the benefits of this serum Formulated with over 95 percent natural ingredients Cons It has a strong fragrance, which may not be for everyone This Yes to Grapefruit serum boasts PHAs that gently exfoliate and vitamin C to boost radiance. In our testing, we saw results in just a few days. This serum was refreshing, not greasy or sticky, and it imparted a subtle glow upon application. It can be used morning or night, but we prefer to use it in the morning for the light grapefruit scent and instant skin-radiance boost. However, if you prefer non-scented serums, you should opt for another pick on our list. Size: 0.95 oz. | Star Ingredients: Vitamin C, 5% polyhydroxy acids | Skin Type: Dry People / Allison Vancura People / Allison Vancura People / Allison Vancura Best for Fighting Sun Damage Herbivore Brightening Serum Herbivore View On Sephora $65 Pros 15 percent vitamin C effectively brightens dark spots and antioxidant-rich turmeric evens out the skin tone Didn’t sting our sensitive-skinned testers on application Cons Light gingery scent from the added turmeric, but we found it to be pleasant By now, anyone who’s tapped into the skincare world (and many who aren’t) probably know about the damaging effects of sun exposure on the skin, which can cause dark spots, fine lines, and scarring. This Herbivore Vitamin C and Turmeric Brightening Serum aims to combat these common concerns with a high percentage of stable vitamin C. What makes this creamy serum stand apart from others we’ve tested is the inclusion of turmeric, an ingredient that’s packed with antioxidants. Even our testers with the most sensitive, rosacea-prone skin agreed that this serum did not string or tingle upon application. The product is formulated without any additional fragrance (another win for the sensitive skin community), but the turmeric does give it a slight gingery smell. It has a light, creamy texture and sinks into the skin like a thin moisturizer, leaving behind a subtle glow. Size: 1 oz. | Star Ingredients: 15% THD vitamin C, turmeric | Skin Type: All These Are the Best Face Sunscreens We Tested in 2024 Best for Mature Skin Klur Brilliant Light Repair Serum Klur View On Klur.co View On Credo Beauty $88 Pros Absorbs into the skin quickly and works well with other skincare products Our 63-year-old tester said she noticed her skin firm up over time while using this product Felt hydrating and smoothing upon application Cons It is on the expensive side, but a little bit goes a long way (and it has a high concentration of vitamin C, which does provide results). Formulated with a blend of 20 percent bioavailable vitamin C in tandem with a skin-strengthening and calming complex of plant extracts to help even skin tone sans unwanted irritation, this clean formula absorbs in seconds and, for some skin types, even helps control excess oil production. We found the Klur Vitamin C Serum to be super hydrating and smoothing upon application. Plus, our tester noted that her 63-year-old skin felt firmer over time. It's expensive, but a little bit goes a long way. Size: 1 oz. | Star Ingredients: 20% bioavailable vitamin C | Skin Type: All People / Nellah McGough People / Nellah McGough Best for All Skin Tones BeautyStat Universal C Skin Refiner Amazon View On Amazon $85 View On Nordstrom $73 View On Ulta $60 BeautyStat is a skincare company founded by cosmetic chemist Ron Robinson, and the brand’s hero product, the Universal C Skin Refiner, was the very first serum to include 20 percent stable vitamin C (meaning it won’t oxidize or change colors). The brightening formula was created to work on all skin types, textures, and tones. In BeautyStat’s clinical testing, 100 percent of participants agreed that their skin tone looked more even and their pores looked smaller. The formula includes a powerful 20 percent concentration of vitamin C, so sensitive-skinned folks should tread lightly at first, applying the serum twice a week in the mornings before moving on to more regular application. The texture is smooth and slightly mattifying, and it easily blends into the skin without leaving any sticky residue behind. Editors Say “I swear by the Universal C Skin Refiner for lightening acne scars and hyperpigmentation. I have sensitive, rosacea-prone skin, so I started by applying the formula about twice a week before increasing use to every other day. My skin has brightened so much since I started using it!” —Cai Cramer, PEOPLE shopping writer Size: 1 oz. | Star Ingredients: Vitamin C, squalane, green tea | Skin Type: All People / Samantha Stevenson Best for Immediate Glow Olay Vitamin C Peptide 24 Serum Target View On Target $30 View On Ulta $40 View On Walgreens $30 Pros Provided an immediate glowing effect, and our skin felt refreshed hours after application Visible hydration and radiance of our skin Cons Might not be for you if you don't enjoy citrus-based products Vitamin C percentage is not listed Olay is a skincare brand staple. If scent is a vital factor in your skin products, you'll love that this serum wakes up your senses and boosts radiance in the skin. Formulated with vitamin C, skin barrier protecting niacinamide, and hydrating peptides, the citrus-scented formula is clinically proven to help skin look visibly more hydrated in one day and more radiant after one month. We loved that this serum resulted in visible hydration and radiant-boosting effects and even after several hours, our skin remained feeling refreshed. It had an immediate glowing effect, but it faded within an hour, so if glowing skin isn't your top priority, but feeling refreshed and hydrated is, this is a great value pick. We absolutely love the scent but realize it may not be for everyone, especially those with fragrance sensitivities. Size: 1.3 oz. | Star Ingredients: Vitamin C, niacinamide, peptides | Skin Type: All People / Nicole Harris People / Nicole Harris Best for Dark Spots Goodal Vitamin C Dark Spot Serum+ Amazon View On Target $27 View On Yesstyle.com $31 Pros It has skin barrier-protecting and collagen-boosting ingredients like centella asiatica (tiger grass). Our skin saw improved skin tone and texture and reduced dark spots in just a few days. Cons The vitamin C percentage is not listed. Finding the right vitamin C to fade dark spots can take a lot of trial and error. (And we all know that can get expensive.) However, this dark spot serum is relatively budget-friendly and is packed with a powerful blend of fresh green tangerine extract (an ingredient that offers 10 times more vitamin C than lemons), niacinamide, and arbutin that helps improve dark spots and post-acne hyperpigmentation. It also has centella asiatica (tiger grass) to protect the skin barrier and boost collagen. After only a few days of using this product, we saw a reduction of dark spots. While the tangerine scent might not be for everyone, our skin felt healthier, more radiant, and clearer after just a few days, and we think this product is an absolute steal. Size: 1.01 oz. | Star Ingredients: Vitamin C, centella asiatica, niacinamide, arbutin | Skin Type: All, including sensitive Best for Sensitive Skin CeraVe Skin Renewing Vitamin C Serum Amazon View On Amazon $18 View On Target $24 View On Ulta $30 Pros Lightweight and easy to apply Reduction in post-breakout hyperpigmentation and fine lines, especially around the mouth Lower concentration of vitamin C, which makes it safer for sensitive skin Cons Packaging is great for keeping the product stable, but it is tricky to open Drugstore products may offer more budget-conscious prices, but that doesn’t mean they’re any less effective. For sensitive or breakout-prone skin, this dermatologist-developed, allergy-tested, non-comedogenic formula has all the necessities that lead to healthier, radiant skin, including 10 percent L-ascorbic acid, hyaluronic acid, skin barrier-protecting ceramides, and soothing vitamin B5. Our tester loved this lightweight, easy-to-apply product and said she will continue to use it at home until she uses the very last drop. She did note that the packaging can be tricky because while it's securely packaged for delivery, there are a few steps to opening the cap that took a second to figure out. While using, her acne-prone skin with post-breakout hyperpigmentation saw a reduction in the appearance of those spots while the formula felt light on the skin. She even noticed a reduction in fine lines around her mouth area. Size: 1 oz. | Star Ingredients: 10% pure vitamin C (L-ascorbic acid), ceramides, hyaluronic acid, vitamin B5 | Skin Type: All Best for Dry Skin Sephora Collection Super Glow Serum with Vitamin C+E Sephora View On Sephora $21 View On Kohls.com $21 Pros Noticeable, dewy results in just a few weeks Formulated with 97 percent ingredients that are naturally sourced Greatly improved the firmness and smoothness of the skin in just a few weeks Cons Not great for those with oily skin If natural ingredients are your jam, we have some good news. This fast-absorbing serum is made with 97 percent naturally sourced ingredients, including natural forms of vitamins C and E alongside peptides derived from marine algae that firm and hydrate to combat and smooth wrinkles. In testing, we saw dewier and healthier skin in just a few weeks. Of all the serums we tested, this one definitely had a "wow" factor, and our tester felt that her skin looked younger after using this product for a few months. However, if you have oily skin, this might not be the best serum for you, and it's packaged in a glass bottle, which made our tester a little nervous that she might shatter it at any moment. But from our standpoint, this product, which provided a vast skin improvement from a non-plastic bottle is a fantastic deal. Size: 1.01 oz. | Star Ingredients: Vitamin C, vitamin E, natural peptides from marine algae | Skin Type: Dry, balanced People / Cynthia Sanz People / Cynthia Sanz Best for Combination Skin TruSkin Vitamin C Facial Serum Amazon View On Amazon $22 View On Target $24 View On Walmart $22 Pros Fully absorbed in just 30 seconds, making it easy to implement into a skincare routine Hydrating enough to use on combination skin as the sole moisturizer Our skin remained glowing up to 12 hours later Cons The vitamin C percentage is not listed In testing, we found that this serum was absorbed in just 30 seconds and was hydrating enough to use on combination skin without the need for any additional moisturizer. One of our testers said she started receiving compliments on her skin's complexion and credits that to this product. "I'm way more confident in stepping outside without any makeup. I took a selfie after flying on a 13-hour flight and my bare skin still looked bright and glowy," she adds. The vitamin C percentage is not listed, so those who are new to vitamin C or anyone with sensitive skin should test a small amount of the product on your skin first before applying it to your face. Size: 1 oz. | Star Ingredients: Vitamin C, vitamin E, and hyaluronic acid | Skin Type: All People / Emily Cieslak Best for Clogged Pores InnBeauty Project Vitamin C + Green Superfoods Jelly Serum Sephora View On Sephora $38 View On Kohls.com $32 View On Innbeautyproject.com Pros Helped dissipate acne flare-ups Feels like a lush smoothie for your face Formula's oils are non-comedogenic, meaning they won't clog pores Cons The vitamin C percentage is not listed If you're an oil lover or somewhere in between, a serum-oil hybrid feels like an ideal match. This serum is like a lush smoothie for your face that won't clog pores — though our tester shared the formula didn't completely stop acne from occurring. However, the serum did help acne flare-ups dissipate more quickly after our tester added this product to their acne-prone routine. If you try to avoid oil-based products, though, this one might not be for you. Size: 1 oz. | Star Ingredients: Vitamin C (tetrahexyldecyl ascorbate), 15 super-greens complex, and pomegranate stem cells | Skin Type: All Best Smoothing Drunk Elephant C-Firma Fresh Vitamin C Day Serum Amazon View On Sephora $79 View On Ulta $79 Pros Gave us softer, plumper skin and reduced breakouts It's proven to maintain nearly 95 percent of active vitamin C for one year after the product was mixed Our skin was noticeably more glowy and smooth after one month of regular use Cons Because it has a strong vitamin C concentration, it might not be an ideal starter serum for anyone new to vitamin C This OG serum is still holding up to its hype. The brand's proprietary C-Firma is designed to be mixed by you before its first use. This helps maximize potency; each bottle is proven to maintain almost 95 percent efficacy up to one year after mixing. As for real-world results, we found that our skin was softer, plumper, and more glowy after six weeks, and our monthly chin breakouts were significantly reduced. One of our testers even started receiving compliments on her skin and said after three to four weeks of use, she'd catch herself in the mirror and think, "Wow, my skin looks so bright and smooth!" That self-confidence boost helps justify the price tag. However, this Drunk Elephant serum has a 15 percent vitamin C concentration, so if you're just starting out with a vitamin C step in your skincare routine, it's better to start with a 10 percent concentration. Also, one of our testers noted an odd smell upon application but said it quickly faded. Size: 1 oz. | Star Ingredients: Vitamin C (15% L-ascorbic acid), ferulic acid, vitamin E | Skin Type: All People / Julia Sayers Gokhale People / Julia Sayers Gokhale People / Julia Sayers Gokhale Best for Dull Skin Biossance Squalane + Vitamin C Rose Oil Sephora View On Sephora $74 View On Biossance.com View On Kohls.com $40 Pros Absorbed quickly and didn't leave behind a greasy residue It's a great serum for a variety of skin types The plumping effect of this product gave our skin an overall refreshed look Cons It's expensive, but a little goes a long way, so we think it's worth it Vitamin C percentage is not listed Applying face oil might feel like it goes against everything you learned about skincare. However, squalane soaks right into the skin and is usually well tolerated by most skin types, including oily and combination skin. In testing, we found that even testers with naturally oily skin loved this product, saying that the oil absorbed surprisingly well and never felt greasy post-application. The glow of this serum is excellent at combating dull skin, and one of our testers said she'd received so many compliments on her skin since incorporating this product into her daily routine. It also made her skin extra plump, as if she'd just gotten a great night's sleep. This product is on the pricier side, but a little goes a long way, so we think it's worth it. Size: 1.01 oz. | Star Ingredients: Damascus rose oil, vitamin C, and Chios crystal oil | Skin Type: All People / Madison Yauger Best Exfoliating Ole Henriksen Banana Bright Vitamin C Serum Sephora View On Sephora $68 View On Ulta $68 View On Olehenriksen.com Pros Hyaluronic acid is included in the formula, so you can save time by cutting that step in your skincare routine Offers gentle exfoliation while improving skin elasticity and evening skin tone Cons While some may want a higher concentration of vitamin C, it may irritate those with sensitive skin With this 15 percent vitamin C-infused serum, you won't need to layer hyaluronic acid because it's already in this formula, which is a plus if you're an impatient skincare applicator. This serum has such a hydrating effect that our tester made it through a full day of Zoom calls and still looked dewy. It made our skin glowy, hydrated, and refreshed, and we loved the slight scent. It has a 15 percent vitamin C concentration, so if you're new to vitamin C or have sensitive skin, you may want to opt for a product with a 10 percent concentration. Size: 1 oz. | Star Ingredients: 15% vitamin C (ethyl ascorbic acid), PHAs, and hyaluronic acid | Skin Type: All People / Ivy Ford What to Know About Vitamin C Serum Yes, you can use it with retinol products. If your skin is not sensitive, you can apply both vitamin C and retinol at night. "If I'm going to use either retinol or vitamin C, I'll take retinol," Chung shares. This pairing can be a dynamic duo that gets you a little more bang for your buck if your skin isn't prone to irritation. "Retinol is your gold standard for increasing collagen and improving the turnover of skin cells while Vitamin C acts as a supporting cast," she explains. Prone to irritation? No problem. Instead, stick with vitamin C for the daytime and a retinol formula at night. Opt for a low concentration if you have sensitive skin. Most everyone can benefit from layering vitamin C into their routine, whether it be vitamin C serum or in an eye cream for dark circles. But if your skin is reactive or sensitive, Chung says to avoid high-concentration formulas that may cause irritation. Some vitamin C products are formulated specifically for sensitive skin, like SkinCeuticals C E Ferulic. If you have dry skin, try Sephora Collection’s Ultra Glow Serum, our top pick for dry skin. Look for dark or opaque packaging. Vitamin C serum that is packaged in a dark glass bottle or opaque plastic tube will last longer than one stored in clear packaging. It’s also important to store your vitamin C serum in a cool, dark place to avoid UV exposure, which can make it less effective. The Klur Brilliant Light Multi-Correctional Repair Serum, which is in a dark glass bottle, and our best overall, L'Oreal Paris Revitalift Vitamin C Serum, in an opaque tube, are examples of the ideal packaging for vitamin C serums. Consider the other ingredients. Vitamin C is usually thoughtfully formulated with complementary ingredients. The reason for this? "Vitamin C products often need oiler vehicles to maintain stability," Chung tells PEOPLE. However, she notes this can be problematic for some skin types (like acne-prone skin). So if you are prone to acne, seek formulas with squalane and rosehip oils, as they are non-comedogenic. Vitamin C can also be quite effective in hyaluronic acid serums. As far as the actual vitamin C goes, Chung recommends products that use L-ascorbic acid as its active ingredient, preferably with vitamin E, for the best stability. This is because L-ascorbic acid is the most potent and effective form of vitamin C. Our best daytime serum, Drunk Elephant C-Firma Fresh Vitamin C Day Serum, contains both L-ascorbic acid and vitamin E. Our tester applying Yes to Grapefruit Daily Brightening Serum. People / Allison Vancura Behind the Scenes To find the best vitamin C serums on the market, we gathered top-rated products and our team used them over a period of six weeks. We tested 32 vitamin C serums altogether on a variety of different skin types. All in all, we selected 15 vitamin C serums we feel confident would work well for a variety of people. Ease of Use: One of the biggest factors we considered was how easy it was to apply and layer the products with the rest of our normal skincare routines. We noted how well each dropper distributed the serum and if the bottle felt high-quality or breakable.Absorption: The next step was distribution, where we analyzed whether or not the serum absorbed quickly (in under 15 seconds) or took more than a minute to sink in, which would earn a poorer rating.Skin Texture: A major change we looked for when using these products was an improvement in our skin texture. We took photos to document our progress and noted any changes, no matter how big or small, in the smoothness and softness of our skin after the six week testing period had passed.Glow: Vitamin C is supposed to brighten your skin, so we watched closely to see if our complexions boasted an extra glow after a few weeks of proper testing. We kept tabs on any extra dewiness and luminosity that appeared (or didn't) and rated each accordingly (more glow equals a higher rating).Firming: Another factor we took into consideration was the tightness of our skin after the testing period ended. Extra points if we noticed a reduced appearance of wrinkles as a result of these products.Overall Look: In general, we judged the overall look of our skin based on the luminosity of our complexions, the tautness of our skin, and if our dark spots and/or acne had faded since our first time using the serums.Value: The final step was analyzing the retail price, which was only revealed to us once the test was complete. After learning the amounts, we asked ourselves if we thought the price was worth it (or better yet, if we would have paid even more for the amazing results it delivered) and rated the quality based on our answers. Frequently Asked Questions How should I use vitamin C serum? There is one must when using vitamin C (and caring for your skin in general): SPF. "I recommend using vitamin C every morning before sunscreen," Los Angeles-based celebrity esthetician Shani Darden tells PEOPLE. "The combo of vitamin C serum and sunscreen is perfect for daytime protection." How often should I use vitamin C? Darden says a slow start is best if you're starting a vitamin C serum for the first time or adding a new vitamin C serum you haven't used before. Begin by using a small amount once a day, three or four days a week, and work your way up to a daily application."Vitamin C is a very active ingredient and it can cause irritation," she explains. "Introducing it slowly will allow time for your skin to acclimate to the product without causing any irritation. Additionally, adding the product in slowly and by itself will make it easier to pinpoint how well it works for your skin." When should I apply vitamin C serum? The best time to apply vitamin C serum depends on what other beauty products you’re using as well as your skin sensitivity level. Learning how to layer products and when to use them is a science, but once you get your routine down, it’s super simple. Chung encourages her patients with sensitive skin to use vitamin C serum in the morning, but you can also apply it at night with retinol. If your skin isn’t prone to sensitivity, the combination of vitamin C and retinol may give you faster results. If you are susceptible to irritation, use a vitamin C serum in the morning and a retinol at night. Why Trust PEOPLE? Bianca Lambert is a freelance writer for PEOPLE and is also a contributing writer for Byrdie, specializing in natural hair and skincare. She has worked as a freelance beauty writer for over four years and has an extensive knowledge of beauty ingredients and how they affect your skin, hair, and face. For this article, she consulted our testing results and interviewed board-certified dermatologists and celebrity estheticians to provide real-world experience and expert guidance on the topic at hand. This article was most recently updated by PEOPLE shopping writer Cai Cramer, with updated insights and fresh picks. Meet Our Experts • Dr. Christina Lee Chung is a board-certified dermatologist at Schweiger Dermatology Group in Pennsylvania. • Shani Darden is a Los Angeles-based celebrity esthetician and founder of Shani Darden Skin Care. What Is People Tested? We created the PEOPLE Tested seal of approval to help you find the very best products for your life. We use our unique methodology to test products in three labs across the country and with our network of home testers to determine their effectiveness, durability, ease of use, and so much more. Based on the results, we rate and recommend products so you can find the right one for your needs. But we don’t stop there: We also regularly re-review the categories in which we’ve awarded the PEOPLE Tested seal of approval — because the best product of today might not be the best of tomorrow. And by the way, companies can never buy our recommendation: Their products must earn it, fair and square. In short, PEOPLE Tested provides recommendations you can trust — every day, every purchase.