COSRX
The Vitamin C 13 Serum (Single)
The everyday vitamin C serum in COSRX's line, for a brighter, more even look, worn after toner and before sunscreen.
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- Suited to
- SensitiveCompromised barrierUneven toneDull
- Helps with
- Barrier weaknessEarly environmental damageUneven tone and dullnessExcess oil
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- 30-day returns
- Free US shipping on orders of $100 or more
- Dispatched within 2 business days
How it works
This is the vitamin C step that goes into a morning routine and stays there. It belongs after toner and before moisturizer and sunscreen, on skin that is dry rather than wet. What changes is tone rather than texture: a brighter, more even look that shows after a few weeks of consistent mornings. Sunscreen over the top is the other half of the habit, and a morning routine that includes this step should not skip it. It suits someone who wants one active step in the morning and keeps the evening free for an exfoliant or a retinoid.
Key benefits
- Ascorbic acid is declared at 13%, matching the name.
- Another, more stable vitamin C derivative sits just below it on the list.
- Caffeine and sodium hyaluronate sit in the top ten of the list.
- Niacinamide, glutathione and licorice root extract round out the formula.
Key actives
Ascorbic Acid
declared at 13%, the direct vitamin C form in the name
Niacinamide
supports a clearer, more even look
Caffeine
an antioxidant that also brightens the look of the eye area
COSRX The Vitamin C 13 Serum (Single)
Is this single bottle the same formula as COSRX's other Vitamin C 13 packs?
The ingredient list here matches the direct-acid vitamin C formula COSRX sells across its Vitamin C 13 line: ascorbic acid declared at 13%, second after water, with 3-O-ethyl ascorbic acid as a second, more stable form a few entries later. Caffeine and sodium hyaluronate sit in the upper half of the list as well. Whether it is sold as a single bottle or a multipack, the same 13% ascorbic acid formula is what is inside.
Can I use this if I have sensitive skin that reacts to strong actives?
A direct ascorbic acid serum at this declared strength can feel warm or tingly on skin unused to vitamin C, so introducing it a few nights a week before daily use is a sensible approach. No fragrance, essential oil, denatured alcohol, silicone, paraben, or added colourant appear on the list, which removes several common irritants. Panthenol and allantoin offer some calming support mid-list, but patch testing first is still worthwhile for reactive skin.
When should I expect to see brighter, more even skin from daily use?
Ascorbic acid, glutathione, and tocopherol form an antioxidant combination that works with sustained daily use rather than a single application. Niacinamide, positioned toward the end of the list, adds a further ingredient linked to a more even-looking complexion over time. Give it consistent morning use for several weeks before judging whether your skin's tone and texture have shifted.
What should come immediately after this serum in a morning routine?
This vitamin C serum is typically applied early, after toner and before a moisturizer or sunscreen step, since ascorbic acid performs best close to clean skin. Nothing on the ingredient list is known to conflict with a standard sunscreen applied over it. It is generally not layered in the same session as a separate strong exfoliating acid, so keeping those two treatments on different days or times of day is the more cautious approach.
How do I make sure this single bottle is the genuine Korean-market formula and not a repackaged substitute?
The barcode on this bottle, 8809598455238, is a genuine EAN specific to this product, so matching it against your packaging is a straightforward first check. COSRX also verifies units through its own system: enter the batch number and expiration date printed on your unit at the checking page on cosrx.com, reading the codes straight off the box. Using both checks together, rather than relying on a seller's claim, is the reliable way to confirm what you have.
- Ships from
- California
Duties are prepaid. Nothing is owed at delivery. Returns are accepted for 30 days, by mail.
Orders ship from our California warehouse, dispatched within 2 business days, and arrive in 3 to 5 days. Shipping is free on orders of $100 or more.
We split shipments free, so one out-of-stock item never holds up the rest of your order.
Where this unit came from
- 1Seoul
Bought as Korean-market stock - 2Customs
Duty paid by us before it enters the US - 3California
Ships domestically, no international leg
We stock the version of a formula that is sold in Korea, not the release a brand prepares for another market under the same name.
Every unit keeps its original barcode and batch code intact, so the unit in your hands can be checked against the brand’s own records.
Import duties are paid by us before the parcel reaches you, so nothing is owed at the door, and returns run for 30 days.
Every claim on this page traces to the unit in the box, the barcode, the batch code and the price you can read for yourself.
Payment and security
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How to use
- Use the Vitamin C 13 Serum in the morning, after toner and before moisturizer, on skin that has dried off rather than damp skin.
- Three or four drops covers the whole face and neck. Press it in and let it settle for a minute.
- Toner first, this second, then moisturizer, then sunscreen as the last step of the morning.
- Once a day, in the morning. Do not stack it in the same routine as an exfoliating acid or a retinoid; give those the evening instead.
Reviews
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COSRX, Korean-market original
Vitamin C 13% Serum, with Niacinamide.
Verify your unit when it arrives
Verify your unit when it arrives
Korean-market stock with the original barcode and batch code intact, exactly as it left Korea.
COSRX verifies units itself. Find the verification page on cosrx.com and enter the batch number and expiration date printed on your unit. Read them off the package rather than from us, which is the point.
Source: COSRX FAQ
On the unit itself
- The Korean-market barcode, unaltered from the retail package.
- The manufacturer’s batch code, exactly as the maker printed it.
정품Genuine article, Korean-market stock
What professionals say
What professionals say
What skin-care professionals say about the key actives in this formula, quoted from the medical sources linked beside each.
Using topical vitamin C can result in less cell damage and better-looking skin.
Melissa Piliang, MDDermatologist, Cleveland Clinic It has also been proven that caffeine stimulates lipolysis, which Lupo et al postulated may contribute to improvements in lower eyelid sagging and puffiness.
Stacey J. PilkingtonDO, Azeal Dermatology Institute, The Journal of Clinical and Aesthetic Dermatology
1 more professional perspective
Niacinamide helps reduce the appearance of pores in a few ways. By strengthening the skin barrier and improving elasticity, pores appear less noticeable and more even.
Ashlyn YankeAesthetician, Cleveland Clinic
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