# COSRX The Vitamin C 13 Serum

Vitamin C 13% Serum, 20 ml, with Niacinamide.

- Brand: COSRX
- Product: The Vitamin C 13 Serum
- Price: $20.99
- Availability: Out of stock
- Size: 20ml
- Market: Korean market, the version sold in Korea
- Made in: Republic of Korea
- EAN (barcode): 8800311121911
- Category: Serums & Ampoules

## Key benefits

- Ascorbic acid is declared at 13%, matching the name.
- Ethyl Ascorbic Acid is another, more stable vitamin C form 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.

## 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.

## How to use

1. Use the Vitamin C 13 Serum in the morning, after toner and before moisturizer, on skin that has dried off rather than damp skin.
2. Three or four drops covers the whole face and neck. Press it in and let it settle for a minute.
3. Toner first, this second, then moisturizer, then sunscreen as the last step of the morning.
4. 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.

## Ingredients

Water, Ascorbic Acid (13%), Butylene Glycol, Dipropylene Glycol, Tromethamine, 3-O-Ethyl Ascorbic Acid, Panthenol, Acetyl Glucosamine, Caffeine, Sodium Hyaluronate, Sodium Sulfite, Disodium EDTA, Glutathione, Adenosine, Gardenia Florida Fruit Extract, Allantoin, Dextrin, Squalane, Tocotrienols, Tocopherol, Elaeis Guineensis (Palm) Oil, Arginine, Niacinamide, Pentylene Glycol, Glycyrrhiza Glabra (Licorice) Root Extract

## FAQ

### What makes this a 13% vitamin C serum rather than a lower-strength brightening product?

Ascorbic acid appears second on the ingredient list, directly after water, declared at 13%, which is the number in the product name. A second, more stable vitamin C form, 3-O-ethyl ascorbic acid, follows a few entries later, and caffeine and sodium hyaluronate sit in the upper half of the list as well. That combination places this in the direct-acid category of vitamin C serums rather than a milder derivative-only formula.

### Will a 20 ml bottle of 13% vitamin C be too intense for my skin?

Direct ascorbic acid at this strength can sting or feel warm on skin that has not used it before, so easing in with alternate nights rather than daily use from the start is sensible. The list carries no fragrance, essential oil, denatured alcohol, silicone, paraben, or added colourant, removing several common irritant categories. Panthenol and allantoin sit mid-list as calming ingredients, though anyone with compromised or actively reactive skin should patch test before applying it broadly.

### Does this serum need weeks of use before tone improves?

Ascorbic acid, glutathione, and tocopherol work together as an antioxidant routine that builds over repeated daily applications rather than producing a change overnight. Niacinamide, positioned near the end of the list, adds a further ingredient associated with a more even-looking complexion over time. Applying it every morning for several weeks is the realistic window for judging whether tone and texture have shifted.

### Should this go on before or after my other morning serums?

This vitamin C serum is generally applied early in a morning routine, after toner and before heavier creams or sunscreen, since ascorbic acid performs its antioxidant role best close to the skin. Nothing on this ingredient list is known to conflict with a mineral or chemical sunscreen used afterward. Avoid layering it in the same session as a separate strong exfoliating acid, since stacking two direct acids at once raises the chance of irritation.

### How do I check that this 20 ml bottle is the real Korean-market formula?

This product's own barcode, 8800311121911, is a genuine EAN specific to this bottle, so matching that number against your box is a useful first check. COSRX also runs its own verification: the batch number and expiration date on your unit are entered on the checking page at cosrx.com, read directly off the packaging rather than from any listing. Using both the barcode and the batch check together is the most reliable way to confirm what you have is authentic.

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Page: https://korean-pharmacy.com/products/cosrx-the-vitamin-c-13-serum