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The Vitamin C 13 Serum

The Vitamin C 13 Serum

Product Description

Product overview

Made in South Korea K-BEAUTY

A gentle, water-based vitamin C serum with 13% pure ascorbic acid that brightens skin, fades dark spots, and improves overall complexion. Formulated with Super Vitamin E (Tocotrienol) and Hyaluronic Acid for enhanced antioxidant protection and hydration. Perfect for vitamin C beginners and sensitive skin types seeking daily brightening without irritation.

13% Pure Vitamin C Clinically Tested Fragrance-Free Paraben-Free Silicone-Free Cruelty-Free Sensitive Skin Friendly Dermatologist Tested
Pregnancy
Yes
Fungal Acne
Caution
Comedogenic
1/5
Size
20ml / 0.67 fl.oz
Type
Water-Based Serum
Concerns
Dark Spots, Dullness
pH Level
~3.0 - 3.5
Storage
Refrigerate
Real reviews · YouTube Shorts
Why it's different

Brightening Power

13% pure ascorbic acid targets hyperpigmentation, dark spots, and uneven skin tone for a radiant complexion.

01

Texture & feel

SENSORY
Consistency
Lightweight, Watery
Scent
Light Citrus/Coppery
Absorption
Fast (30 seconds)
Finish
Non-Sticky, Dewy

Brightening Power

13% pure ascorbic acid targets hyperpigmentation, dark spots, and uneven skin tone for a radiant complexion.

Super Antioxidant Protection

Tocotrienol (Super Vitamin E) provides up to 50x more antioxidant power than regular Vitamin E to fight free radical damage.

Deep Hydration

Hyaluronic Acid and Allantoin deliver moisture deep into skin layers while soothing and preventing irritation.

Multi-Vitamin Complex

Contains Niacinamide, Panthenol, and Glutathione for enhanced brightening, barrier support, and anti-aging benefits.

02

Safety & compatibility

SAFE
Pregnancy & Breastfeeding Safe

Vitamin C (ascorbic acid) is considered safe during pregnancy and breastfeeding. No retinoids, hydroquinone, or high-concentration salicylic acid present.

Fungal Acne - Use with Caution

Contains Squalane and Elaeis Guineensis (Palm) Oil which may feed malassezia in some individuals. Patch test recommended if prone to fungal acne.

Low Comedogenic Risk

Rating 1/5. Lightweight, water-based formula with minimal pore-clogging ingredients. Suitable for most acne-prone skin types.

Sensitive Skin Approved

Clinically tested as non-irritating on 30 subjects over 24 hours. Fragrance-free and formulated for daily use on sensitive skin.

03

Ingredient breakdown

INGREDIENTS

Ascorbic Acid (Pure Vitamin C) 13%Proven

The gold-standard form of Vitamin C, L-ascorbic acid directly penetrates skin to inhibit melanin production, boost collagen synthesis, and neutralize free radicals for brighter, firmer skin.

  • Brightening: Inhibits tyrosinase enzyme to reduce melanin production and fade existing dark spots
  • Anti-Aging: Stimulates collagen synthesis and protects existing collagen from degradation
  • Antioxidant: Neutralizes UV-induced free radicals to prevent photoaging
Pure ascorbic acid is unstable and prone to oxidation. Store in refrigerator and use within 6 months of opening.

3-O-Ethyl Ascorbic Acid SupportingProven

A stable, water-soluble derivative of Vitamin C that converts to pure ascorbic acid in the skin. Provides extended brightening benefits without the irritation potential of L-ascorbic acid.

  • Stability: Resists oxidation better than pure ascorbic acid for longer shelf life
  • Penetration: Slowly releases Vitamin C deep into skin layers for prolonged effects
  • Gentle: Less irritating than pure Vitamin C, suitable for sensitive skin
The dual Vitamin C approach (pure + derivative) provides both immediate and sustained brightening action.

Tocotrienol (Super Vitamin E) SupportingProven

A superior form of Vitamin E with up to 50 times greater antioxidant efficacy than regular tocopherol. Enhances Vitamin C stability and provides powerful anti-aging benefits.

  • Synergy: Stabilizes and regenerates Vitamin C, enhancing its effectiveness
  • Anti-Aging: Prevents oxidative damage to cell membranes and reduces wrinkle formation
  • Protection: Shields skin from UV damage and environmental stressors

Sodium Hyaluronate SupportingProven

Low molecular weight hyaluronic acid that penetrates deep into skin to attract and retain moisture, plumping skin and reducing the appearance of fine lines.

  • Hydration: Holds up to 1000x its weight in water for intense moisture retention
  • Plumping: Reduces appearance of fine lines by hydrating from within
  • Barrier Support: Strengthens skin's moisture barrier function

Niacinamide (Vitamin B3) SupportingProven

A multi-functional powerhouse that brightens skin, minimizes pores, strengthens the skin barrier, and works synergistically with Vitamin C for enhanced results.

  • Brightening: Inhibits melanin transfer to reduce hyperpigmentation
  • Pore Refining: Regulates sebum production and minimizes enlarged pores
  • Barrier Repair: Increases ceramide synthesis for stronger, healthier skin

Glutathione SupportingPromising

The body's master antioxidant that supports skin brightening and provides cellular protection against oxidative stress.

  • Brightening: Inhibits melanin production for a more even skin tone
  • Antioxidant: Regenerates other antioxidants including Vitamins C and E
  • Detoxification: Helps neutralize harmful compounds and protect cells

25 ingredients

Water, Ascorbic Acid(13%), Butylene Glycol, Dipropylene Glycol, Tromethamine, 3-0-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

FREE FROM: Parabens, Artificial Fragrances, Artificial Dyes, Alcohol (Ethanol), Mineral Oils, Essential Oils, Silicones, Sulfates
04

Where it fits in your routine

ROUTINE
1
Cleanser
2
Toner
3
Vitamin C Serum
4
Essence/Serum
5
Moisturizer
6
Sunscreen (AM)

Apply after toner on clean skin. Wait 1-2 minutes before layering other products. Always follow with SPF 30+ sunscreen in the morning.

05

How to use

HOW TO USE
1

Shake Gently

Shake the bottle 1-2 times from side to side before each use to ensure ingredients are well-mixed.

2

Dispense 2-3 Drops

After cleansing and toning, apply 2-3 drops onto fingertips. A little goes a long way with this concentrated formula.

3

Gently Massage

Starting from the center of your face, gently pat and massage the serum outward toward the edges. Avoid direct eye contact.

4

Wait & Layer

Allow 1-2 minutes for absorption before applying next skincare steps. Follow with moisturizer and SPF 30+ sunscreen in the morning.

06

Who is it for?

WHO

Perfect for you if:

  • You're new to Vitamin C serums and want a gentle introduction
  • You have hyperpigmentation, dark spots, or uneven skin tone
  • Your skin looks dull and lacks radiance
  • You want anti-aging benefits without harsh irritation
  • You have sensitive skin that reacts to stronger actives
  • You're looking for an affordable, effective K-beauty brightening serum
  • You want to prevent early signs of aging

Consider alternatives if:

  • You're experienced with Vitamin C and need higher concentrations (try COSRX 23%)
  • You have severe hyperpigmentation requiring prescription-strength treatments
  • You cannot store products in the refrigerator
  • You're prone to fungal acne (malassezia folliculitis)
  • You prefer oil-based or anhydrous Vitamin C formulations
  • You want a larger bottle size for longer-term use
07

Skin type compatibility

SKIN TYPES
Oily Skin
Excellent

Lightweight, water-based formula absorbs quickly without adding shine or greasiness. Helps brighten post-acne marks.

Dry Skin
Good

Contains Hyaluronic Acid for hydration, but dry skin types may need a richer moisturizer on top for optimal comfort.

Combination Skin
Excellent

Balances well across different face zones. Light enough for oily T-zone while still providing hydration for dry areas.

Sensitive Skin
Excellent

Clinically tested as non-irritating. 13% concentration is gentle yet effective. Fragrance-free formula minimizes reaction risk.

Acne-Prone Skin
Good

Low comedogenic rating (1/5). Great for fading post-inflammatory hyperpigmentation. Contains Niacinamide for pore care.

Mature Skin
Excellent

Boosts collagen production, improves elasticity, and reduces fine lines. Adenosine provides additional anti-wrinkle benefits.

08

Results timeline

WEEK 8-12
Week 1-2

Immediate Radiance

Skin appears brighter and more hydrated. The lightweight formula absorbs quickly, leaving a subtle glow. Some users may experience mild tingling initially as skin adjusts.

85% noticed improved radiance
Week 3-4

Visible Brightening

Noticeable improvement in overall skin tone. Dark spots begin to fade. Clinical trials show 3.94% improvement in brightness after 4 weeks of use.

78% saw brighter skin tone
Week 5-8

Dark Spot Fading

Significant reduction in hyperpigmentation and post-acne marks. Skin texture becomes smoother. Clinical results show 31.92% improvement in redness.

72% noticed faded dark spots
Week 8-12

Anti-Aging Benefits

Improved elasticity and reduced fine lines become visible. Clinical trials demonstrate 10.64% improvement in wrinkles around the eye area and 36.97% reduction in pore volume.

65% reported firmer skin
09

Ratings by platform

10K+ REVIEWS
Amazon
4.6
Rating
5,800+
Reviews
Main complaint: Small bottle size (20ml) runs out quickly for daily users
iHerb
4.5
Rating
2,400+
Reviews
Main complaint: Natural vitamin C scent may be off-putting for some users
YesStyle
4.4
Rating
1,200+
Reviews
Main complaint: Must be stored in refrigerator to prevent oxidation
COSRX Official
4.7
Rating
850+
Reviews
Main complaint: Watery consistency can be tricky to dispense without dripping
10

Pros & cons

BALANCED

Praised

  • Effective brightening results for dark spots and hyperpigmentation
  • Gentle formula suitable for sensitive skin and vitamin C beginners
  • Lightweight, fast-absorbing texture without stickiness
  • Affordable compared to high-end vitamin C serums
  • Contains multiple beneficial ingredients (Vitamin E, HA, Niacinamide)
  • Fragrance-free and clinically tested for irritation
  • Visible results in 2-4 weeks of consistent use

Criticized

  • Small bottle size (20ml) depletes quickly with daily use
  • Requires refrigeration to prevent oxidation
  • Short shelf life once opened (6 months)
  • Natural coppery/metallic vitamin C scent
  • May not be potent enough for experienced vitamin C users
  • Dropper can be messy with watery formula
  • Not fungal acne safe due to certain oils
11

Budget-friendly alternatives (dupes)

DUPES
85% Match
Vitamin C Suspension 23% + HA Spheres 2%
$6.80
Budget Pick

Higher concentration (23%) in silicone-based suspension. Gritty texture and longer absorption time. More affordable but may be too strong for sensitive skin.

70% Match
Freshly Juiced Vitamin Drop
$23.00
Similar Price

Lower concentration (5%) makes it gentler but slower-acting. Better for very sensitive skin. Larger bottle (35ml) lasts longer. More stable formula.

65% Match
20% Vitamin C + E Ferulic Acid Serum
$24.95
Similar Price

Higher concentration with stabilizing ferulic acid. Larger bottle (30ml). More potent but may cause more irritation for sensitive skin types.

50% Match
The Vitamin C 23 Serum
$25.00

Same formula but with 23% vitamin C concentration. Better for experienced users who need stronger results. Not recommended for vitamin C beginners.

12

Comparison with competitors

SIDE-BY-SIDE

SkinCeuticals C E Ferulic

Vitamin C Type L-Ascorbic Acid 15%
Size 30ml
Additional Actives Vitamin E, Ferulic Acid
Texture Silky, Lightweight
Best For Luxury Seekers, All Skin Types
Freshly Juiced Vitamin Drop
Vitamin C Type Ascorbic Acid 5%
Size 35ml
Additional Actives Centella, Yuja Extract
Texture Slightly Oily, Warming
Best For Very Sensitive Skin, Beginners
Vitamin C Suspension 23% + HA Spheres 2%
Vitamin C Type L-Ascorbic Acid 23%
Size 30ml
Additional Actives HA Spheres
Texture Gritty, Silicone-Based
Best For Budget-Conscious, Experienced Users
13

Storage & shelf life

6 MONTHS
Period After Opening (PAO)

6 months after opening. Pure vitamin C oxidizes quickly once exposed to air. Use consistently for best results.

Storage

Store upright in refrigerator (3-10°C / 37-50°F) to prevent oxidation. Keep away from direct sunlight and heat sources.

Packaging

Dark glass dropper bottle with specially designed cap to control gas buildup from vitamin C oxidation process.

Travel Friendly

Yes, under 100ml TSA limit. For travel, keep in insulated bag with ice pack to maintain cool temperature.

13

Frequently asked questions

FAQ

Yes, this serum is generally considered safe during pregnancy and breastfeeding. Vitamin C (ascorbic acid) is a pregnancy-safe ingredient. The formula contains no retinoids, hydroquinone, or high-concentration salicylic acid. However, as with any skincare product, consult your healthcare provider before use during pregnancy or nursing.

Use with caution. The serum contains Squalane and Elaeis Guineensis (Palm) Oil, which may feed malassezia yeast in some individuals prone to fungal acne. If you have a history of fungal acne, perform a patch test first or consider a fungal acne-safe alternative vitamin C serum.

It's best to avoid using vitamin C with retinol, AHA, or BHA in the same routine to prevent irritation. Use vitamin C in the morning and retinol at night. If using acids, alternate days or apply vitamin C in AM and acids in PM. The formula already contains niacinamide, which works synergistically with vitamin C.

This serum is excellent for all skin types, especially sensitive skin and vitamin C beginners. The 13% concentration is effective yet gentle. It's ideal for oily, combination, normal, and sensitive skin. Dry skin types may need additional moisturizer. Those with very experienced skin may prefer the 23% version for stronger results.

Most users notice improved radiance within 1-2 weeks. Visible brightening and dark spot fading typically occurs around weeks 3-4. Clinical trials showed 31.92% improvement in redness and nearly 37% reduction in pore volume after consistent use. Full anti-aging benefits like improved elasticity become apparent after 8-12 weeks of daily use.

Apply after cleansing and toning, before other serums and moisturizer. The order is: Cleanser → Toner → Vitamin C Serum → Essence/Other Serums → Moisturizer → Sunscreen (AM). Apply 2-3 drops and wait 1-2 minutes before layering other products. Always follow with SPF 30+ sunscreen in the morning.

No, this serum has a low comedogenic rating of 1/5. The lightweight, water-based formula contains minimal pore-clogging ingredients. It also includes Niacinamide which helps minimize pores and regulate sebum production. It's suitable for most acne-prone skin types, though those with fungal acne should exercise caution.

The serum has a 6-month PAO (Period After Opening) when stored properly in the refrigerator. Pure vitamin C oxidizes when exposed to air, light, and heat. Signs of oxidation include color change from pale yellow to dark orange/brown and a metallic smell. Once oxidized, the serum loses effectiveness and should be discarded.

— Skincarisma verdict
4.5 / 5 ★★★★★

Verdict: COSRX The Vitamin C 13 Serum is an excellent entry-level vitamin C serum that delivers real brightening results without the irritation commonly associated with pure ascorbic acid. The 13% concentration hits a sweet spot between efficacy and gentleness, making it perfect for vitamin C beginners and sensitive skin types. The addition of Tocotrienol (Super Vitamin E), Hyaluronic Acid, Niacinamide, and Glutathione elevates this beyond a simple vitamin C serum into a multi-functional brightening treatment. While the small bottle size and refrigeration requirement may be drawbacks for some, the affordable price point and clinically-proven results make this a standout choice in the K-beauty brightening category. If you're ready for stronger results, consider graduating to the 23% version.

Product Overview

question
lightbulb What are Quick Product Notes?

Quick product notes are a great way to check if a product is free from commonly avoided ingredients by skincare enthusiasts. These preferences come about for different reasons depending on the ingredient such as personal experiences, sensitivities, health preferences & etc.

muscle Pro Tip Alert!

Just because a product is not free from a common preference does not mean it's a bad product! You can make a personal decision whether or not you want to use a product that contains these ingredients or not - click the labels of the preference to read more about them.

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Quick Product Notes

Click on icons for more information
question
lightbulb What are Notable Effects & Ingredients?

Ever used a product that promised a certain effect but provided no results? It might not have contained any notable ingredients that could have been responsible for that promised effect. It doesn't matter what the marketing or packaging «promises» it can do, if it doesn't contain anything that can help - then the likelihood of it helping is low.

We help you identify key notable ingredients that have been shown to help with effects such as acne-fighting, brightening, UV-protection, wound healing & anti-aging to help you achieve your skincare goals smarter. Please note that different notable ingredients have varying levels of research behind them, some are extremely well proven yet some have mixed research in their efficacy.

muscle Pro Tip Alert!

Just because a product doesn't contain any notable ingredients doesn't mean it's bad. And a product with notable ingredients (or even many) doesn't necessarily guarantee the efficacy of the product performing these effects either. There are other factors such as ingredient quality, concentration and formulation that will ultimately determine this.

Be smart and use this as just a starting point for you to make more informed and smarter choices and compare it with reviews to see if the product is right for you

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Notable Effects & Ingredients

anti-aging Anti-Aging from 5 ingredient(s):
Ascorbic Acid Caffeine Adenosine Tocopherol Niacinamide
brightening Brightening from 4 ingredient(s):
Ascorbic Acid Acetyl Glucosamine Glutathione Niacinamide
wound Promotes Wound Healing from 8 ingredient(s):
Ascorbic Acid Panthenol Sodium Hyaluronate Adenosine Allantoin Tocopherol Arginine Niacinamide
ache Ache-fighting from 1 ingredient(s):
Niacinamide
question
lightbulb What are Ingredients Related to Skin Type?

Why are some products great for some people and horrible for others? Well everyone has different skin types and different reactions to the same ingredients.

We've identified a range of ingredients that are commonly regarded as potentially good or bad for those with Dry, Oily/Acne-Prone or Sensitive skin.

muscle Pro Tip Alert!

A product that contains good or bad ingredients for your skin type doesn't always flat out make the entire product good or bad for your skin. There are other factors such as ingredient quality, concentration and formulation that will ultimately determine your skins reaction.

One of the best ways to use this section is to troubleshoot products you've had bad experiences with in the past. Check if it contains any of the marked ingredients to point out suspect ingredients to avoid in the future!

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Ingredients Related to Skin Types

Click on icons for more information
dry-skin Dry Skin
5
oily-skin Oily/Acne-Prone Skin
2
sensitive-skin Sensitive Skin
1
question
lightbulb What is the Ingredient Safety Breakdown?

Ingredient Safety Breakdown refers to the percentage % of ingredients in different risk categories as classified by EWG (Environment Working Group) if they are available. There are almost endless cosmetic ingredients and they are one of the few organisations globally that have assigned ratings to a lot of the more commonly used ingredients which is why we reference them.

muscle Pro Tip Alert!

EWG is seen by many to be more on the alarmist side in their assignment of health ratings resulting in rating ingredients as riskier than they actually are. We recommend using this a reference point rather than a strict guide of ingredient safety and to always do further research if into ingredients that you may find suspect.

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Ingredient Safety Breakdown

EWG Health Ratings
Low risk
Medium risk
High risk
Unknown risk
73% 26%

Product ingredient list

Showing first 5 of 23 ingredients
EWG CIR Ingredient Name & Cosmetic Functions Notes
1 Unknown
Water
Solvent, Skin Conditioning
1 A
Ascorbic Acid
Skin Conditioning, Masking, Fragrance, Antioxidant, Ph Adjuster, Buffering Agent, Buffering
brightening Brightening
anti-aging Anti-Aging
Promotes Wound Healing
Redness
Dark Spots
Texture
Pores
1 A
Butylene Glycol
Solvent, Skin Conditioning, Masking, Fragrance, Humectant, Viscosity Controlling, Viscositydecreasing Agent
Hydrating
1 A
Dipropylene Glycol
Fragrance, Solvent, Viscosity Decreasing Agent, Masking, Viscosity Controlling
0 Unknown
Tromethamine
VIEW ALL INGREDIENTS