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Guide

Vitamin C forms explained: L-ascorbic acid vs the derivatives

Short answer: L-ascorbic acid is the form with the most research, but it only gets into skin from a very acidic formula and it oxidizes easily. Derivatives such as ascorbyl glucoside are steadier and gentler, with weaker evidence. Sensitive skin should usually start with a derivative.

Three serum swatches from clear to gritty on white marble between orange peel curls and a halved kumquat
Illustration (AI-generated; no real products shown).
By PickedSkincare Editorial TeamLast updated Prices checked: November 2026

Checked against brand ingredient lists on and against dermatology sources (American Academy of Dermatology, FDA, peer-reviewed studies). How we research · Editorial policy · 10 sources

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How this page was made: we compared what each brand publishes (actives, strengths, full ingredient lists, directions and prices) and checked the claims against dermatology guidance and published studies, all linked at the bottom. We haven’t tested these products on our own skin, we don’t publish star ratings, and a commission never decides a pick. Our methodology.

Not medical advice. This page compares cosmetic products. If you have a skin condition, use prescription treatment, or are pregnant or breastfeeding, ask a dermatologist or your doctor before starting something new.

Short answer

L-ascorbic acid is the form with the most research, but it only gets into skin from a very acidic formula and it oxidizes easily. Derivatives such as ascorbyl glucoside are steadier and gentler, with weaker evidence. Sensitive skin should usually start with a derivative.

Last updated Ingredient lists checked 2026-11-11Prices checked November 2026

The numbers side by side

Summary of this page’s sourced guidance
In brief
The rule of thumbL-ascorbic acid is the form with the most research, but it only gets into skin from a very acidic formula and it oxidizes easily. Derivatives such as ascorbyl glucoside are steadier and gentler, with weaker evidence.
Spending lessThe cheapest direct vitamin C we found is The Ordinary Vitamin C Suspension 23% at $8.10 for 30 ml. The gentlest cheap derivative is The Ordinary Ascorbyl Glucoside Solution 12% at $14.80.

“Vitamin C” on a label can mean several different molecules. The form decides how stable the serum is, how much it stings and how much research backs it. We read the key studies and the ingredient lists of five vitamin C products. We haven’t tested them ourselves.

Table of the 5 products on this page with brand price and key actives: The Ordinary Vitamin C Suspension 23% + HA Spheres 2%, $8.10, L-ascorbic acid 23% (brand-stated), sodium hyaluronate; SkinCeuticals C E Ferulic, No brand-site price, L-ascorbic acid 15%, alpha tocopherol 1%, ferulic acid 0.5%, plus carnosine 0.3% and “Endophytol” 1% in the current formula (all brand-stated); Paula’s Choice C15 Super Booster, $59.00, 15% pure vitamin C (ascorbic acid), brand-stated; The Ordinary Ascorbyl Glucoside Solution 12%, $14.80, Ascorbyl glucoside 12% (brand-stated; a vitamin C derivative); Naturium Vitamin C Complex Serum, $21.00, Sodium ascorbyl phosphate and ascorbic acid (combined percentage not stated on the page we checked), glutathione.
Products covered on this page, from each brand’s own product page (checked November 11, 2026).
Chart of brand-stated ingredient percentages on a log scale. The Ordinary Vitamin C Suspension 23% + HA Spheres 2%: L-ascorbic acid 23%; SkinCeuticals C E Ferulic: L-ascorbic acid 15%, alpha tocopherol 1%, ferulic acid 0.5%, carnosine 0.3%; Paula’s Choice C15 Super Booster: no single-ingredient percentage stated; The Ordinary Ascorbyl Glucoside Solution 12%: Ascorbyl glucoside 12%; Naturium Vitamin C Complex Serum: no single-ingredient percentage stated.
Brand-stated percentages only. Different ingredients aren’t equal per percent, so compare like with like.

What’s in each bottle?

Copied from each brand’s own product page (or the sunscreen’s Drug Facts) on November 11, 2026. Brands reformulate, so the carton in your hand is the final word.

The Ordinary Vitamin C Suspension 23% + HA Spheres 2%

Key actives
L-ascorbic acid 23% (brand-stated), sodium hyaluronate
Base
Water-free silicone/ester suspension (slightly gritty)
Brand price
$8.10 · 30 ml
Brand notes
Brand: tingling can be expected; can be diluted into a cream; patch test advised; not to be used in the same routine as its niacinamide, retinoids, peptides or direct acids.
Full ingredient list

Ascorbic Acid, Squalane, Isodecyl Neopentanoate, Isononyl Isononanoate, Coconut Alkanes, Ethylene/Propylene/Styrene Copolymer, Ethylhexyl Palmitate, Silica Dimethyl Silylate, Sodium Hyaluronate, Glucomannan, Coco-Caprylate/Caprate, Butylene/Ethylene/Styrene Copolymer, Acrylates/Ethylhexyl Acrylate Crosspolymer, Trihydroxystearin, BHT.

The Ordinary product page · Check price on Amazon (opens in a new tab)

SkinCeuticals C E Ferulic

Key actives
L-ascorbic acid 15%, alpha tocopherol 1%, ferulic acid 0.5%, plus carnosine 0.3% and “Endophytol” 1% in the current formula (all brand-stated)
Base
Water-based serum
Brand price
Not sold on the brand site; check a retailer
Brand notes
Brand: fragrance-free, paraben-free, alcohol-free; darkens with air and light; use within 3–6 months of opening.
Full ingredient list

Full list not shown in the page text we could read; see the brand page.

SkinCeuticals product page · Check price on Amazon (opens in a new tab)

Paula’s Choice C15 Super Booster

Key actives
15% pure vitamin C (ascorbic acid), brand-stated
Base
Water-based booster that can be mixed into serum or non-SPF moisturizer
Brand price
$59.00
Brand notes
Brand FAQ: can be used in the same routine as niacinamide; use vitamin C in the morning and retinol at night; color can range from clear to pale peach as it ages.
Full ingredient list

Full list not shown in the page text we could read; see the brand page.

Paula’s Choice product page · Check price on Amazon (opens in a new tab)

The Ordinary Ascorbyl Glucoside Solution 12%

Key actives
Ascorbyl glucoside 12% (brand-stated; a vitamin C derivative)
Base
Water-based solution
Brand price
$14.80 · 30 ml
Full ingredient list

Aqua (Water), Ascorbyl Glucoside, Propanediol, Aminomethyl Propanol, Triethanolamine, Isoceteth-20, Xanthan Gum, Dimethyl Isosorbide, Ethoxydiglycol, Trisodium Ethylenediamine Disuccinate, 1,2-Hexanediol, Caprylyl Glycol.

The Ordinary product page · Check price on Amazon (opens in a new tab)

Naturium Vitamin C Complex Serum

Key actives
Sodium ascorbyl phosphate and ascorbic acid (combined percentage not stated on the page we checked), glutathione
Base
Water-based serum
Brand price
$21.00 · 1.0 fl oz
Brand notes
Brand advises a patch test and SPF in the morning.
Full ingredient list

Water (Aqua), Glycerin, Propanediol, Sodium Ascorbyl Phosphate, Ascorbic Acid, Glutathione, Ananas Sativus (Pineapple) Fruit Extract, Carica Papaya (Papaya) Fruit Extract, Mangifera Indica (Mango) Fruit Extract, Terminalia Ferdinandiana Fruit Extract, Pleiogynium Timoriense Fruit Extract, Podocarpus Elatus Fruit Extract, Aloe Barbadensis Leaf Juice, Sodium Hyaluronate, Carbomer, Tocopheryl Acetate, Phenoxyethanol, Caprylyl Glycol, Citric Acid, Hydroxyethylcellulose, Sodium Hydroxide, Beta-Glucan, Potassium Sorbate, Hexylene Glycol, Sorbitol, Xanthan Gum, Algin, Benzoic Acid, Sorbic Acid, 1,2-Hexanediol, Sodium Benzoate, Disodium Phosphate, Gold, Polysorbate 60, Sodium Phosphate.

Naturium product page · Check price on Amazon (opens in a new tab)

Which vitamin C forms will you see on labels?

Vitamin C forms in the products we checked (brand ingredient lists, November 11, 2026)
Name on the labelWhat it isExample product
Ascorbic acid (L-ascorbic acid)Pure vitamin C; “direct” formThe Ordinary Vitamin C Suspension 23%; SkinCeuticals C E Ferulic (15%); Paula’s Choice C15 (15%)
Ascorbyl glucosideWater-soluble derivative that converts to vitamin C on skin, per The OrdinaryThe Ordinary Ascorbyl Glucoside Solution 12%
Sodium ascorbyl phosphateWater-soluble derivativeNaturium Vitamin C Complex (with ascorbic acid)

What does the research say?

  • pH matters: Pinnell[1] et al. (2001) found L-ascorbic acid must be formulated below pH 3.5 to enter skin, with absorption peaking at 20%. Skin levels saturated after three daily applications.
  • Some derivatives didn’t deliver: in the same study, magnesium ascorbyl phosphate, ascorbyl-6-palmitate and dehydroascorbic acid did not raise skin vitamin C levels. Ascorbyl glucoside and sodium ascorbyl phosphate weren’t tested there.
  • Stabilizers help: Lin[2] et al. (2005) found adding 0.5% ferulic acid to 15% L-ascorbic acid plus 1% vitamin E improved stability and doubled photoprotection in skin from about 4-fold to 8-fold. That is the formula SkinCeuticals sells as C E Ferulic.
  • The honest caveat: a 2017 review by Al-Niaimi[3] and Chiang says clinical studies of topical vitamin C formulas remain limited, and the challenge is finding a stable, absorbable formula.

Which form suits your skin?

  • Sensitive or new to vitamin C: a derivative such as ascorbyl glucoside. The Ordinary itself says direct vitamin C “may not be ideal for sensitive skin”.
  • Oily, tolerant skin: L-ascorbic acid at 10% to 20%; above 20% there’s no added absorption per Pinnell[1].
  • Dry skin: a water-free or oil-soluble format feels kinder; The Ordinary’s 23% suspension sits in squalane and esters.
  • Always: morning use under sunscreen, per the AAD’s[5] routine advice.

How can you tell a vitamin C serum has gone off?

L-ascorbic acid oxidizes with air, light and water. SkinCeuticals says C E Ferulic darkens over time and should be used within 3 to 6 months of opening; Paula’s Choice says C15 can range from clear to pale peach as it ages. A water-free formula, like The Ordinary’s 23% suspension, avoids water altogether, which the brand says keeps it stable.

Decision diagram: Which vitamin C form fits your skin? Sensitive skin, or new to vitamin C? No → Fine with tingling from acidic serums? No → Start with a derivative, or dilute L-ascorbic acid in moisturizer. Sensitive skin, or new to vitamin C? No → Fine with tingling from acidic serums? Yes → L-ascorbic acid; absorption peaked at 20% in research (Pinnell 2001). Sensitive skin, or new to vitamin C? Yes → A gentler derivative such as ascorbyl glucoside, every morning. Use it in the morning, under SPF 30+. Vitamin C is not a sunscreen.
Which vitamin C form fits your skin? A simplified path drawn from the guidance and sources on our vitamin C pages; it isn’t a diagnosis.
Routine order diagram. Morning: 1. Cleanse, 2. Treatment serum (The Ordinary Vitamin C Suspension 23% + HA Spheres 2%, SkinCeuticals C E Ferulic, Paula’s Choice C15 Super Booster, The Ordinary Ascorbyl Glucoside Solution 12%, Naturium Vitamin C Complex Serum), 3. Moisturizer, 4. Sunscreen, SPF 30+. Night: 1. Cleanse, 2. Treatment, 3. Moisturizer.
Routine order following AAD guidance; highlighted steps are where this page’s products go.

Who should skip it?

  • Sensitive skin starting with 20%+ L-ascorbic acid: The Ordinary warns tingling is expected with its 23% and that direct vitamin C may not suit sensitive skin. Consider instead: ascorbyl glucoside 12%.
  • Paying for more than 20% L-ascorbic acid: Pinnell[1] et al. found absorption peaked at 20%.
  • Expecting vitamin C to replace sunscreen: The AAD[5] routine places vitamin C under sunscreen, not instead of it.

How can you spend less?

The cheapest direct vitamin C we found is The Ordinary Vitamin C Suspension 23% at $8.10 for 30 ml. The gentlest cheap derivative is The Ordinary Ascorbyl Glucoside Solution 12% at $14.80.

What should you know before you start?

What do people ask most?

Which form of vitamin C is best?
L-ascorbic acid has the most research, but only works from an acidic, well-made formula. For sensitive skin a derivative is often the better trade-off.
What percentage of vitamin C should I use?
Pinnell[1] et al. found skin absorption of L-ascorbic acid peaked at 20%; The Ordinary advises beginners to start lower and build tolerance.
Why did my vitamin C serum turn orange?
L-ascorbic acid oxidizes. SkinCeuticals says darkening is expected and to use C E Ferulic within 3 to 6 months of opening.
Is ascorbyl glucoside as good as L-ascorbic acid?
The Ordinary says it is more stable in water but less potent than L-ascorbic acid. We didn’t find a head-to-head trial.

Where this comes from

We opened and read every source below for this page. Ingredient lists, strengths, directions and prices come from each brand’s own product page; health and usage guidance comes from the American Academy of Dermatology, the FDA, the National Eczema Association and peer-reviewed studies (via PubMed). Prices checked: November 2026; confirm on the seller’s site before you buy.

  1. Pinnell et al. 2001, Dermatologic Surgery: Topical L-ascorbic acid percutaneous absorption (pubmed.ncbi.nlm.nih.gov)
  2. Lin et al. 2005, Journal of Investigative Dermatology: Ferulic acid stabilizes vitamins C and E (pubmed.ncbi.nlm.nih.gov)
  3. Al-Niaimi & Chiang 2017, Journal of Clinical and Aesthetic Dermatology: Topical vitamin C and the skin (pubmed.ncbi.nlm.nih.gov)
  4. The Ordinary (brand guide): Vitamin C in skincare, direct vs derivative forms (theordinary.com)
  5. AAD: Dermatologist-recommended skin care for your 20s (aad.org)
  6. The Ordinary (brand page): The Ordinary Vitamin C Suspension 23% + HA Spheres 2% (theordinary.com)
  7. The Ordinary (brand page): The Ordinary Ascorbyl Glucoside Solution 12% (theordinary.com)
  8. SkinCeuticals (brand page): SkinCeuticals C E Ferulic (skinceuticals.com)
  9. Paula’s Choice (brand page): Paula’s Choice C15 Super Booster (paulaschoice.com)
  10. Naturium (brand page): Naturium Vitamin C Complex Serum (naturium.com)
comparison

The Ordinary Vitamin C Suspension 23% vs SkinCeuticals C E Ferulic

Both are pure L-ascorbic acid. The Ordinary suspends 23% in a water-free base for $8.10 and warns it tingles; SkinCeuticals pairs 15% with vitamin E and ferulic acid, the combination tested in a 2005 peer-reviewed study, at a much higher price.

comparison

The Ordinary Ascorbyl Glucoside Solution 12% vs Vitamin C Suspension 23%

Same brand, opposite approaches. Ascorbyl Glucoside 12% is a water-based derivative the brand calls lower in irritation potential but less potent; Vitamin C Suspension 23% is pure L-ascorbic acid in a water-free base that the brand says will tingle.

guide

Niacinamide vs vitamin C for dark spots: which should you try first?

Short answer: start with daily sunscreen (tinted, if you have a darker skin tone), then add one product. Niacinamide is the gentler first try with clearer clinical data on spots; L-ascorbic acid vitamin C is the stronger antioxidant but can sting.

guide

Can you use niacinamide with vitamin C or retinol?

Short answer: niacinamide with retinol is widely accepted; even Paula’s Choice says they pair well. Niacinamide with vitamin C is where brands disagree, so the simple default is vitamin C in the morning and niacinamide or retinol at night.

comparison

La Roche-Posay Anthelios Ultra Light Fluid SPF 60 vs EltaMD UV Clear SPF 46

Anthelios uses four chemical filters (avobenzone, homosalate, octisalate, octocrylene), is water resistant for 80 minutes and costs $35.99. UV Clear pairs zinc oxide 9% with octinoxate 7.5%, adds 5% niacinamide, is aimed at sensitive, rosacea- and acne-prone skin, isn’t water resistant and costs $46 for 1.7 oz.