The Ordinary Vitamin C: Which Product Should You Actually Use?

Vitamin C is one of the most researched and well-evidenced ingredients in skincare. It brightens, it protects against environmental damage, it supports collagen production, and it targets hyperpigmentation. The Ordinary sells six different Vitamin C products — and that's where the confusion starts.

Are they all the same? Which is most effective? Which one should a beginner start with? Why does it matter whether it's "pure" or a "derivative"? This guide answers all of those questions.

The two categories: pure Vitamin C vs. derivatives

All of The Ordinary's Vitamin C products fall into one of two categories, and this distinction is the most important thing to understand before choosing one.

Pure Vitamin C (L-Ascorbic Acid)

L-Ascorbic Acid (LAA) is the direct, active form of Vitamin C used in skincare research. It is the form your skin can use immediately without any conversion. It is also the most potent form — and the most unstable and irritating.

The Ordinary's pure Vitamin C products:

100% L-Ascorbic Acid Powder — Almost entirely pure LAA in powder form. You mix a tiny amount into another treatment immediately before applying. This is the most potent delivery method possible but requires care to avoid overdoing it.
Vitamin C Suspension 23% + HA Spheres 2% — 23% L-Ascorbic Acid in a direct suspension, plus Hyaluronic Acid spheres. The texture is gritty and slightly unusual. Effective but can sting, especially on sensitive skin.
Vitamin C Suspension 30% in Silicone — 30% L-Ascorbic Acid in a silicone base. Smoother feel than the 23% version. The silicone slightly reduces how directly the Vitamin C is delivered but improves wearability.

The key downside of pure Vitamin C: It is highly unstable and conflicts with several other active ingredients. It oxidises quickly on exposure to air and light (turning the product orange/brown), and it reacts with Niacinamide, Peptides, EUK 134, and direct acids in ways that reduce its effectiveness or cause irritation.

Vitamin C Derivatives

Derivatives are modified forms of Vitamin C that are more stable in formula and gentler on skin. Your skin converts them to active Vitamin C after absorption. They don't deliver the same immediate potency as pure LAA but are significantly easier to use.

The Ordinary's Vitamin C derivative products:

Ascorbyl Glucoside Solution 12% — A water-based serum using Ascorbyl Glucoside, widely considered the gold-standard Vitamin C derivative. Highly stable, suitable for AM and PM, and it only conflicts with Niacinamide (unlike pure Vitamin C which conflicts with far more ingredients).
Ascorbyl Tetraisopalmitate Solution 20% in Vitamin F — An oil-soluble derivative in a base of essential fatty acids (Vitamin F). Very stable and particularly beneficial for dry or compromised skin types.
Magnesium Ascorbyl Phosphate 10% — A water-soluble derivative in a cream/emulsion format. High stability, brightening, and well-suited to dry skin or those who find serums too drying.

The conflict problem with pure Vitamin C

If you are already using other active ingredients, pure Vitamin C creates a significant compatibility problem. Pure L-Ascorbic Acid (and its close relative Ethylated Ascorbic Acid) should not be used in the same routine as:

Niacinamide — Can cause flushing and reduces the efficacy of both ingredients. Keep them in separate routines (Vitamin C in PM, Niacinamide in AM).
Peptides (Buffet, Argireline, Matrixyl, Copper Peptides) — Pure Vitamin C can interfere with peptide activity.
EUK 134 0.1% — EUK 134 is a powerful antioxidant enzyme that is destabilised by the low pH of pure Vitamin C. Use them in separate routines.
Direct Acids (AHAs, BHAs) — Layering pure Vitamin C with exfoliating acids can cause significant irritation.
Retinoids — Use pure Vitamin C and retinoids in separate routines.
Copper Peptides — Vitamin C can interfere with the copper complex.

The derivative forms are much simpler. Ascorbyl Glucoside, for example, only conflicts with Niacinamide — everything else is fine. If you are building a complex routine with multiple actives, a derivative is almost always the better choice.

Which Vitamin C should you choose?

If you are new to Vitamin C

Start with Ascorbyl Glucoside Solution 12%. It is stable, effective, compatible with most other ingredients (only avoid Niacinamide in the same routine), and won't irritate your skin. Use it in the morning before your moisturiser.

If you want maximum brightening and anti-oxidant effect and your skin is used to actives

Vitamin C Suspension 23% + HA Spheres 2% or Vitamin C Suspension 30% in Silicone will give you the most potent delivery. Expect some tingling, particularly at first. Use in the PM to avoid interaction with other morning actives.

If you have dry skin or want an oil-based formula

Ascorbyl Tetraisopalmitate Solution 20% in Vitamin F works well layered within an oil-based routine. It's particularly good for those who prefer facial oils over water-based serums.

If you want to layer Vitamin C with other actives precisely

100% L-Ascorbic Acid Powder gives you total control over dosage. Mix a small amount into whichever serum you choose to apply immediately. Used properly, this is the most flexible high-potency option — but it requires attention to avoid over-application.

When to apply Vitamin C in your routine

Pure Vitamin C: In the PM. The conflict with Niacinamide and Peptides (both popular AM ingredients) makes PM the safer and more compatible slot.

Derivative Vitamin C: Can be used AM or PM. Many people use Ascorbyl Glucoside in the AM as an antioxidant layer before SPF.

In terms of layering order, Vitamin C products generally go on after any toner or essence, but before oils and moisturisers. Water-based Vitamin C serums come before oil-based ones.

Does Vitamin C turn orange — and is that a problem?

Pure L-Ascorbic Acid oxidises when exposed to light and air. A slightly yellow-tinted product is normal and still active. A product that has gone deep orange or brown has oxidised significantly and is past its best. Store your Vitamin C products in a cool, dark place and use them promptly after opening.

Derivatives are far more stable and do not have this issue to the same degree — another reason they are often the more practical choice.

How the Skincare Routine app manages Vitamin C conflicts for you

Tracking all of these compatibility rules manually is genuinely difficult, especially once you have a multi-step routine. The Skincare Routine app handles this automatically.

All six Vitamin C products from The Ordinary are pre-loaded with their full conflict data. When you tick off products during your morning or evening routine:

Red checkboxes appear next to products that would create a hard conflict — for example, if you've already ticked Niacinamide and then try to tick a pure Vitamin C product, the conflict is flagged immediately.
The app automatically suggests keeping pure Vitamin C in the PM and Niacinamide in the AM.
When you add a derivative Vitamin C, the app correctly flags only the Niacinamide conflict — not the longer list that applies to pure forms.

There's no need to memorise which form is which or which conflicts apply to each. Add your products and the app manages the rest.

The app is available on iOS and Android at skincareroutine.app.

Summary

Product	Type	Best for	When
100% L-Ascorbic Acid Powder	Pure LAA	Maximum potency, advanced users	PM
Vitamin C Suspension 23% + HA Spheres 2%	Pure LAA	High-strength direct delivery	PM
Vitamin C Suspension 30% in Silicone	Pure LAA	High-strength, smoother feel	PM
Ascorbyl Glucoside Solution 12%	Derivative	Beginners, complex routines	AM or PM
Ascorbyl Tetraisopalmitate 20% in Vitamin F	Derivative	Dry skin, oil-based routines	AM or PM
Magnesium Ascorbyl Phosphate 10%	Derivative	Dry skin, cream lovers	AM or PM

The single most useful rule: if you are already using Niacinamide, Peptides, or EUK 134, choose a derivative — and use the Skincare Routine app to keep track of the rest.