A good vitamin C serum is one of the best-studied ways to brighten dull skin, fade dark spots, and add a layer of antioxidant defence against daily damage. But vitamin C is also finicky — the wrong form, the wrong storage, or the wrong order in your routine can waste most of what you paid for.
Which form of vitamin C to look for
The most researched form is L-ascorbic acid, usually most effective at 10–20%. It's powerful but unstable — it oxidises when exposed to air and light (a serum turning dark orange means it's degrading). If your skin is sensitive or you want something more stable, gentler derivatives like sodium ascorbyl phosphate or magnesium ascorbyl phosphate are good alternatives.
Use it in the morning
Vitamin C shines in your morning routine: apply it after cleansing, before moisturiser and sunscreen. Paired underneath SPF, it boosts your daytime protection against free radicals. Cleanse, vitamin C, moisturiser, sunscreen — in that order.
Storage is half the battle
Keep the bottle away from sunlight and tightly closed. Opaque or air-restrictive packaging is a good sign. If your serum has gone deep orange or brown, its potency has dropped — a fresh, pale, straw-coloured serum is what you want.
Combining vitamin C with other actives
- With sunscreen: a perfect morning pair — C then SPF.
- With niacinamide: fine in modern formulas; if you're worried, use one morning and one night.
- With retinol: keep C for mornings and retinol for nights to avoid over-irritation.
Be patient and consistent
Brightening and fading of dark spots is gradual — expect meaningful change over 8 to 12 weeks of daily use. Consistency, correct storage, and daily sunscreen do more than jumping to a higher percentage.
See vitamin C serums we've tested and scored, or ask an expert which form suits your skin.
FAQ
Should I use vitamin C in the morning or at night?
Morning is ideal — under sunscreen it adds antioxidant protection against daytime free-radical damage. Apply it after cleansing and before moisturiser and SPF.
My vitamin C serum turned orange — is it still good?
A deep orange or brown colour means it has oxidised and lost potency. A fresh serum is pale and straw-coloured; store it away from light and air.
Can I use vitamin C and niacinamide together?
Yes. The old myth that they cancel out doesn't hold for modern formulas. If your skin is sensitive, you can simply use one in the morning and the other at night.
How long until a vitamin C serum shows results?
Give it 8 to 12 weeks of consistent daily use for visible brightening and fading of dark spots. Correct storage and daily SPF matter more than a higher percentage.