Vitamin C serum in the morning, before sunscreen: the form matters as much as the percentage
A vitamin C serum is often the first active people add to a morning routine, just before sunscreen. But not all vitamin C is the same. The form of the ingredient matters as much as the percentage on the label. This guide explains what vitamin C is, how it works and how to use it, without hype or promises.
What vitamin C does in your skincare
Vitamin C is an antioxidant. That means it helps neutralise free radicals, unstable molecules your skin meets every day through sun exposure and pollution.
Because your skin is most exposed during the day, the morning is a sensible time for an antioxidant. It is also an ingredient associated with a more even, brighter-looking tone, with regular use and patience.
Important: vitamin C does not replace sunscreen. It complements it. Sunscreen is still the step that protects your skin from UV radiation.
Vitamin C serum in the morning: what order?
The practical rule is simple: lightest textures first, richer ones after. So a serum goes before your moisturiser.
- Cleanse gently.
- Vitamin C serum, a small amount.
- Moisturiser, to support hydration and comfort.
- Sunscreen, always the last step of the morning.
The form of vitamin C matters as much as the percentage
On an ingredients list (INCI), vitamin C appears under different names. Each behaves differently.
L-ascorbic acid
This is the «pure» form and the most studied. It is also the least stable: it reacts to light, air and heat. That is why it usually needs a well-sealed, opaque container, and it tends to be more irritating on sensitive skin.
Vitamin C derivatives
These appear in the INCI as ascorbyl glucoside, magnesium ascorbyl phosphate or sodium ascorbyl phosphate. They are generally more stable and gentler. The trade-off is that your skin has to convert them to reach the active form.
So a high percentage does not guarantee a better experience. A form your skin tolerates, kept stable in suitable packaging, can be more useful than a high number that irritates or spoils quickly.
A routine by type of ingredient
- Antioxidants (such as vitamin C): in the morning, before moisturiser and sunscreen.
- Hydrators (humectants such as glycerin or hyaluronic acid): morning and evening.
- Renewing actives (acids, retinoids): usually in the evening, introduced gradually.
- Sunscreen: every morning, reapplied through the day depending on exposure.
How to tell if your vitamin C has oxidised
Oxidation happens when the ingredient reacts with air and light and loses part of its function. Look for these signs:
- The colour darkens clearly (from yellow to orange or brown).
- The smell changes from when you opened it.
- The texture feels different, or it stings more than usual.
Note: some formulas have their own colour from the start, and derivatives may not change colour at all. Check what the manufacturer says and respect the period-after-opening symbol. To slow oxidation, close the container tightly and keep it away from heat and light.
Common myths
- «The higher the percentage, the better.» Not necessarily. Stability and tolerance matter a lot.
- «I use vitamin C, so I can skip sunscreen.» False. They do different jobs.
- «If it stings, it is working.» No. Stinging is not a sign of effectiveness.
When to talk to a dermatologist
See a professional if you have persistent redness, burning that does not settle, inflamed active acne, marks that change shape or colour, or if you are managing melasma. If you are unsure about a mark, do not wait.
Frequently asked questions
Does vitamin C go before sunscreen?
Yes. Apply it after cleansing and before moisturiser, and always finish with sunscreen.
Does a serum go before or after moisturiser?
Before. Lighter textures go on first.
What kind of active should I look for if I have sensitive skin but want results?
Start with one active at a time, introduce it slowly and on alternate days. A gentler form of vitamin C may be easier to tolerate. If irritation appears, stop and ask a dermatologist.
How do I know if my vitamin C serum has oxidised?
Look for a darker colour, a change in smell or texture, and check the period after opening.
Want to tailor your routine? Try the skin diagnosis, see how to use each step and find more tips in #TipOfTheDay.
Not sure which ingredients suit your skin? The skin diagnosis helps you see where to start.