Five minutes, then stop
Vitamin C Serum: Morning or Night?
Morning, under sunscreen, is the default. Night is allowed if the acid stings in the day. You do not need both clocks.
Updated 27 Aug 2026 · 6 min read · vitamin C serum morning or night
Why morning is the usual slot
L-ascorbic acid is an antioxidant. Daylight is the insult. Putting them in the same routine is the logic, not a commandment. A 10–15% L-ascorbic at pH ~3.5 is the classic; derivatives (ascorbyl glucoside, THD ascorbate, SAP) are more stable and often weaker, and can live AM or PM.
Wait until the serum is no longer tacky — 30–90 seconds — so you are not diluting SPF.
When night makes more sense
If the acid stings under makeup. If you only remember one treatment and it is a retinoid in the morning you will not wear SPF for — move C to night and keep the retinoid at night too, on alternate evenings, rather than a war at 7am.
| Formula | Clock |
|---|---|
| 10–20% L-ascorbic acid | AM default |
| Gentler derivative | AM or PM |
| C plus retinoid, same routine | Not as a default |
| C under tinted SPF | AM, let C set first |
The bottle dies louder than your face
Brown, orange, or a metallic smell: it has oxidized. Throw it. Dark dropper, cool cupboard, finish in 3 months. $12–$40 is the useful band. A $90 vitamin C that went rust-coloured in six weeks was still oxygen’s product.
Questions, answered
- Do I need vitamin C if I wear SPF?
- Need is a strong word. C is an extra. SPF is the non-negotiable. Do not skip SPF because the serum was expensive.
- Can I use it every day?
- If the face stays quiet, yes. If you flake, every other morning.
- Does it go over or under moisturizer?
- Under, on clean skin. Watery first.
