Apply vitamin C serum before your moisturizer, on clean, dry skin. That is the short answer. The reasons behind it will help you get more from every product in your routine.
Why serum goes before moisturizer
The usual rule is to layer from the thinnest texture to the thickest. Serums are light and water-based, and they carry a high concentration of actives. Moisturizers are richer and are meant to seal hydration in. If you put the moisturizer on first, it sits between your skin and the serum, and less of the vitamin C gets where it needs to go.
So the order is: cleanse, vitamin C serum, eye cream, moisturizer, and sunscreen in the morning.
Morning or night?
Vitamin C is an antioxidant. It helps neutralize the free radicals caused by UV light and pollution, which makes the morning the most useful time for it. Under sunscreen, it adds a second layer of defence. It still brightens skin if you use it at night, so pick the time you will actually stick to.
How long to wait between layers
Give the serum a minute to absorb before you add moisturizer. You don’t need to wait longer than that for most formulas.
What if my moisturizer already has vitamin C?
Then your moisturizer can be your vitamin C step. The Biostem Daily Moisture Complex contains two stable sources of vitamin C alongside azelaic acid and arbutin, so it evens tone while it hydrates. If you use a serum as well, apply the serum first and the moisturizer after. The Biostem Serum also contains a stable vitamin C, so the two layer well.
Which type of vitamin C?
Pure vitamin C (L-ascorbic acid) is well studied but breaks down quickly and can sting sensitive skin. Derivatives such as magnesium ascorbyl phosphate (MAP) are more stable and gentler. We cover MAP in detail in Vitamin C for sensitive skin: meet MAP.
Can I use vitamin C with niacinamide?
Yes. An older idea held that the two cancel each other out, but that was based on lab conditions very different from skin. Most people can use them together or one after the other. Read more in our niacinamide guide.
Frequently asked questions
Do I apply vitamin C serum before or after moisturizer?
Before. Serum first, on clean skin, then moisturizer.
Should vitamin C go before or after sunscreen?
Before. Sunscreen is always the last step of a morning routine.
Can I use vitamin C every day?
Most people can. If your skin is sensitive, start every other day, or choose a gentle derivative such as MAP.