Vitamin C powder or a premixed serum?

What are the practical differences?

Choose a premixed serum if you want fewer steps and a stated strength, rather than a skincare routine with a mixing assignment. Choose powder if you specifically want to adjust the amount and are willing to follow its mixing and compatibility directions. Sensitive skin is a reason to be cautious with either format, not a reason to assume powder is gentler.12

The formula matters more than the format

L ascorbic acid is the best studied form of topical vitamin C. Its delivery depends on concentration, acidity, stability and the base carrying it into skin. For conventional L ascorbic acid formulas, a pH below 3.5 helps penetration. Vitamin E and ferulic acid are useful formulation partners; ferulic acid can also help stabilize L ascorbic acid.234

More concentrated does not automatically mean more useful. Concentrations above 20% do not add biological benefit and can increase irritation. Vitamin C derivatives have different chemistry and stability, so their percentages are not interchangeable with L ascorbic acid percentages.3

Premixed does not automatically mean well formulated, either. L ascorbic acid is unstable when exposed to oxygen, and some formulas do not deliver enough vitamin C into skin. A vitamin C claim on the bottle is not the same thing as an effective formula, however confidently the bottle introduces itself.5

How do you use a premixed serum?

1. 1Wash with a gentle cleanser in the morning.
2. 2Apply a few drops of vitamin C serum to your face and neck, following its label.
3. 3Apply moisturizer, then sunscreen. Choose broad spectrum SPF 30 or higher with water resistance for outdoor exposure.

You can begin every other day and increase to daily use if tolerated. Vitamin C complements sunscreen; it does not replace it.2

How do you use vitamin C powder?

For The Ordinary's 100% L Ascorbic Acid Powder:

1. 1Patch test before facial use. Apply a small amount to clean skin on the upper forearm, keep dry and rinse after 24 hours. Do not use if redness, burning, itching, blistering or irritation develops.
2. 2Mix a small amount with a compatible serum, cream or moisturizer in your palm.
3. 3Apply to unbroken facial skin once daily, ideally in the evening. Avoid the eye area and eye contact.
4. 4Use sun protection during the day.

The Ordinary tells you not to use this powder with niacinamide, retinoids, direct acids, other direct vitamin C, peptides, copper peptides, EUK or GF 15% Solution. These are directions for this powder, not a universal ban on those ingredients in every vitamin C routine.1

What should you expect?

Topical vitamin C can improve fine lines and skin texture, and may help fade dark spots. Allow up to three months of consistent use for noticeable improvement. Mild tingling can occur. With The Ordinary's powder, reduce the amount if tingling is too strong; if irritation occurs, rinse off, stop using it and consult a physician. Substantial discomfort or irritation from a serum also means stopping and contacting your doctor.12