13 Best Drugstore Vitamin C Serums for Bright Skin, According to Experts

Concentration: “Vitamin C products range in concentrations from less than 5 percent up to 30 percent,” says Dr. Sara Hogan, MD, FAAD. “Most over-the-counter serums, if they disclose their formulation, are between 5 to 15 percent. It is thought that Vitamin C serums should have concentrations of 10 percent or higher to be effective, though studies have shown concentrations above 20 percent have potential for irritation without much added benefit.” If you have sensitive skin or are just trying out a vitamin C product, Dr. Gohara says it’s better to use a lower concentration and consider working your way up.

Ingredients: There are many different forms of vitamin C—choosing the form that will work best for your skin is important. “L-abscorbic acid is considered the most bioactive form, present in most drug store Vitamin C serums and appropriate for most skin types,” says Dr. Hogan. “If you have dry or mature skin, consider a serum containing lipid-soluble tetrahexyldecyl ascorbate since it can moisturize and brighten.”

Packaging: Vitamin C is an unstable ingredient, so packaging is important since light and air can destabilize it. According to Dr. Hogan, Vitamin C stored in opaque, airtight containers may be more stable and keep longer.