You can start using it after 20s. I use Anveya's vitamin C serum. It helps in keeping the face hydrated and moist. It has anti ageing properties and treats pigmentation. It's really worth trying.

Dear try out Anveya vitamin c face serum start from 30s itself it gives good glow on face and reduces blemishes and pigments too

After 25 one can start using Vitamin C serum , try from a good brand like Anveya , it's good , regular usage improves skin condition and make skin feel and look better.

According to the study in Nutrients, vitamin C can help protect the skin from many problems, including sunburn, photoaging, hyperpigmentation, wrinkles, sagging, dryness, and an uneven skin tone. Anyone dealing with these skin issues may want to consider adding a vitamin C serum to their skincare regimen. If you're wondering when to apply a vitamin C serum, the answer is both morning and night, after cleansing and toning. One study even recommends applying a vitamin C serum every eight hours, or twice daily for the pinnacle of protection.