How to Know If Your Vitamin C Serum Is Doing Its Job + What to Expect Vitamin C is one of the most-loved ingredients in skincare brightening, antioxidant protection, fading dark spots. But often people wonder: Is my Vitamin C serum really working? What changes should you look for and when? Here’s your guide to spotting the signs, avoiding pitfalls, and getting the glow you want. What Happens When a Vitamin C Serum Works If you use it consistently and correctly, here's what usually shows up week by week: Time Period What You Might Notice Week 1–2 Your skin feels more hydrated, looks a little fresher. Maybe less dullness, slightly smoother. Week 2–4 A more even skin tone; early dark spots or hyperpigmentation may begin to fade; red patches calm down. Week 4–8 Skin texture improves; pores or fine lines appear softer; overall radiance is more visible. After ~12 weeks (3 months) More significant brightening; pigmentation or dark spots are noticeably lighter; skin barrier stronger; r...