I started incorporating this serum in my morning at the end of December 2021 and until now it's been 3 weeks. In this short period, I notice a great improvement in my skin tone. I have an acne prone skin and also suffer with hyperpigmentation but it doesnt break me out and I dont notice much different with the mark and scar. However, I think it takes more time, probably finish this whole bottle to see the result for post acne mark improvement. Would recommend to all skin types but if you're new to niacinamide, please start slowly and DO PATCH TEST!