The serum is designed for day and night use, so you can apply it in both your morning and evening routine. However, retinol makes the skin more sensitive to UV radiation, so if you use it during the day, you must follow with a broad-spectrum sunscreen with at least SPF 30. Even on cloudy days or when you are mostly indoors, UV exposure adds up, so make sunscreen a non-negotiable step in your morning routine.
In the morning, a simple order works well: cleanse, apply the serum, wait a minute or two for it to absorb, then apply moisturizer and sunscreen. In the evening, you can use the serum after cleansing and before your night cream. If you prefer a lighter texture, the serum can be used alone around the under-eye area instead of a cream, but keep it away from the lash line and do not get it into the eyes.
If your skin is sensitive, you may choose to use the serum only in the evening and rely on a gentle moisturizer in the morning. That is perfectly fine — the product does not have to be used twice a day to be effective. Consistency matters more than frequency: using it regularly, even once daily, gives better results than using it twice a day for a few days and then stopping.
Remember that sunscreen is not optional with retinol. It protects the skin from sun damage and helps prevent the very signs of ageing the serum is meant to address.