Use your azelaic acid product every other day, either in the morning before your sunscreen or at night, before your moisturizer.
You can use this product in the morning or at night, before your moisturizer or sunscreen. If your skin tolerates it well, you can use it twice a day.

Start slowly with this product: it can be irritating, but your skin can adjust to it with time. It is best to start using this product only once a week for the first few weeks. Mild dryness is normal when starting using a retinoid. Once your skin is able to tolerate the product well, you can increase the frequency of use to twice, and even three times a week. Make sure to apply a moisturizer regularly when using this product. Apply this product on clean skin, before a moisturizer. Most people prefer using this product at night, but it can be used in the morning as well.