It is always a good idea to speak with your doctor about taking CBD oil for sleep, especially if you are already taking anything to help you sleep already. In general, everyone has their own unique experience with CBD when taken for sleep. Not one dosage, dosage time, or potency will affect everyone the same. CBD is not usually something that will cause an immediate difference; it can take some time to notice a difference. It is best to start out low and slow, monitor the outcome, and adjust as needed. If you are taking a combination like CBD and melatonin, it can be best to take the supplement a few hours before you go to bed.