Different varieties of cannabis plants — such as hemp and marijuana — contain different levels of chemical compounds. How people breed the plant affects the CBD levels. Most CBD oil comes from industrial hemp, which usually has a higher CBD content than marijuana. Makers of CBD oil use different methods to extract the compound. The extract is then added to a carrier oil and called CBD oil. CBD oil comes in many different strengths, and people use it in various ways. It is best to discuss CBD oil with a doctor before using it.