There are several ways that fentanyl can be introduced into the body. One of those ways is when dealers combine fentanyl with other substances, such as heroin. They do this because combining fentanyl with heroin increases the effects of it. It also increases the supply and decreases the costs. However, people can also take it directly. They might do this by snorting or sniffing. They could also take it orally with a pill mimicking a prescription. It can also be smoked or injected.