There are many consequences that fentanyl can have on the human body. Fentanyl works by binding to the body's opioid receptors, which are found in the areas of the brain that control emotions and pain. Fentanyl causes a numbing feeling and after a while, the body adapts to the drug and begins to lose its sensitivity making it hard to feel pleasure from anything other than the drug. The only way to continue feeling this is by taking a larger and larger dose, which forms an addiction or reliance on the drug. When people becoming addicted, it's very difficult to stop because of the withdrawl effects and eventually, after a long enough period, you can overdose on fentanyl and potentially die. 

The only way to reverse an overdose is Narcan, but sometimes the drug can be even more powerful than the narcan that it is available which will lead to death. Even if you are not purposely taking fentanyl, many drug dealers are now mixing fentanyl with other drugs such as heroin, cocaine, methamphetamine and more. This is because it's easier to get high with fentanyl than with other drugs and drug dealers can sell less product for a greater profit. Keeping all of this in mind, please make sure to stay safe and be mindful of what you consume, drink, and receive from others.