One of the biggest complaints with fentanyl withdrawal
is the powerful hot flashes and cold sweats. It happens if you're either over- or under-medicated. This happens when withdrawing from any kind of opiate, but fentanyl seems to make it even worse. Other symptoms include nausea/ vomiting, diarrhea, lack of appetite, restless leg syndrome and muscle cramps, generalized pain throughout the body, and terrible insomnia.