Heavy Sweating
Profuse sweating is a symptom that sometimes accompanies serotonin syndrome. [9] You may notice that you are sweating more intensely than you normally would. This may happen even in a well-ventilated place without any heat source powerful enough to induce sweating.
Shivering
Shivering is also commonly associated with having abnormally high levels of serotonin in the body. [10] People who experience this symptom shiver in about the same way they would if they had a cold. You may experience this symptom even when you are not in a cold environment.
Seizures
A seizure is similar to a temporary blackout in the brain caused by a malfunction of electrical impulses and signals in the brain. In severe cases of serotonin syndrome, you may experience seizures. This is not a common symptom of abnormally high serotonin levels. It usually happens in severe cases of serotonin syndrome and can be life-threatening. If this happens to you or a loved one, it should be treated as a medical emergency.