In "Stranger Things," Eleven often gets a nosebleed after using her powers.
The symptom is most closely associated with her telekinetic and psychic abilities. When Eleven pushes her powers hard—such as moving objects, attacking enemies, opening dimensional Gates, or reaching people through remote viewing—she can become physically weakened and begin bleeding from her nose.
The nosebleed is not a separate superpower or a random recurring injury. It visually signals the physical cost of her abilities and shows viewers that using them requires intense concentration and exertion. In several scenes, the severity of the bleeding reflects how much power Eleven is using.
Eleven, whose birth name is Jane Ives, was taken from her mother and raised as a test subject at Hawkins National Laboratory under Dr. Martin Brenner. The laboratory's experiments were designed to develop and exploit her psychokinetic and extrasensory abilities. Her powers also allow her to interact with the Upside Down, a parallel dimension central to the series. A headache can accompany exhaustion, but the signature symptom is the nosebleed.