A method for monitoring user health, a device for monitoring user health, and a terminal for monitoring user health are provided. A method for monitoring user health includes: acquiring an illuminance of an environment, where the environment is an environment in which a user is currently located； acquiring a first pupil size when the user is located in the environment； correcting the first pupil size on the basis of the illuminance to acquire a second pupil size； comparing the second pupil size with a reference pupil size to determine a change rate of a pupil size of the user； and determining a health state of the user on the basis of the change rate of the pupil size.
