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Level of Consciousness

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Updated April 29, 2014

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

Definition:

Level of consciousness (LOC) is a medical term used to describe a patient's awareness of his or her surroundings and arousal potential. Level of consciousness can range from alert to coma. Some common descriptions of level of consciousness include:

  • Alert - the person is awake and aware of their surroundings.
  • Drowsy - the person is tired and may be dozing but can easily be aroused.
  • Lethargic - the person is sluggish and drowsy and has to work hard to focus on their surroundings.
  • Obtunded - the person is unconscious and only able to arouse with strong physical stimuli, such as loud noises or painful stimulation.
  • Coma - the person is unconscious and unable to be aroused.

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