If you have seen someone who has had too much to drink, you've probably noticed definite changes in that person's performance and behavior. The body responds to alcohol in stages, which correspond to an increase in BAC:
They become more self-confident or daring.
Their attention span shortens.
They may look flushed.
Their judgment is not as good - they may say the first thought that comes to mind, rather than an appropriate comment for the given situation.
They have trouble with fine movements, such as writing or signing their name.
(BAC = 0.03 to 0.12
They become sleepy.
They have trouble understanding or remembering things (even recent events).
They do not react to situations as quickly (if they spill a drink they may just stare at it).
Their body movements are uncoordinated.
They begin to lose their balance easily.
Their vision becomes blurry.
They may have trouble sensing things (hearing, tasting, feeling, etc.).
(BAC = 0.09 to 0.25
They are confused -- might not know where they are or what they are doing.
They are dizzy and may stagger.
They may be highly emotional -- aggressive, withdrawn or overly affectionate.
They cannot see clearly.
They are sleepy.
They have slurred speech.
They have uncoordinated movements (trouble catching an object thrown to them).
They may not feel pain as readily as a sober person.
(BAC = 0.18 to 0.30
They can barely move at all.
They cannot respond to stimuli.
They cannot stand or walk.
They may vomit.
They may lapse in and out of consciousness.
(BAC = 0.25 to 0.4 percent)
They are unconscious.
Their reflexes are depressed (i.e. their pupils do not respond appropriately to changes in light).
They feel cool (lower-than-normal body temperature).
Their breathing is slower and more shallow.
Their heart rate may slow.
They may die.
(BAC = 0.35 to 0.50 percent)
- (BAC more than 0.50 percent) - The person usually stops breathing and dies.