Alcohol's impact on each person is somewhat unique, which is one reason why it's important to work with a professional when you are dealing with drunk driving charges. While the impact of alcohol might be slightly different in your system, some generalizations can be made about how your body changes as you reach various levels of blood alcohol content.
At 0.02 BAC, which some people can reach with very little alcohol in the system, the body might become slightly warm and more relaxed. This is within the legal limit for an adult, but not for a minor. Also within the legal limit for an adult in most areas is a BAC of 0.05, which can result in sedation-like effects and a reaction time that is slowed.
Once you cross into areas where you are over the legal limit, impacts are usually more severe. At 0.10 BAC, many people show labored or slow thinking, poor coordination, and slurred speech. At 0.20 BAC, it's common to have trouble walking and you might experience nausea, vomiting and double vision. If you are experiencing any of these effects of alcohol, you should not be driving.
By the time you reach 0.30 BAC, you might pass out, have temporary memory loss or experience blackouts or deal with tremors. At 0.40 BAC, your body has difficulty dealing with the amount of alcohol in your system. You could struggle to breathe and even die from the alcohol in your system.
Again, everyone's body reacts differently, and some people do not feel the impact of alcohol as quickly. It's possible to be above the legal limit without stumbling, slurring words or having trouble with thought processes, which is why you can't base your decision to drive on how you feel. If you have any drinks, you should avoid getting behind the wheel. If you are caught driving with a BAC above the legal limit, a conviction on DUI isn't automatic, though, and you might want to work with a professional to ensure your defense is strong.
Source: WebMD, "Blood Alcohol," accessed Sep. 30, 2016