Only between 2 and 10 percent of ingested alcohol exit the body through the kidneys, lungs and skin. Up to 5 percent is excreted by the kidneys and then eliminated through urine. Up to 5 percent is exhaled by the lungs, and a tiny percentage is excreted through sweat.
Alcohol is absorbed into the bloodstream through the stomach and intestines. The majority of absorbed alcohol undergoes metabolic processes, mainly in the liver. The liver chemically breaks down most of the alcohol. The small percentage of alcohol that remains unmetabolized is the blood alcohol concentration that can be detected in the urine and the breath.