Before the ethanol in alcoholic beverages can start affecting the operation of your body, it must find its way into the bloodstream. Unlike the nutrients in food, ethanol is absorbed directly into the bloodstream, without being digested. About 20% of the alcohol is absorbed by the stomach, and 75% is absorbed through the walls of the small intestine. A small amount is absorbed directly through the mouth and throat, and a small amount is not absorbed, and passed out of the body with waste water.

Now that the ethanol has been absorbed directly into the bloodstream, it disperses itself throughout the bloodstream. Imagine a pool full of water and a bucket full of red ink. If you dump the ink into the pool, it will eventually turn a pinkish color as the ink distributes itself evenly. Now, the veins and arteries and capillaries in your body form a complete circle in and out of the heart, and all your muscles and organs are connected to the bloodstream and use that blood to do their tasks. So as soon as you drink one drink, the ethyl alcohol starts seeping through your stomach and small intestine and into your bloodstream, then visiting every organ in your body by way of that bloodstream.

Ethyl alcohol has different effects on different organs. The most immediate effect of the consumption of alcohol is its effect on the brain. But, like any drug, the effect of ethanol depends on its concentration in the bloodstream. There is an established way of representing the concentration of alcohol in the blood, which is the topic of the next section.