From the
ADA website.
Normally, when your blood sugar level starts to drop, your liver steps in. It goes to work changing stored carbohydrate into glucose. Then it sends the glucose out into the blood, which helps you avoid or slow down a low blood sugar reaction.
However, when alcohol enters your system, this changes. Alcohol is a toxin. Your body reacts to alcohol like a poison. The liver wants to clear it from the blood quickly. In fact, the liver won't put out glucose again until it has taken care of the alcohol. If your blood glucose level is falling, you can quickly wind up with very low blood sugar.