What does alcohol do to your blood sugar and insulin sensitivity?

Alcohol on an empty stomach can cause your blood sugar to drop to dangerously low levels. The liver stops producing and releasing glucose, even though glucose is precisely what is needed to keep your blood sugar stable. This risk is greatest when your glycogen stores (the glucose reserves in the liver) are already depleted, or when you are taking blood-sugar-lowering medication such as sulfonylureas.

With a carbohydrate-rich meal, the opposite happens. The body prioritises alcohol as a fuel source, which temporarily slows the processing of carbohydrates. This can actually cause blood sugar to rise briefly, along with a corresponding insulin response. Blood sugar can then drop too far afterwards, especially if the meal contained fast-acting carbohydrates.

Moderate drinking is linked in studies to better insulin sensitivity and also to a slightly lower risk of type 2 diabetes. However, this is an association from observational research; whether it is causal has not been established. Excessive drinking reverses this picture entirely: it disrupts blood sugar regulation and cancels out any potential beneficial effects.

An interesting side note: a large Korean study shows that genetic predisposition also determines how your blood sugar responds to alcohol. Certain variants in a gene involved in protein breakdown appeared to be associated with lower fasting glucose levels in drinkers. This does not apply to everyone and cannot be broadly generalised. How alcohol affects you therefore also depends on your genetic background, although that is difficult to predict in practice.