Alcohol can affect blood sugar for several hours after drinking. Some drinks, especially beer or sweet mixed drinks, may raise blood sugar soon after drinking because they contain carbohydrates. Later, alcohol can lower blood sugar, especially when the liver is busy processing alcohol instead of releasing stored glucose.
This delayed drop is more likely in people with diabetes who use insulin or medicines that increase insulin release. It can also happen if alcohol is consumed without food, after exercise, or after heavy drinking. Some guidance notes that low blood sugar may occur many hours later, and in some cases up to about 16 hours after drinking stops.
The risk can be higher overnight because symptoms of low blood sugar may be missed during sleep. Eating a meal with alcohol, avoiding drinking on an empty stomach, and checking glucose more often can help reduce this risk.
People with diabetes should ask their doctor or diabetes care team how alcohol fits with their treatment plan. Do not change diabetes medication doses or use extra medication to “correct” alcohol-related sugar changes without medical guidance.