According to WebMD, a person should not drink alcohol while taking lithium. The lithium can mask the effects of alcohol intoxication, making it more difficult to regulate the amount of alcohol ingested. This can lead to dangerously high blood alcohol levels.
When taking lithium, it is also important to avoid becoming overheated or dehydrated, especially in hot weather or while exercising. Drugs.com recommends drinking extra fluids while taking lithium. However, it is important to be careful not to drink an excessive amount of fluids as this can also be dangerous. The best course is to follow a doctor's instructions on the amount and type of fluids to drink.