Alcohol has a diuretic effect. This means that it stimulates the body to produce more urine, which in turn can lead to dehydration. For every 1g of alcohol consumed, urine excretion increases by 10ml.(1) Long-term, habitual consumption of alcoholic beverages makes individuals less sensitive to thirst, so that by the time they feel thirsty, they are already more dehydrated than normal.(2)
For those who regularly consume alcohol, the body can compensate for the diuretic effect to some extent. For example, although urine output during the first three hours after consumption of alcohol increases, this is followed, six hours later, by an antidiuretic phase, during which more water is retained by the body.(3,4) Consuming alcoholic drinks after exercise delays rehydration, but the adverse effect is most significant with drinks containing 4 per cent or more alcohol.(5)
Drinking alcohol in moderation is not harmful, but problems can occur if alcohol is consumed in excess of up to 2 to 3 units of alcohol a day for women and 3 to 4 units a day for men. (A unit is half a pint of standard strength beer, lager or cider, or a pub measure of spirit. A glass of wine is about 2 units.)(6)
Alcohol is also high in calories and heavy drinking can lead to a wide range of health problems, including cancer, liver disease, stroke, high blood pressure and can affect mental health. In order to counteract the dehydrating effect of alcohol, you should have plenty of other non-alcoholic drinks that are not diuretics, such as water.(5)
• Don’t start drinking alcohol if you are thirsty – quench your thirst with water or a non-alcoholic drink first
• Avoid salty snacks such as crisps and nuts because these make you thirstier
• Drink water or non-alcoholic drinks throughout the evening
• Always have a glass or bottle of water with you as well as your alcoholic drink
• Think about the strength of your drink – choose beers or lagers that contain less alcohol and are less dehydrating.
• If you are susceptible to a hangover, try drinking a glass of water before going to bed and when you get up, then have another glass every hour during the day.
Last updated: December 2006
(1) Eggleton MG. The diuretic action of alcohol in man. J Physiol 1942;101:172-191
(2) Eisenhofer G, Johnson RH. Effects of ethanol ingestion on thirst and fluid consumption in humans. American Journal of Physiology 1983;244:R568-72
(3) Taivainen H, Laitinen K, Tahtela R, Kilanmaa K, Valimaki MJ. Role of plasma vasopressin in changes of water balance accompanying acute alcohol intoxication. Alcoholism: Clinical & Experimental Research 1995;19:759-62
(4) as reported in Stookey JD. The diuretic effects of alcohol and caffeine and total water intake misclassification. European Journal of Epidemiology 1999;15:181-88
(5) Shirreffs SM, Maughan RJ. Restoration of fluid balance after exercise-induced dehydration: effects of alcohol consumption. J Appl Physiol. 1997;83:1152-1158
(6) Food Standards Agency, Eat well, be well - Alcohol Accessed 30/06/06
