Medical Q&As

Thirst - excessive?

I am concerned about a friend who is constantly thirsty. She drinks 7 to 8 litres of water a day. She has a healthy appetite and is very fit. She is approx. 5 foot 7 and approx. 8 stone. Any possible causes for this?

Most people do not drink enough water everyday however, 8 litres per day appears to be excessive. You say that your friend is very fit, which makes me question if she exercises a great deal which could give rise to profuse sweating, which in turn could generate thirst. Salty and spicy food can also make people thirsty as can certain medications including certain antidepressants, tranquillisers and diuretics, which are often colloquially referred to as water tablets. Recent onset of thirst raises the possibility that the person is suffering from diabetes mellitus. However, this is usually accompanied by increased eating and the paradoxical effect of losing weight. There is a less common form of diabetes known as diabetes insipidus, which is not an insulin related disorder. Despite the similarity in names diabetes insipidus refers to a completely unrelated condition that results in impaired regulation of water balance and this can also present with excessive thirst. Finally excessive drinking can be a symptom of psychological disturbance and may require the attention of a mental health professional.