- It is possible to lose fluid so quickly that the normal thirst mechanism is overwhelmed - we just don't 'feel' thirsty.
- The sources of fluid loss are breathing, sweating, urinating and defecating.
- The rate of loss from each of these will vary according to activity levels, air temperature, humidity and altitude.
- Exercise, sweating, diarrhea, temperature or altitude can significantly increase the amount of fluid required.
- The most common cause of increased fluid loss is exercise and sweating.