Dehydration can cause uncomfortable symptoms.
Patients with a certain medical problems or on certain medications can get serious ill if dehydration occurs. This is an imprecise signal for dehydration. If often fails to kick in until the body is approaching a danger point People who sweat heavily are especially at risk, and are least likely to drink enough. Older people who are physically active are also at greater than average risk. Thirst sensation, sweat production and ability to concentrate urine decline with age.