dry mucous membranes
skin tenting
sunken eyes
excessive thirst
headache
dizziness
altered mental status
weakness
fatigue
dark urine or decreased urine output
syncope
hemodynamic instability
Dehydration
Emotional or psychiatric causes
Diabetic ketoacidosis 
Pain, anger, or anxiety
Diabetic ketoacidosis
Response to fever 
Syndrome of inappropriate antidiuretic hormone secretion
SIRS 