Decreased urine output
Sunken fontanelle
Most reliable: 
Abnormal capillary refill
Abnormal respiratory pattern
Decreased skin turgor
Abnormal capillary refill
Abnormal respiratory pattern
Decreased skin turgor
Dehydration 
Diabetic ketoacidosis 
Diabetic ketoacidosis
Syndrome of inappropriate antidiuretic hormone secretion
Starvation ketoacidosis
Cerebral edema in DKA
Hyperosmolar hyperglycemic state
Dialysis-associated hypotension