Dizziness or lightheadedness, especially when standing up
Fainting or near-fainting
Blurred or dim vision
Nausea
Fatigue or weakness
Trouble concentrating
Cold, clammy, or pale skin
Rapid, shallow breathing
Thirst
Unusual confusion
Feeling unsteady or off balance
A blood pressure reading below 90/60 mm Hg
Symptoms that worsen after standing, eating, or exertion