This article is intended for general informational purposes only and is not a substitute for professional medical advice, diagnosis or treatment. Fluid needs vary with age, health, climate and activity level. These symptoms can have many causes, so do not assume dehydration is the reason. People with heart, kidney or other medical conditions, or those on fluid restrictions, should consult a doctor before changing their water intake. Seek medical help promptly if you experience severe dizziness, confusion, a rapid heartbeat, fainting or very little urine.