Symptoms of mild dehydration include:

• Decreased urination
• Urine is darker than usual

Symptoms of mild to moderate dehydration include:

• Decreased urination:
• No urination for over 8 hours
• Dizziness
• Dry mouth
• Dry skin
• Fainting
• Nausea
• Excessive thirst
• Weakness or fatigue
• Rapid pulse

Symptoms of severe dehydration include:

• Decreased urination:
• No urination for over 12 hours
• Low blood pressure
• Rapid pulse
• Confusion
• Lethargy:
• Excessive sleepiness
• Coma