Hi,
Well, dehydration (extreme or not) shouldn't be considered 'normal' at any time of the month, but it can happen if you're not replacing your fluids (especially water) daily. When you become dehydrated, your heart has to work harder to pump blood throughout your body, which increases your risk of high blood pressure and heart attacks. The most common signs of dehydration are: dizziness, dry mouth/ thirst, dark urine and urinating less, headaches, fatigue, and sometimes nausea. Sip water throughout the day, or try to drink 64 oz. of water a day (that breaks down to 8 oz./ 1 cup per hour for 8 hours), to help replenish and stay hydrated. Good Luck :)