I've been doing some more checking because apparently I'm going to have drive home the point again with my friend. She still isn't drinking water and her heart rate is back up again. During dehydration, your body tries to protect your body's organs. It takes most of the available water from your blood and diverts it to your vital organs. The result is your blood is thicker and more difficult to pump. Thus, your heart beats faster. The longer this condition goes on the greater the chance of developing additional health problems that virtually can affect any area of the body. Rule of thumb for drinking water: each day drink about half your body's weight in ounces of water. Example: If you weigh 150 pounds, that means you would drink approximately 75 ounces of water or 2 1/2 qts or about 7 twelve-ounce glasses of water. That amount is assuming you are inside all day not exerting yourself much. Obviously you have to drink more if you are active. My other rule of thumb is the pee test: your urine should be light amber or clear as opposed to yellow. My favorite motto: if your pee's clear, you're clear!