Answer: Drink four (4) glasses of water one (1) hour before your exam. Do not empty your bladder. A full bladder helps the sonographer view the pelvic organs. Note: The water should be taken gradually to prevent abdominal discomfort.

In rare cases, drinking an extreme amount in a short time can be dangerous. It can cause the level of salt, or sodium, in your blood to drop too low. That's a condition called hyponatremia. It's very serious, and can be fatal. You may hear it called water intoxication.

Another report shows the development of hyponatremia with water intake of 2.5-5.6 gallons, or 10-20 liters, in just a few hours (5). A case of water intoxication and prolonged hyponatremia also occurred in a healthy, 22-year-old male prisoner after he drank 1.5 gallons (6 liters) of water in 3 hours (1).

“ Drinking too much fluid can lead to hyponatremia, which is when sodium in blood becomes too diluted,” Sims says. Symptoms include confusion, headaches, nausea and bloating—stuff that's easily confused with dehydration. In severe cases, hyponatremia can lead to seizures, organ failure and even death.

There are many different opinions on how much water we should be drinking every day. The health authorities commonly recommend eight 8-ounce glasses, which equals about 2 liters, or half a gallon. This is called the 8×8 rule and is very easy to remember.

“ It depends on your size and weight, and also on your activity level and where you live,” Nessler says. “ In general, you should try to drink between half an ounce and an ounce of water for each pound you weigh, every day.” For example, if you weigh 150 pounds, that would be 75 to 150 ounces of water a day.

We're constantly losing water from our bodies, primarily via urine and sweat. There are many different opinions on how much water we should be drinking every day. The health authorities commonly recommend eight 8-ounce glasses, which equals about 2 liters, or half a gallon.

Here's what happens to your body when you don't drink enough water. ... Any deficit in normal body water – through dehydration, sickness, exercise or heat stress – can make us feel rotten. First we feel thirsty and fatigued, and may develop a mild headache.