Dehydration does not cause high blood pressure. It usually causes blood pressure to drop. Dehydration occurs when your body lacks the water it needs to work normally. Causes include:

  • Not drinking enough water or fluids
  • Excessive sweating, such as while exercising or in a hot climate
  • Water loss from vomiting or diarrhea

Water makes up half of the body’s weight. Water is a major part of blood. Less fluid in the body means there is less blood in the blood vessels. This causes lower pressure. One of the first signs of low blood pressure is feeling dizzy when you stand up. Other symptoms include thirst and weakness. This can last until you replace the water you have lost.

If you think you are dehydrated especially if you are feeling dizzy when you stand up, take small sips of water and call your doctor.