CPR First Aid

What Happens to Your Blood Pressure When You are Dehydrated?

What Happens to Your Blood Pressure When You are Dehydrated

What if I told you your blood pressure is affected when you suffer from dehydration? The majority of people are aware of how important sufficient hydration is for health. After working out or in hot weather, people drink water. However, your body requires a lot of fluids in certain circumstances to avoid dehydration. One must be aware of these situations and familiarized with the possible effects of dehydration on blood pressure. This blog will teach you about what happens to your blood pressure when you are dehydrated, and how to manage blood pressure when dehydration happens.

What is Blood Pressure?

According to Mayo Clinic, Blood pressure monitors how strongly your blood pushes against your arteries as it circulates throughout your body. Your blood pressure can fluctuate between high and low depending on the type of activity you are engaging in.

Mayo Clinic: Blood pressure monitors circulatory strength; activity affects fluctuations.

What is Hypertension?

High blood pressure, often known as hypertension, is characterized by blood pressure that is higher than usual. This occurs when the push of your blood on the walls of your blood vessels is constantly too intense. High blood pressure harms the heart by making it function harder and less efficiently. The guidelines used to measure high blood pressure varies from healthcare professionals.

What is Hypotension?

Hypotension is another word for low blood pressure. Most doctors say your blood pressure is low if it is less than 90/60 mmHg. It is called “90 over 60” by your doctor.

What Do Blood Pressure Numbers Mean?

According to CDC, blood pressure is measured using two numbers:

  • The first number shows how much pressure is in your arteries when your heart beats. It is called systolic blood pressure.
  • The diastolic blood pressure number tells you how much pressure is in your arteries when your heart is at rest between beats.

What are the Causes of Hypertension and Hypotension?

There are different causes why a person acquires hypertension and hypotension. Hypertension has varied causes depending if it is primary or secondary hypertension. This is the same case with hypotension. It depends on your body position or your underlying medical health concern.

The Connection Between Blood Pressure and Dehydration

There is a significant effect on blood pressure when we are dehydrated. Dehydration can cause your blood volume to decrease. If you’re dehydrated, your blood volume and blood pressure can drop too low. This can prevent your tissues and organs from getting the oxygen and nutrients needed to stay healthy.

In extreme circumstances, your blood pressure could fall so low that your body experiences shock. When your organs aren’t getting enough oxygen, you could go into shock, a potentially fatal condition. One of the leading causes of shock is low blood volume from dehydration. The brain, kidneys, liver, and other organs stop functioning correctly without oxygen. Low blood pressure can permanently harm organs, tissues, and cells if left untreated.

When your body is dehydrated, it releases higher amounts of a chemical called vasopressin. Vasopressin helps your kidneys retain water, preventing you from losing more water through urination. At the same time, it causes your blood vessels to constrict, which then causes your blood pressure to increase. When this situation persists, you can develop high blood pressure.

Causes of Dehydration

There are many reasons why your body becomes dehydrated. It can occur when you are sick and have diarrhoea or are vomiting. Your body loses electrolytes before it can absorb essential fluids in the intestines. Physical activity in hot areas can also make you lose fluid and electrolytes. 

Dangers of Dehydration

According to Mayo Clinic, anyone can become dehydrated, but certain people are at greater risk:

  • Infants and children. Infants and children are most likely to have severe diarrhoea and vomiting and are more likely to become dehydrated. Since they have more surface area than volume, they lose more fluids when they have a high fever or get burned. Young kids can’t always tell you they’re thirsty or get themselves a drink.
  • Older adults. As you get older, your body’s fluid reserve shrinks, your ability to save water worsens, and your ability to feel thirsty gets dulled. Chronic diseases like diabetes and dementia, as well as the use of some medicines, make these problems even worse. Older people may also have mobility issues that make it hard to get water.
  • People with chronic illnesses. If you don’t control or treat your diabetes, you are at a high risk of becoming dehydrated. Kidney disease and medicines that make you urinate more also raise your risk. Even a cold or sore throat can make you more likely to get dehydrated because you don’t want to eat or drink as much when you’re sick.
  • People who work or exercise outside. When it’s hot and humid, you’re more likely to get dehydrated or ill from the heat. When the air is humid, sweat can’t evaporate as quickly and cool you off as it usually does. It makes your body temperature rise and makes you need more fluids.

Mayo Clinic: Dehydration risk varies.


Dehydration can lead to severe complications, including:

  • Heat injury. Suppose you need to drink more fluids while exercising vigorously and sweating heavily. In that case, you could get a heat injury, which could be anything from mild heat cramps to heat exhaustion or even heatstroke, which could kill you.
  • Urinary and kidney problems. If you are dehydrated for a long time, or if it happens more than once, you could get an infection in your urinary tract, kidney stones, or even kidney failure.
  • Seizures. Electrolytes — such as potassium and sodium — help send electric signals from one cell to another. If your electrolytes aren’t balanced, your body’s normal electrical messages can get messed up. This can cause your muscles to contract on their own and sometimes cause you to lose consciousness.
  • Low blood volume shock (hypovolemic shock). This is one of the worst things that can happen when someone is dehydrated and it can even be life-threatening. It occurs when your body gets less oxygen, and your blood pressure drops because you don’t have enough blood.

First Aid for Dehydration

Individuals with mild to moderate dehydration due to diarrhoea, vomiting, or fever can be better by consuming more water, fluids, vegetables and fruits.

First aid for cases of extreme dehydration should focus on stabilizing the patient and securing prompt medical attention.

Call 000 right away if you notice any severe dehydration-related symptoms. They will give medical advice and assist in getting the patient to the hospital so they can get the treatment they need. Most severe dehydration treatment strategies include intravenous (IV) therapy to replenish lost fluids and electrolytes.

Mild dehydration: drink fluids. Severe cases: seek medical help immediately. Call 000 for emergencies.

First Aid Courses for Dehydration in Liverpool

Risks of dehydration, hypertension and hypotension can be prevented. Early detection of signs and symptoms will help you manage it. If you are interested in enrolling in a first aid course in Liverpool, contact CPR First Aid for more information.

CPR First aid courses and training are open to all since emergencies such as complications caused by dehydration can happen to all ages, anywhere in Australia. NRT LogoHLTAID010 Provide an emergency first aid response is one of our popular courses. Contact us anytime for your queries.


Dehydration can significantly affect blood pressure. One of the best ways to avoid hypertension, low blood pressure and organ damage is to prevent dehydration. This can be managed at home for mild to moderate cases. However, someone severely dehydrated must immediately seek medical attention and dial 000. Being aware of the early warning signs and symptoms can save your life. Dehydration should be adequately managed early on to avoid problems and even death. Learn more by joining us by enrolling in a  first aid course in Liverpool; contact CPR First Aid for more information.

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