Dehydration can cause your blood pressure to change. A drop in blood volume can lead to a potentially dangerous drop in blood pressure and even shock. High blood pressure has also been linked to dehydration.

Dehydration happens when your body doesn’t have enough fluids. Not drinking enough fluids or losing fluids faster than you can replace them can both result in dehydration.

Dehydration can be serious. If it’s left untreated, it can lead to life threatening complications, like heat-related emergencies and kidney problems.

Additionally, dehydration can cause potentially dangerous changes in blood pressure.

Continue reading to learn more about dehydration, its effect on blood pressure, and the symptoms to watch out for.

Blood pressure is the force your blood exerts on the walls of your arteries and veins. Dehydration can affect your blood pressure, causing it to spike up or go down. Let’s take a closer look at why this happens.

Low blood pressure is when your blood pressure reading is lower than 90/60 mm Hg. Dehydration can cause low blood pressure due to a decrease in blood volume.

Blood volume is the amount of fluid that’s circulating in your blood vessels. Maintaining a normal blood volume is necessary for blood to be able to adequately reach all of the tissues of your body.

When you’re very dehydrated, your blood volume can decrease, leading to a drop in blood pressure.

When blood pressure drops too low, your organs won’t receive the oxygen and nutrients they need. You could potentially go into shock.

High blood pressure is when you have a systolic (top number) reading of 140 mm Hg or higher, or a diastolic (bottom number) reading of 90 mm Hg or higher.

Dehydration has been linked to high blood pressure. However, research into this topic is limited. Additional work is needed to investigate the connection.

Although more research is needed, it’s still worth noting that dehydration can lead to an increase in blood pressure due to the action of a hormone called vasopressin.

Vasopressin is secreted when there’s a high amount of solutes (or sodium level) in your blood, or when your blood volume is low. Both of these things can happen when you lose too much fluid.

In response, when you’re dehydrated, your kidneys reabsorb water as opposed to passing it in urine. High concentrations of vasopressin can also cause your blood vessels to constrict. This can lead to an increase in blood pressure.

In addition to changes in blood pressure, there are other dehydration symptoms to look out for.

Oftentimes, you’ll feel these symptoms before you know that you’ve had a change in blood pressure. These symptoms include:

Additionally, children who are dehydrated may have the following symptoms:

  • no wet diapers for several hours
  • absence of tears when crying
  • irritability
  • sunken cheeks, eyes, or soft spot on the skull (fontanel)
  • listlessness

Other than not drinking enough fluids, there are other possible causes of dehydration. They can include:

  • Illness. A high fever can lead to dehydration. Additionally, vomiting and diarrhea can lead to a significant loss of fluids and electrolytes.
  • Increased sweating. Water is lost when you sweat. An increase in sweating can occur in hot weather, during exercise, and if you’re sick with a fever.
  • Frequent urination. You can also lose fluids through urination. Medications like diuretics, underlying conditions such as diabetes, and alcohol consumption can all cause more frequent urination.

It’s important to seek prompt medical attention if you have any of the following symptoms:

  • diarrhea that’s lasted longer than 24 hours
  • inability to keep fluids down
  • a rapid heartbeat
  • extreme exhaustion, disorientation, or confusion
  • stool that’s black or bloody

For low blood pressure

A lower than normal blood pressure reading, without other symptoms, may not be a cause for concern.

However, if you have low blood pressure readings along with other symptoms, it’s important to get medical care.

Symptoms to look out for include:

  • feelings of lightheadedness or dizziness
  • nausea
  • feeling tired or fatigued
  • blurry vision

Shock is a medical emergency that needs immediate care. Dial 911 if you have lower than usual blood pressure and symptoms like:

For high blood pressure

High blood pressure doesn’t usually cause symptoms. Most people find out about it during a routine checkup with their doctor.

If you regularly take your blood pressure and find that your readings are consistently high, see your doctor.

The key to preventing dehydration is to make sure you take in enough fluid each day. But how much water or other fluids should you drink in a day?

Daily fluid recommendations can depend on several factors, including things like:

  • age
  • sex
  • weight
  • your overall health
  • weather conditions
  • activity level
  • pregnancy or breastfeeding

According to the Mayo Clinic, a good goal to aim for is to drink at least eight glasses of water a day.

If you find it hard to drink plain water, you can also stay hydrated by drinking:

  • water infused with slices of fruit, like lemon or cucumber
  • sugar-free sparkling water
  • smoothies made with fruits and vegetables
  • decaffeinated herbal tea
  • milk
  • low sodium soups

Also remember that you can get water from some food sources, particularly fruits and vegetables.

Additionally, follow the tips below to help yourself stay hydrated:

  • Always drink when you feel thirsty. Feeling thirsty is your body’s way of telling you that you need more fluids.
  • Remember to drink more water when you’re being physically active, in a hot climate, or ill with a fever, vomiting, or diarrhea.
  • Carry a water bottle with you as you go about your daily activities. That way you’ll always have water on hand.
  • Choose water instead of sugary sodas, energy drinks, sweetened beverages, or alcoholic drinks.

Changes in blood pressure can occur due to dehydration.

A drop in blood volume can lead to a potentially dangerous drop in blood pressure and even shock.

High blood pressure has also been linked to dehydration. More research is needed to fully understand the connection.

You can prevent dehydration by drinking plenty of fluids. This is especially important if you’re ill, in a warm environment, or being physically active.