Search IconSearch

The Link Between Dehydration and Blood Pressure

Not drinking enough fluids can send your blood pressure on a rollercoaster ride

Someone feeling light-headed, seeing birds and stars

The importance of maintaining a healthy blood pressure gets a lot of attention — and rightfully so. It’s key to keeping blood flowing so it can deliver oxygen and nutrients to every nook and cranny in your body.


Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy

The good news? There’s something simple you can do to assist the process and keep your blood pressure stable: Drink plenty of fluids.

Being dehydrated can cause your blood pressure to plummet and then potentially skyrocket in response. In extreme cases, this wild fluctuation could send you into a life-threatening case of shock.

So, how can dehydration increase your risk of experiencing both low blood pressure and high blood pressure? Preventive cardiologist Luke Laffin, MD, explains.

How dehydration causes low blood pressure

Approximately 55% to 60% of your body is made of water. There’s water in your bones, water in your muscles and water in your brain. Basically, there’s a splash of H2O everywhere inside of you.

Not surprisingly, your blood is mostly water — which explains why it flows through your veins like a liquid and drips when you get a cut. There are usually about 5 quarts (1.25 gallons) of blood in your system.

Now, let’s talk about dehydration.

When you’re dehydrated, it means that your body’s water supply is depleted. This can happen for any number of reasons, ranging from sweating a lot on a hot day, to medications or simply not drinking enough.

Whatever the cause, that loss of fluid is felt everywhere in your body — including blood volume. Low blood volume leads to low blood pressure, meaning your organs may not get the oxygen needed to function properly.

“In the simplest of explanations, you’re just not filling up the pipes enough for what your vascular system needs,” says Dr. Laffin.

In the most extreme cases, this drop can cause heart or brain damage or even death.

Signs of low blood pressure

Concerning symptoms of low blood pressure may include:


How dehydration causes high blood pressure

Your body has mechanisms in place to counteract when blood pressure drops to lower-than-optimal levels. That’s a good thing … unless the correction turns into an overcorrection, notes Dr. Laffin.

When you’re dehydrated, sodium levels in your blood typically rise. Your system responds by releasing more of a hormone called vasopressin, which works to help your body hang on to water.

Vasopressin also can cause your blood vessels to tighten, or constrict, which makes your blood pressure rise. (This becomes more of a concern if you’re already dealing with hypertension, or chronically high blood pressure.)

Best advice? Stay hydrated

Want to avoid blood pressure issues related to hydration? Then, just make sure you’re drinking enough fluids during the day.

As a general guideline, the National Academies of Science, Engineering and Medicine recommends consuming 125 ounces (3.7 liters) of fluid per day for men and 91 ounces (2.7 liters) for women.

But your fluid intake needs may be greater, depending on factors such as weather, location and physical activity. Taking certain medications also may make you more prone to dehydration.

“Staying hydrated helps to keep your body in balance in many ways, including your blood pressure,” says Dr. Laffin. “Understanding that and being consistent about fluid intake can help keep you out of trouble.”


Learn more about our editorial process.

Related Articles

Lifeguard looking at water with binoculars while two kids fly kites on the beach
May 23, 2024/Primary Care
12 Summer Health Risks To Watch Out For

From bug bites and blisters to sunstroke and swimming safety, here’s how to stay well this season

Person drinking from a coffee mug
May 21, 2024/Nutrition
Grounded in Reality: Does Coffee Dehydrate You?

Coffee is made up of mostly water, but it’s the caffeine you have to look out for

Man sitting down at beach workout area with head in hand, eye closed
April 8, 2024/Primary Care
Why Does the Sun Make You Tired? Here Are 7 Reasons

Your body works overtime to keep you cool on hot summer days, bringing on sun fatigue

Person reclining on couch wearing compression socks
April 3, 2024/Heart Health
How To Raise Your Blood Pressure Immediately at Home

First things first — slowly sit or lie down

person running with food and fitness images floating behind
March 6, 2024/Exercise & Fitness
Is It Safe to Work Out While You’re Fasting?

It’s best to exercise before or after your fast, instead of during it

two kids eating snow outside
March 6, 2024/Nutrition
Is It Safe To Eat Snow?

If the flakes are undisturbed, pristine white and come from the top layer, it’s typically safe to indulge in a scoop

person standing in front of taped off refrigerator thinking about food and watching the time
March 5, 2024/Nutrition
6 Tips for Fasting Safely

Plan ahead by hydrating, cutting back on sugar and managing medications

A wooden spoonful of salt on a granite tabletop with salt scattered around
February 28, 2024/Nutrition
Why Too Much Salt Can Be Bad for You

Excess salt and sodium consumption is a worldwide health concern

Trending Topics

Female and friend jogging outside
How To Increase Your Metabolism for Weight Loss

Focus on your body’s metabolic set point by eating healthy foods, making exercise a part of your routine and reducing stress

stovetop with stainless steel cookware and glassware
5 Ways Forever Chemicals (PFAS) May Affect Your Health

PFAS chemicals may make life easier — but they aren’t always so easy on the human body

jar of rice water and brush, with rice scattered around table
Could Rice Water Be the Secret To Healthier Hair?

While there’s little risk in trying this hair care treatment, there isn’t much science to back up the claims