Can Dehydration Cause High Blood Pressure? Doctors Share How to Keep Your BP Balanced Naturally
Feeling dizzy or lightheaded? Learn how fluid intake affects your blood pressure
Proper hydration is essential for keeping cells, tissues and organs functioning optimally. “Remember, we are mostly made of water, and so keeping up our water stores is crucial,” says Mohanakrishnan Sathyamoorthy, MD, FACC, chair of internal medicine at Texas Christian University’s Burnett School of Medicine. If you’re not getting enough fluids throughout the day, you may start to experience common symptoms of dehydration, including headaches, dizziness and tiredness. But can dehydration cause high blood pressure too? Read on to find out.
What is a normal blood pressure reading?
Blood pressure is the force of blood pushing against the walls of your arteries. This is expressed as two numbers, measured in millimeters of mercury (mmHg). The top number, or systolic pressure, measures the force against your arteries as blood pumps away from the heart. The bottom number, or diastolic pressure, measures the force against your arteries as blood returns to the heart in between heartbeats.
According to the American Heart Association, a systolic reading between 90 and 120 mmHg and a diastolic reading between 60 and 80 mm Hg is considered normal. When blood pressure levels are within the normal range, it means your heart is able to pump blood efficiently, carrying oxygen and nutrients throughout your body.
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High blood pressure (hypertension) is diagnosed when your readings are 130/80 mmHg or higher. High blood pressure can damage the arteries over time and make your heart work harder to pump blood, hampering your overall health.
Low blood pressure can be a problem, too
Low blood pressure (hypotension) is defined by the National Heart, Lung and Blood Institute as a reading below 90/60 mmHg. It isn’t always harmful, but a sudden drop in blood pressure can potentially lead to reduced oxygen delivery to the body’s tissues and organs.
“When you have low blood pressure, it means there’s less force pushing oxygenated blood through the bloodstream, and organs might not receive enough oxygen to function properly,” says Raj Dasgupta, MD, board-certified physician specializing in internal medicine and critical care and Chief Medical Advisor for Sleepopolis. “That can lead to fainting, falls or in serious cases, shock, which is a medical emergency.” According to the Mayo Clinic, even a drop of 20 mmHg is enough to cause dizziness or lightheadedness.
Can dehydration cause high blood pressure?
Hydration plays a key role in supporting blood flow. “Staying hydrated keeps your blood volume where it needs to be, which helps your heart pump efficiently and keeps your blood pressure steady,” Dr. Dasgupta says.
When you’re dehydrated, blood volume is reduced, which can cause an initial drop in blood pressure. Symptoms of low blood pressure may include dizziness, nausea, headache, blurry vision, fatigue, heart palpitations, lightheadedness or fainting.
When this happens, Dr. Dasgupta says, “The body responds by increasing blood pressure in an attempt to compensate.” Your heart may beat faster, and your body may release hormones to help constrict the blood vessels. Blood pressure typically returns to normal once fluids have been replenished, he adds.
But if you find you often aren’t drinking enough water, chronic dehydration can lead to high blood pressure. “Chronic dehydration will eventually activate neurohormonal, endocrine and renal pathways that can lead to rises in blood pressure to maintain what we call central organ perfusion—that is, to keep enough blood flow to our organs,” Dr. Sathyamoorthy explains.
Risk factors for dehydration and high blood pressure
A few things can increase your odds of experiencing these changes in blood pressure:
- Hypertension. “People with high blood pressure are used to having a higher baseline, so a sudden drop—even to what’s technically a ‘normal’ level—can feel pretty rough and bring on symptoms like dizziness or fainting,” Dr. Dasgupta says.
- Hot weather. Exposure to excessive heat increases your risk of dehydration, Dr. Sathyamoorthy says. Be sure to monitor your fluid intake during summer weather, especially when exercising or engaging in other physical activity.
- Illnesses. Infections, fevers, vomiting or diarrhea can all increase your chances of becoming dehydrated, Dr. Sathyamoorthy says.
- Underlying conditions. You may be more likely to experience fluctuations in blood pressure, or more sensitive to symptoms of low blood pressure, if you take blood pressure medication or have certain heart or nerve conditions, Dr. Dasgupta says.
How to prevent dehydration-triggered blood pressure swings
There are a few simple steps you can take to help prevent high or low blood pressure caused by dehydration. Here’s what works:
Drink up
The best strategy to prevent high blood pressure is to avoid getting dehydrated in the first place. So, how much water do you actually need to drink each day? According to the Academy of Nutrition and Dietetics, women should aim for 11.5 cups of fluid per day. Around 20 percent of that will come from water-rich foods, so around eight or nine cups should come from water, tea and other beverages.
To hit that goal, Dr. Dasgupta recommends carrying a refillable water bottle and sipping throughout the day—don’t just wait until you’re parched. Hydrating foods like watermelon or cucumbers can also boost your fluid intake, he adds.
Squeeze in more exercise
Aim for at least 30 minutes a day, which you can break up into smaller chunks. Exercise helps manage blood pressure, which may make you less susceptible to fluctuations. “Exercise temporarily bumps up your blood pressure, but over time it helps lower your baseline,” Dr. Dasgupta says. According to research published in Advances in Experimental Medicine and Biology, cardio and strength training exercises have both been proven to reduce blood pressure.
Just be sure to hydrate before and after your workout, especially in hot weather. “If you’re sweating a lot, consider drinks with electrolytes,” Dr. Dasgupta says. “Electrolytes help balance your fluids and keep your muscles and nerves, including your heart, working properly. If they’re out of whack, you can feel weak, dizzy or have blood pressure swings.”
Don’t go overboard
Excessive water intake can lead to abnormally low sodium levels, especially if you chug a lot of water after an intense workout without addressing electrolyte loss. “As we say in exercise training, steady pace wins the race!” Dr. Sathyamoorthy adds. “Drink when you are thirsty, and maintain a steady intake of a mixture of fluids over the day with amounts determined by your size and medical conditions.” When in doubt, your doctor can help you figure out your hydration needs.
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