Can Dehydration Cause High Blood Pressure?

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You know water is important to your health. But did you know one of the benefits of drinking water is normal blood pressure?

The adult body is up to 60% water. Your heart contains up to 73% water and your blood is 90% water.

So, it’s no surprise water consumption is the “secret sauce” for maintaining normal blood pressure—yet it’s a risk factor many people overlook.

Why Dehydration Can Cause High Blood Pressure

Your blood pressure is made up of two numbers. Systolic pressure (top number) is the force on your artery walls when your heart contracts. Diastolic pressure (bottom number) is the pressure on your arteries between heartbeats. Healthy is below 120/80 mm Hg.

Dehydration can affect your blood pressure in several ways:

Narrowing Your Arteries

When you’re dehydrated, your brain stimulates the release of vasopressin, a hormone that narrows your arteries, raising your blood pressure.

Stimulating the Release of Renin

When you’re dehydrated, your kidney responds by releasing the enzyme renin. Renin’s job is to keep your blood pressure healthy by maintaining healthy levels of potassium and sodium in your body.

Renin works by stimulating a cascade of events in your body, much like a “domino effect.” It converts angiotensin in your body into angiotensin I, which is then converted into angiotensin II.

Angiotensin II is the final “domino.” It stimulates the release of aldosterone, a hormone that promotes the absorption of sodium by your kidneys. Aldosterone helps to regulate the balance of water and salt in your body, so you retain water—and also raises your blood pressure.

Renin is both a friend and a foe! It’s your body’s “water insurance mechanism” and can be extremely helpful if you suddenly become dehydrated, such as by sweating too much without drinking enough liquids. Yet, persistently high renin levels can cause high blood pressure.

Putting Pressure on Your “Pipes”

When you’re dehydrated, it forces your body to gradually and systematically close down some of its capillary bed. This puts more pressure on your capillaries and arteries (the “pipes”), raising your blood pressure.

What Are the Symptoms of Dehydration?

Don’t wait to feel thirsty before you drink water. Many people don’t realize it, but thirst is a sign that your body is already dehydrated. So, your goal is to drink enough fluids to avoid thirst.

Symptoms of dehydration can include:

  • A change in blood pressure
  • Fainting
  • Less frequent urination
  • Darker and smellier urine
  • Fatigue
  • Dizziness
  • Confusion
  • Dry mouth and lips
  • Irritability
  • Headaches
  • Cramping in the legs and arms

If you’re experiencing any of these symptoms, you want to think about how much water you’ve been drinking. If you’re not drinking enough, it can mean you’re dehydrated.

As You Age, You’re More Prone to Dehydration

Something I found in my clinical practice is that dehydration is far more common as people age. In fact, many of my patients had no idea they were dehydrated until I pointed it out.

One reason is that people lose their sense of thirst as they age, so your body is no longer reminding you to drink water. This is especially problematic when it’s hot and humid.

People can also miss the signs of dehydration as they age. So, you might have a dry mouth, dizziness, or muscle cramps and attribute it to something else, rather than dehydration.

Advancing age can also make people more prone to imbalances in their sodium and electrolyte levels. So, for my older patients, I always recommended sipping water throughout the day and not waiting for the sensation of thirst.

One trick to check for dehydration is to gently pinch the skin on your forearm. If it doesn’t spring back quickly, it can mean you’re dehydrated.

Can Drinking Water Help to Lower Blood Pressure?

If you’re not drinking enough water, it makes you far more likely to have high blood pressure. The remedy is drinking more water to help lower your blood pressure.

How much water should you drink? The goal is to drink enough water to avoid thirst. For healthy blood pressure and overall health, I recommend drinking eight to ten 8-ounce glasses of water per day.

Yet, be careful to not overdo it. While I want you to get the health benefits of drinking water, I don't want you to go overboard. Like a sponge, your body can absorb water at a limited rate. It will require some time to adapt to your new level of water intake and become fully hydrated.

It’s also important to drink more water when you exercise since you lose water through sweat and evaporation. So, to get the full benefits of drinking water you want to hydrate well before, during, and after exercise.

Does Water Retention Cause High Blood Pressure?

Not only can dehydration cause high blood pressure, but so can water retention which is sometimes referred to as “fluid overload.” One of the top culprits is salt retention.

When you have too much sodium in your body, your body holds onto water, which increases your blood volume and raises your blood pressure. Symptoms of water retention can include edema (swelling in your ankles and feet), bloating, puffiness, and persistent coughing.

There are many causes of fluid retention, including heart failure, cirrhosis of the liver, kidney failure, and more. But if your water retention is caused by too much sodium, the answer is to cut down on your salt consumption. Yet, you don’t want to cut down too much.

To maintain a healthy blood pressure level, you want to aim for 2.8 grams of sodium a day. Not only is it important to reduce your use of table salt, but you also want to watch how much sodium you’re getting in processed foods. Some of the worst culprits include crackers, pretzels, canned soups, and frozen meals.

The Bottom Line

Drinking water can help to lower your blood pressure and keep it in the normal range. Yet, drinking too much water can overwork your kidneys and digestive system. Hypertension, diabetes, and stress all leave the kidneys in a weakened state, so be careful.

Your salt intake is also extremely important. You want to eat about 2.8 grams of sodium daily, to avoid water retention and high blood pressure.

Finally, if you have congestive heart failure, kidney issues, or are taking diuretics and/or are on fluid restrictions, consult your physician before increasing your water intake. That’s because hypertension, diabetes, and stress all leave the kidneys in a weakened state.

Dr. Stephen Sinatra

Meet Dr. Stephen Sinatra

A true pioneer, Dr. Sinatra spent more than 40 years in clinical practice, including serving as an attending physician and chief of cardiology at Manchester Memorial Hospital, then going on to formulate his advanced line of heart health supplements. His integrative approach to heart health has changed the lives of hundreds of thousands.

More About Dr. Stephen Sinatra