Hydration status and cardiovascular health intertwine closely. Dehydration can lead to blood pressure changes, while some medications for high blood pressure may cause dehydration.

Dehydration can cause the heart to work harder to pump blood throughout the body. Taking medications for high blood pressure may lead to dehydration.

Water constitutes more than half of the adult body, and body fluid highly affects cardiovascular function.

Dehydration occurs when the body loses more fluid than a person takes in. Chronic dehydration complicates many medical conditions and is a frequent cause of hospital admissions.

High blood pressure (hypertension) happens when the force of blood against the blood vessel walls is consistently too high. Nearly 50 in 100 American adults have hypertension.

This article explores the link between hypertension and dehydration, their symptoms, and treatments.

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Water in the body distributes between two compartments: Intracellular water (ICW) and extracellular water (ECW). The electrolyte concentration of the water in a person’s body determines the movement of fluids from the two compartments.

Dehydration causes the body to release higher amounts of the chemical vasopressin, or antidiuretic hormone (ADH). This causes water retention in the kidneys, which helps prevent further water loss through urination.

However, vasopressin also causes blood vessel constriction and increases systemic vascular resistance, leading to an elevation of blood pressure.

Dehydration also causes the blood to retain more sodium. This thickens the blood and makes it harder for the blood to circulate through the body.

A 2022 study found a strong association between hydration parameters and hypertension status. People with hypertension have high ECW, possibly because of higher salt intake or due to compensations for chronic dehydration.

High blood pressure also links to dehydration, but the exact mechanism remains unknown to researchers.

Conversely, extreme dehydration may cause low blood volume, leading to a drop in blood pressure and hypovolemic shock.

Medication and dehydration

Angiotensin-converting enzyme (ACE) inhibitors and angiotensin II receptor blockers (ARBs) are drugs that doctors frequently prescribe for people with hypertension. One of the side effects of these drugs is dehydration.

The following are the most common symptoms of dehydration:

Hypertension typically develops over time and shows no warning signs or symptoms. However, those with very high blood pressure — 180/120 millimeters of mercury (mm Hg) or higher — can experience the following symptoms:

Doctors may ask people to replenish their fluids by drinking water. This does not raise blood pressure in younger people with healthy kidneys.

They may evaluate a person’s heart rate and blood pressure when lying, sitting, and standing (which health professionals call “orthostatic vital signs”). This is to assess dehydration requiring rapid fluid replacement through intravenous (IV) or oral fluids.

Treatment for high blood pressure involves adopting a heart-healthy lifestyle with or without medications. Doctors may recommend a person makes the following habit changes to control or lower high blood pressure:

  • eat heart-healthy foods
  • maintain regular physical activity
  • keep a healthy weight
  • avoid or limit alcohol
  • quit smoking
  • manage stress
  • get enough good quality sleep

A doctor may prescribe several blood pressure medications to manage a person’s high blood pressure. These can include:

Some of these medications can cause dehydration, so a doctor may also recommend a person drink plenty of fluids to replenish water loss.

Dehydration and hypertension are two conditions that can have profound health implications. Aside from this, the two conditions may directly affect one another.

Dehydration can lead to high blood pressure (hypertension) by constricting blood vessels, while many medications that doctors prescribe to treat hypertension may cause dehydration.

Because of this, those with hypertension must stay hydrated and maintain a healthy lifestyle to manage their high blood pressure.

Additionally, those taking medications for hypertension should drink plenty of fluids and regularly replenish their water intake to counter any potential dehydration side effects.