How Dehydration Affects Blood Pressure: The Key to Staying Hydrated for Heart Health

Maintaining a healthy blood pressure is essential for ensuring oxygen and nutrients are delivered throughout your body. Fortunately, there’s a simple yet effective way to support this process—staying hydrated.

Dehydration can lead to drastic fluctuations in blood pressure, first causing it to drop and then potentially spike as your body tries to compensate. In severe cases, these sudden changes can become life-threatening.

How Dehydration Leads to Low Blood Pressure

Since water makes up about 55% to 60% of the human body, it plays a key role in nearly every function—including blood circulation. Blood itself is largely composed of water, which allows it to flow smoothly through your veins.

When your body loses too much fluid, whether due to excessive sweating, medication side effects, or simply not drinking enough, blood volume decreases. This results in lower blood pressure, which can prevent vital organs from receiving the oxygen they need. As preventive cardiologist Dr. Luke Laffin puts it, dehydration means “you’re just not filling up the pipes enough for what your vascular system needs.”

In extreme cases, a severe drop in blood pressure can lead to heart or brain damage, and in the worst scenarios, even be fatal.

Symptoms of Low Blood Pressure

Signs that your blood pressure may be too low include:

• Dizziness or lightheadedness
• Fainting
• Nausea or vomiting
• Blurred vision
• Rapid, shallow breathing
• Fatigue or weakness
• Difficulty concentrating

How Dehydration Can Cause High Blood Pressure

Your body has built-in mechanisms to correct low blood pressure, but sometimes they can overcompensate. When dehydration causes sodium levels in the blood to rise, your body releases a hormone called vasopressin, which helps retain water. However, vasopressin also causes blood vessels to constrict, leading to an increase in blood pressure.

For those already dealing with hypertension, this can be particularly concerning, as it may contribute to even higher blood pressure levels.

The Importance of Staying Hydrated

The best way to keep dehydration-related blood pressure issues at bay is to ensure you’re drinking enough fluids each day.

The National Academies of Science, Engineering, and Medicine suggests a daily fluid intake of about 125 ounces (3.7 liters) for men and 91 ounces (2.7 liters) for women. However, factors such as climate, activity level, and medication use may increase your hydration needs.

“Keeping your body hydrated helps maintain balance in many ways, including regulating blood pressure,” says Dr. Laffin. “Being mindful of your fluid intake can go a long way in preventing potential health risks.”