Dehydration and Blood Pressure: What’s the Link?

• Evidence suggests a link between hydration status and blood pressure.
• Being dehydrated is associated with an increased risk of high blood pressure.
• Stay hydrated by drinking plenty of water and eating hydrating foods.

Some media outlets have reported that as much as three-quarters of Americans are dehydrated. And though there is no science to support this specific claim, there is evidence that 17% to 28% of older adults are dehydrated. Older adults are also at a higher risk of developing high blood pressure (hypertension), the risk of which increases as we age; and 9 out of 10 Americans will develop high blood pressure during their lifetimes.

So, could there be a link between hydration status and blood pressure? Research suggests yes, and that frequently being dehydrated may increase one’s risk of developing high blood pressure. This could be a problem, considering that the average American adult drinks only around 44 ounces of water daily, which does not meet the daily recommendations.

Let’s take a closer look at this connection and how you can reduce your risk of both dehydration and high blood pressure.

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Dehydration and Blood Pressure

When homeostasis, which is a state of equilibrium, is even slightly disturbed, your amazing body has thousands of backup scenarios to initiate to immediately stabilize the situation and keep things running smoothly. The body’s response to early dehydration is a great example!

In the early stages of dehydration, blood volume (the amount of blood circulating in the body) decreases. This is because water makes up over half of your blood volume. Decreased blood volume also causes an increased concentration of sodium in your blood. For reference, a normal range of blood sodium levels is considered 135 to 145 mEq/L. So, a value at the upper end of this range or above would be considered mild dehydration.

The body does two things when it senses changes in blood volume and sodium levels. The first is to initiate thirst in hopes you’ll be prompted to find some hydration, and the second is to trigger the secretion of anti-diuretic hormone (ADH). The increase in ADH (also known as vasopressin) prompts the kidneys to temporarily retain water to prevent fluid loss (such as from urination) and to keep sodium concentration from increasing further. It also constricts blood vessels, which causes a temporary increase in blood pressure. Since blood volume is low, this increase in pressure is essential to help blood circulate. Once the rehydration process starts, ADH levels slowly decline, and pressure returns to where it was previously.

So now you see how and why blood pressure increases with short-term dehydration, but what if you’re chronically or frequently dehydrated?

One study found that high levels of sodium in the blood due to frequent dehydration may increase the risk of heart failure by 39%. And according to the American Heart Association, high blood pressure is one of the most common causes of heart failure. Another study echoes these findings. This study suggests that people with higher levels of sodium in their blood have a 13% to 29% higher risk of hypertension, with a 20% higher risk of heart failure.

So how do you know if your blood pressure is running high? According to the AHA, there are two stages of hypertension: stages 1 and 2. Stage 1 is when your blood pressure regularly ranges between 130-139/80-89 mm Hg, whereas stage 2 is when your blood pressure is 140/90 mm Hg or higher.

Ways to Stay Hydrated

• Water: Plain water is perhaps the most obvious way to stay hydrated. To get and stay well-hydrated, women should aim for 11.5 cups of water per day, and men, 15.5 cups. Not a fan of plain water? Try infusing flavor into your H2O with citrus fruits, berries or herbs, like mint. Or combine several flavors, like we do in our Lemon, Cucumber & Mint Water.
• Food: If you have a difficult time slugging down enough water each day, you’ll be happy to know that you can eat your fluids, too. Berries, watermelon, oranges, cucumbers, bell peppers and celery are all fluid-filled produce to help you meet your hydration goals.
• Electrolyte Drinks: When you think of electrolyte drinks, you may immediately think of sports drinks in bright colors and fruity flavors. And while those do have their place—like if you’re working in extreme heat and sweating a lot—using them to simply meet your daily hydration needs might not be the best thing, as too many electrolytes can be harmful. With that said, if you want to switch your drinks up, especially if you feel you would benefit from some natural electrolytes, look no further than coconut water, aka nature’s sports drink. Coconut water naturally contains potassium, sodium, magnesium and calcium—all essential minerals and electrolytes.

Our Expert Take

It’s probably wise to consider an ongoing lack of adequate hydration as a risk factor for hypertension. This risk seems to stem from high levels of ADH and subsequent changes to blood pressure and the health of blood vessels that occur over time. While the body’s backup plan when it senses dehydration is lifesaving, the response isn’t intended to have to kick in regularly, so help it out and make staying well-hydrated a daily goal. And remember, just because high blood pressure is common, it doesn’t mean it’s not harmful. Hypertension is a risk factor for heart disease and stroke, so keep tabs on your numbers, stay hydrated and follow medical advice for lowering it if necessary.