Drinking water can help normalize your blood pressure but doesn't necessarily lower your blood pressure unless you are dehydrated. Because your blood is made up of 90% water, the overall volume will decrease when you are dehydrated. When this happens, the body will respond by narrowing blood vessels, causing blood pressure to rise.
If you have chronic (persistent) dehydration, it can make your hypertension (high blood pressure) worse. In some cases, dehydration can also lower your blood pressure.
While drinking water is not a "treatment" for high blood pressure, remaining well hydrated—by drinking six to eight 8-ounce glasses of water per day—may help keep your blood pressure under control along with other health measures.
This article explains how dehydration contributes to hypertension and how drinking water can help maintain or even lower your blood pressure. It also describes the other lifestyle measures that should also be part of your treatment plan if you have high blood pressure.
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How Dehydration and High Blood Pressure Are Linked
Dehydration occurs when the body loses too much water that it needs to function normally. One of the main reasons for this is not drinking enough water or not replenishing water lost to sweat, excessive urination, vomiting, or diarrhea.
According to the Centers for Disease Control and Prevention (CDC), the average adult in the United States consumes 41 ounces of water per day (or roughly 5 cups). People over 60, who are at greater risk of hypertension, drink only 36 ounces (or 4 1/2 cups). That is anywhere from one-half to one-fifth of the recommended daily intake, depending on your age and sex.
This is not to suggest that dehydration "causes" hypertension, but it certainly has the potential to contribute to a disease that affects one in three people in the United States.
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How Dehydration Affects Blood Pressure
Sodium is an essential mineral you get from salt that serves two important roles in your blood pressure. It helps maintain the proper balance of water so that the body's systems are in a constant state of equilibrium (homeostasis). It also helps contract and relax muscles throughout the body, including those in blood vessels.
When sodium levels are abnormally high (hypernatremia) or abnormally low (hyponatremia), these functions can be severely impaired. Even when sodium levels are modestly affected, there can be significant consequences.
When you are dehydrated, the volume of water in your blood goes down, concentrating sodium levels. The increase in sodium, in turn, causes your body to secrete a hormone called vasopressin that prevents the kidneys from releasing water in urine, thereby preventing water loss.
At the same time, vasopressin causes the constriction (narrowing) of blood vessels, thereby increasing blood pressure, sometimes precipitously.
Though studies are lacking as to how much dehydration impacts hypertension, animal studies conducted by Monash University reported that chronic dehydration not only worsens high blood pressure in mice but also increases the risk of severe kidney damage.
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How Much Water Should I Drink?
Drinking the recommended amount of water each day has numerous health benefits, which includes:
- Helping normalize blood pressure
- Maintaining the balance of electrolytes in the body, including sodium
- Improving the transport of oxygen and nutrients to cells
- Regulating body temperature
- Aiding digestion
- Preventing constipation
- Flushing bacteria and toxins from the kidneys and bladder
- Cushioning joints
Most health providers recommend drinking six to eight 8-ounce glasses of water per day to supplement the water you get from the foods.
But this may fall short of your individual needs based on your age, sex, diet, general health, level of physical activity, and even certain medications you take (such as diuretics).
As a general guideline, the National Institute of Sciences recommends the following adequate levels for total water intake for adults in the United States:
- For adult females: 11 cups (2.7 liters or about 91 ounces) daily from all foods and liquids
- For adult males: 15.5 cups (3.7 liters or about 125 ounces) daily from all foods and liquids
In the end, there is no one-size-fits-all solution for everyone. To estimate your individual needs, speak with your healthcare provider—particularly if you have or are at risk of hypertension.
A Word From Verywell
Drinking enough water on a daily basis and staying hydrated is an important way to manage your health and blood pressure.
— CHRISTOPHER LEE, MD, MEDICAL EXPERT BOARD
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Drinks to Limit or Avoid
If you have high blood pressure, it is best to avoid or limit sugary drinks and those that are high in caffeine, including:
- Sports drinks: These drinks are high in sugar and can promote weight gain which contributes to hypertension. These are only recommended to replace electrolytes lost through sweating or severe vomiting or diarrhea.
- Coffee drinks: Flavored coffee drinks are typically high in sugar and can promote weight gain and high blood pressure. Caffeine is also a stimulant that can independently increase your heart rate and blood pressure.
- Energy drinks: Energy drinks are different from sports drinks in that they don't replace electrolytes. These drinks are high in caffeine.
- Alcohol: Having more than three drinks in one sitting can temporarily increase your blood pressure. Repeated binge drinking can lead to long-term hypertension, likely by decreasing the production of nitrous oxide that the body uses to dilate (widen) blood vessels.
Other Lifestyle Choices That Can Help
Keeping well hydrated can help normalize your blood pressure if you've been diagnosed with hypertension or are prehypertensive. But it is not the only lifestyle change you should consider.
The Centers for Disease Control and Prevention (CDC) advises the following measures that can not only help people with hypertension but can also prevent the disease in those with normal blood pressure:
- Eat a heart-healthy diet: This involves eating a variety of foods rich in potassium, fiber, and protein while reducing your intake of salt and saturated fat.
- Achieve and maintain your ideal weight: Your healthcare provider can help you calculate your ideal weight based on your body mass index (BMI).
- Be physically active: Adults should get a minimum of 2 hours and 30 minutes of moderate-intensity exercise every week (or roughly 30 minutes a day, five days a week). This may include brisk walking, swimming, or cycling.
- Get enough sleep: Not getting enough sleep throws off your sleep cycle and causes an imbalance of hormones, including those that regulate blood pressure. Most adults are advised to get seven solid hours of sleep per night. Improving your sleep hygiene can help,
- Reduce your alcohol intake: Alcohol can significantly raise blood pressure. Males should drink no more than two drinks per day, while females should limit their intake to no more than one drink per day. If you cannot stop, speak with your healthcare provider about alcohol treatment.
- Stop smoking: Cigarette smoke causes the constriction of blood vessels which contributes to both high blood pressure and heart disease. No matter how many years you've smoked, stopping at any age can help reverse many of the harms.
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Can Other Drinks Lower Blood Pressure?
There is some evidence that certain drinks other than water may be beneficial to people with high blood pressure. This is not to suggest that they "treat" hypertension, but they are considered "safe" and can help you maintain ample hydration in addition to the water you drink each day.
These include:
- Beet juice: A 2016 study involving 240 participants with hypertension found that a 250-milliliter (8-ounce) serving of red beet juice daily modestly decreasesystolic and diastolic blood pressure after two weeks.
- Tomato juice: A 2019 study involving 481 participants with hypertension or prehypertension concluded that drinking 200 milliliters (6.5 ounces) of unsalted tomato juice daily significantly reduced systolic and diastolic blood pressure after one year.
- Pomegranate juice: A 2017 analysis of eight randomized controlled studies suggested that a 240-milliliter serving of unsweetened pomegranate juice could reduce systolic and diastolic blood pressure in hypertensive people after 12 weeks.
- Cranberry juice: A 2021 study involving 40 adults with hypertension found that two 240-milliliter servings of unsweetened cranberry juice reduced systolic and diastolic blood pressure after eight weeks. Even so, the effect short-lasting with high blood pressure returning once treatment was stopped.
- Low-fat milk: A 2018 study involving 2,649 participants reported that drinking milk lowers blood pressure but that the greatest gains were seen in people who drank low-fat milk. The only group who had no response to milk were those with indications of diabetes or prediabetes.
- Tea: A 2020 review of five studies involving 408 participants concluded that regularly drinking both black and green tea was associated with sustained decreases in systolic and diastolic blood pressure. Green tea appeared to have a more potent effect than black tea.
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Summary
Drinking water can help normalize blood pressure. If you are dehydrated, it can also help lower blood pressure. Drinking water is not a treatment for high blood pressure but it can help you sustain healthier blood pressure, whether you have hypertension or not.
Speak with your healthcare provider to determine how much water you need based on your age, general health, fitness level, and other factors.
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