Drinking water is often seen as a simple habit to protect cardiovascular health. However, according to experts, water only supports blood pressure control in certain cases, not the dose of medicine that directly reduces blood pressure.
According to Dr. Anisha Shah, a member of Verywell Health Medical Experts Council, dehydration is an easily overlooked factor but can increase blood pressure. “Blood contains about 90% water. When the body is dehydrated, blood volume decreases, blood vessels contract and blood pressure tends to increase,” she analyzed.
Why can dehydration increase blood pressure?
Dehydration occurs when the amount of water excreted exceeds the amount ingested, often due to insufficient drinking, heavy sweating, vomiting or prolonged diarrhea. At that time, sodium levels in the blood increase, stimulating the body to secrete the hormone vasopressin to retain water. As a result, blood vessels contract, causing blood pressure to increase, sometimes increasing quite suddenly.
Some symptoms suggesting dehydration with high blood pressure include dizziness, fatigue, severe thirst, dry mouth, dark urine, and rapid heartbeat. In these cases, drinking enough water can help bring blood pressure back to a more stable level.
Dehydration also causes low blood pressure
In the opposite direction, if the body loses too much fluid, especially over 15% of the total volume of fluid, blood pressure can drop sharply due to reduced blood volume. This condition causes organs not to be supplied with enough oxygen and risks leading to shock, multiple organ failure if not replenished with fluid in time.
Warning signs include cold, pale skin, fatigue, confusion, rapid and shallow breathing, and even fainting. This is an emergency situation requiring immediate medical intervention.
Does drinking plenty of water help lower blood pressure?
The answer is not necessarily. Drinking enough water helps prevent blood pressure from increasing due to dehydration, but it is not a treatment for chronic hypertension. On the contrary, drinking too much water can also cause fluid overload, increasing blood volume and pushing blood pressure higher, especially in people with heart failure, cirrhosis or eating salty food.
Research in Sweden shows that adding about 2 liters of water per day can slightly increase blood pressure during the day. For healthy people, this effect is usually transient, but for people with underlying cardiovascular disease, this is a matter of caution.
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