A glass of water before bed is often recommended as a simple way to stay hydrated overnight. But can that bedtime habit actually protect your heart or reduce the risk of a stroke?

The question was recently posted on the online forum Quora: Is it true that a glass of water before bed reduces the risk of a heart attack or stroke?

We dug deeper and reached out to Dr Swarup Swaraj Pal, Sr. Consultant, Cardiovascular and Thoracic Surgeon, Gleneagles Hospitals, Parel, for answers.

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The answer, as it turns out, isn’t quite as simple as “drink a glass of water before bed and protect your heart.”

“There is no strong evidence that drinking a glass of water immediately before bedtime directly prevents a heart attack or stroke. Cardiovascular health depends more on maintaining adequate hydration throughout the day, controlling blood pressure, managing cholesterol and diabetes, staying active, and following a heart-healthy lifestyle.”

Why does hydration matter, then?

Severe dehydration, can reduce blood volume and make the blood more concentrated, increase clotting risk (Envanto Image)

If a bedtime glass of water doesn’t specifically prevent a cardiovascular event, it is worth understanding why hydration gets linked to heart health in the first place.

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Water helps maintain normal blood volume and circulation. But that doesn’t mean drinking more water at a particular time offers extra protection.

“Drinking water helps maintain normal blood volume and circulation, but there is no evidence that a glass of water before bed significantly ‘thins’ the blood or provides a special protective effect against heart attack or stroke. Adequate hydration is more important than drinking at one specific time.”

What happens during the night?

We naturally go several hours without drinking water while asleep. For most healthy people, this mild overnight dehydration is unlikely to independently trigger a heart attack or stroke.

“Severe dehydration, however, can reduce blood volume and make the blood more concentrated, which may affect circulation and potentially increase clotting risk, particularly in vulnerable individuals.”

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So the concern isn’t that everyone needs a glass of water before sleeping to prevent their blood from becoming dangerously concentrated overnight. It’s about avoiding inadequate hydration in the first place.

Should you drink extra water before bed?

Screenshot of the query posted on Quora

For most people, deliberately drinking a large amount of water just before sleeping isn’t necessary. Maintaining adequate hydration throughout the day matters much more.

“Regular fluid intake based on thirst, weather, activity, and individual needs is generally a better approach than consuming a large amount at bedtime.”

There is also a practical reason not to overdo it: too much water at night can mean repeated trips to the bathroom and disturbed sleep, which “itself can affect cardiovascular health.”

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For some people, drinking extra fluids without medical advice can be particularly inappropriate.

“People with heart failure or kidney disease may have specific fluid restrictions and should follow their doctor’s advice rather than deliberately increasing their water intake.”

So, if you’re thirsty before bed, there is nothing wrong with having some water. But there is no evidence that making it a bedtime ritual specifically protects against heart attack or stroke. For cardiovascular health, staying adequately hydrated throughout the day and managing established risk factors matter far more than when you drink your last glass of water.