Too Much of a Good Thing? Doctors Also Warn Against Overhydration During Heatwaves
As record temperatures sweep across Europe, public health campaigns continue to urge hydration. But doctors are also warning about a lesser-known risk: drinking too much water, too quickly.
According to Dr. Stephanie Widmer, a medical toxicologist and emergency physician quoted in Fréquence Médicale, overhydration — or water intoxication — can be just as dangerous as dehydration. While rare, it is most likely to occur during extreme heat when people chug large quantities of water in a short period of time.
“The symptoms can be subtle at first — nausea, disorientation, and fatigue,” Dr. Widmer explains. “But in serious cases, overhydration can cause brain swelling, leading to seizures, coma, or even death.”
The danger lies not just in how much water is consumed, but how fast. Drinking more than one liter per hour consistently over several hours can overwhelm the kidneys and disrupt the body’s sodium balance — a condition known as hyponatremia.
To stay safe, experts recommend:
- Drinking slowly and consistently throughout the day.
- Avoiding large amounts of water in short bursts (e.g., three glasses at once after hours without drinking).
- Limiting water intake to no more than one liter per hour.
In times of extreme heat, it’s crucial to find the right balance. “Hydration is vital, but moderation and timing matter just as much as quantity,” Dr. Widmer said.
As climate extremes become more frequent, both under- and over-hydration are emerging as serious public health risks. Montse Aguilar’s case is a tragic reminder that heat-related illness can strike quickly — and that both individuals and institutions must adapt to protect those most exposed.
