Drinking habits

Can you drink too much water?

Can you drink too much water? Yes, although it is rare in everyday life: the salt balance only tips when someone drinks very large amounts in a short time. Specialists speak of dilutional hyponatraemia. Understanding the mechanism is worthwhile, because it also shows why normal drinking habits stay far away from the critical range.

Updated August 2026 · 6 min read

Why can drinking too much water become a problem?

Water is not a hazardous substance, and the body regulates its fluid balance extremely reliably. Things only become critical when intake clearly exceeds excretion. The background: the body keeps the concentration of sodium in the blood within narrow limits. Sodium is involved in transmitting nerve signals, in muscle function and in distributing fluid between the cells and the bloodstream. If someone drinks considerably more in a short time than the kidneys can process, the blood becomes diluted and the sodium level falls.

This so-called dilutional hyponatraemia is the mechanism behind what is colloquially known as “water intoxication”. If the sodium level falls markedly, water shifts into the body's cells, including those of the brain, which can swell as a result. To keep the scale in view: such an imbalance does not arise from one glass too many, but from very large amounts in a very short time or from particular circumstances, which we cover further below.

How much water is too much?

There is no upper limit that applies to everyone; it depends on body weight, kidney function, sweat loss and salt intake. As a rough physiological guide: healthy kidneys can excrete around one litre of fluid per hour. Anyone who drinks considerably more than that over several hours, without losing a corresponding amount of fluid and salts, will at some point overwhelm this system. Documented incidents accordingly involve almost exclusively situations in which several litres were drunk within a few hours – at drinking contests, for instance, or out of misplaced caution at endurance events.

To put normal quantities into perspective: the European Food Safety Authority (EFSA) gives a reference value for total water intake of around 2.0 litres per day for women and 2.5 litres for men, including the water from solid food, which typically accounts for around a fifth to a quarter. That leaves roughly 1.5 to 2 litres as drinks in everyday life. In hot weather, during physical work or sport, it may and should be more; spread across the day, that too is unproblematic.

Who should take particular care?

The risk is best documented in endurance sport. In marathons, long-distance triathlons or long mountain tours, several factors come together: sweat carries away not only water but also salt, people drink “as a precaution” at every aid station, and the exertion itself can curb water excretion via hormonal mechanisms. During long exertion it is therefore safer to drink to thirst than to follow a rigid schedule. For a sense of how much is reasonable on long training days, see the water intake calculator for long sessions. Increased attention is also warranted with:

• diseases of the kidneys, heart or liver, in which the body excretes or distributes fluid less effectively
• medicines that affect the water or salt balance, such as certain diuretics or psychotropic drugs
• mental illnesses involving pathologically increased drinking (polydipsia)
• endurance events lasting several hours, especially with a long time out on the course

If you have a chronic condition or take medication regularly, discuss the drinking quantity that is right for you with your doctor. This article provides general information and is no substitute for medical advice.

What are the warning signs?

Mild hyponatraemia often causes no symptoms, or only non-specific ones. With significant overhydration, the following may occur:

• headaches, light-headedness or unusual tiredness
• nausea and vomiting
• confusion or a striking change in behaviour
• muscle weakness or cramps
• weight gain during a long bout of exercise, an indication that more has been drunk than excreted

If such symptoms occur after very large amounts have been drunk, particularly during or after intense endurance sport, seek medical help immediately. Do not continue drinking in this situation: additional water makes the problem worse.

Why is thirst a reliable signal?

In healthy adults, the sensation of thirst is part of a finely tuned regulatory loop: if the salt concentration in the blood rises even slightly, thirst makes itself felt – long before any meaningful fluid deficit develops. The widespread idea that one must always “pre-empt” thirst is therefore unfounded for healthy people in everyday life. Conversely, constantly drinking without thirst brings no proven additional benefit; what matters is the balance across the day.

Weight, activity and climate all play into how much makes sense for you personally; our hydration calculator provides an individual reference point. And because the opposite is far more common in everyday life: what happens when you drink too little water is covered in a separate article.

A rule of thumb for everyday life

For healthy people, a simple rule of thumb is enough in everyday life: drink to thirst, plan a glass with meals, allow moderately more in hot weather and during exercise, and avoid extreme amounts in one go. Anyone who keeps to this stays far away from any critical threshold.

What you use to cover your daily needs is ultimately a matter of taste. Piz Sardona, a naturally alkaline mineral water with a pH of 8.0, comes from the Castels spring in Mels; the water behind it seeps away at over 2,000 m above sea level in the Sardona Alps by the UNESCO World Heritage Tectonic Arena Sardona and spends around 12 years filtering through layers of rock. More about its origin and mineral values under our water.

Frequently asked questions