During periods of extreme heat, we are often told: “Drink water”. But it is also possible to drink too much, to the point of endangering your health. This risk is called hyponatremia.
What is hyponatremia?
Hyponatremia is an abnormal drop in blood sodium (< 135 mmol/L). It occurs when we bring too much water in relation to the salt available, or when we lose too much salt (sweating, certain medications) without compensating.
The blood then becomes “diluted”, the water enters the cells which swelling (including in the brain), which can cause serious complications.
Symptoms to watch for
- Nausea, vomiting
- Headache
- Confusion, disorientation, unusual fatigue
- Oedema, muscle cramps
- Emergency (severe forms): convulsions, coma
Who is most at risk?
- Elderly people : reduced sweating, less water elimination effective.
- Chronic illnesses : kidney or heart failure, diabetes, cancer.
- Medications : diuretics, psychotropic drugs (e.g.: antidepressants).
- Athletes / workers in heat : heavy sweating not compensated by salt.
Why does heatwave increase the risk?
Sweating removes a lot of water (≈99%) and also minerals (including sodium). Drinking only water (tap or bottle) is not always enough to restore balance: you also need a sodium intake via diet or appropriate drinks.
How much to drink safely?
- General population : avoid exceeding 3 to 4 L of liquids/day.
- People at risk : approximately 1.5 L/day (excluding water from food), according to medical advice.
Avoid “chug » : ingesting very large quantities of water in a very short time can be dangerous.
How to hydrate properly during the heatwave?
- Drink regularly in small sips, without forcing yourself to excess.
- Alternate pure water and mineral intake : broths, more sodium mineral waters, salty foods (tomato, olives, cheese in reasonable quantities).
- For exercise and work in heat: consider oral rehydration drinks or mineral water richer in sodium.
- Do not drink several liters at once: divide your intake.
- If you are fragile (age, illness, medications): seek medical advice to adjust your intake.
What to do in the event of symptoms?
- Mild forms : temporarily reduce water intake and consult if there are signs persist.
- Severe signs (confusion, convulsions): call for help immediately.
Key message : during the heatwave, hydrate yourself regularly, but keep the balance: water and minerals.
