Can drinking too much water be dangerous?
Guideline- USA
- NFHS
- NFHS SMAC position statements
- Heat illness
- Hydration
- Youth and high school sports
- Summer sports
- 2025 guidance
- Coaches
- Parents
Yes, though it's rare. NFHS hydration guidance (October 2025) warns about hyponatremia: a potentially deadly condition caused by drinking far more water or other low-sodium fluid (including most sports drinks) than is lost through sweat. Too much water dilutes the sodium in the blood to dangerous levels.
- It's most common in endurance events, such as marathons, when people drink large amounts over several hours.
- Signs: disorientation, altered mental status, headache, lethargy and seizures.
- Suspected hyponatremia is a medical emergency. Call 911. It can only be confirmed with a blood test and is treated in hospital with high-sodium IV fluids.
When rehydrating after exercise, NFHS cautions that drinking an excessive amount in a short time can be dangerous.
Added 21 Oct 2026