If you’ve drunk too much water and feel bloated, nauseous, or headachy, the first thing to do is stop drinking any more fluids. Your kidneys can process roughly 600 to 900 milliliters (about 20 to 30 ounces) of water per hour, so if you’ve exceeded that pace, your body simply needs time to catch up. In most cases, mild overhydration resolves on its own. But in rare, severe cases, drinking far too much water too fast can dangerously dilute the sodium in your blood, a condition called hyponatremia, which requires emergency medical care.
What to Do Right Now
Stop all fluid intake immediately. This is the single most important step. If you’re feeling nauseous, bloated, or have a mild headache, these are early warning signs that you’ve overloaded your system, and continuing to drink will make things worse.
While you wait for your body to process the excess water, eating a salty snack like crackers, pretzels, or salted nuts can help. Sodium is what gets diluted when you drink too much, so a small amount of salt works in your favor. A sports drink with electrolytes can also help restore balance, though you should sip it slowly rather than gulping more liquid into an already full stomach.
Avoid lying flat if you feel very bloated or nauseous. Sitting upright or walking gently can ease discomfort and help your kidneys do their job. You’ll likely need to urinate frequently over the next hour or two as your body clears the excess fluid. That’s a good sign.
Recognizing Mild vs. Dangerous Symptoms
Most people who drink too much water experience mild, temporary discomfort. The early signs include nausea, a bloated stomach, headache, and muscle cramps. These typically resolve within a few hours as your kidneys filter out the extra fluid.
The situation becomes dangerous when excess water dilutes blood sodium below normal levels. At healthy levels, sodium sits between 136 and 145 milliequivalents per liter. Mild hyponatremia (130 to 134) may cause fatigue and slight nausea. Moderate hyponatremia (125 to 129) brings on confusion, drowsiness, and muscle weakness. Severe hyponatremia (below 125) can cause seizures, delirium, coma, and death.
Seek emergency care if you or someone nearby develops confusion, persistent vomiting, seizures, or loses consciousness after drinking large amounts of water. These symptoms mean the brain is swelling from the fluid imbalance, and that requires hospital treatment.
How Water Intoxication Happens
Your kidneys are remarkably efficient. A healthy adult’s kidneys can produce up to 15 to 22 liters of urine in a 24-hour period when working at maximum capacity. But there’s a limit to how fast they can work in any given hour. When you drink water faster than your kidneys can excrete it, the excess water enters your bloodstream and dilutes sodium and other electrolytes.
Sodium plays a critical role in regulating fluid balance between your cells and bloodstream. When sodium levels drop, water flows into cells through osmosis, causing them to swell. Most cells can tolerate some swelling, but brain cells are enclosed by the skull and have no room to expand. That’s why severe hyponatremia primarily shows up as neurological symptoms: confusion, seizures, and in extreme cases, brain herniation.
Who Is Most at Risk
Water intoxication is rare in everyday life, but certain situations raise the risk significantly.
- Endurance athletes are among the most common cases. Marathon runners and ultramarathon participants sometimes drink water aggressively during events without replacing electrolytes, especially when they’re told to “stay hydrated” without specific guidance on how much.
- People on certain medications face a lower threshold for trouble. Thiazide-type blood pressure medications are a well-documented cause of hyponatremia, even at normal water intake. Some antidepressants can also affect how your kidneys handle water by increasing the release of a hormone that tells your body to retain fluid.
- Older adults have reduced kidney function and are more likely to take medications that affect sodium balance.
- People with smaller body size have less blood volume, so the same amount of excess water causes a proportionally larger dilution of sodium.
What Happens at the Hospital
If water intoxication is severe enough to require emergency treatment, doctors focus on carefully raising sodium levels back to a safe range. The key word is “carefully.” Correcting sodium too quickly can cause a separate and serious neurological condition where the protective coating around nerve cells breaks down, potentially leading to lasting brain damage.
The target is to raise blood sodium by about 4 to 6 milliequivalents per liter over the first few hours, which is usually enough to reduce brain swelling and stop symptoms like seizures. Doctors will not try to bring sodium all the way back to normal in one session. The upper limit for correction is typically 8 milliequivalents per liter over a full 24-hour period. Treatment is done in a monitored setting with frequent blood draws to track progress.
How Much Water Is Actually Too Much
There’s no single number that applies to everyone, because body size, activity level, heat exposure, and kidney health all affect how much water you need and how quickly you can process it. As a general baseline, research suggests most healthy adults get enough total fluid from about 11.5 cups (2.7 liters) for women to 15.5 cups (3.7 liters) for men per day, and that includes water from food and other beverages.
The more useful guideline is about pace rather than total volume. Spreading your water intake throughout the day is far safer than drinking large amounts in a short window. If you’re exercising heavily or spending time in heat, replace electrolytes alongside water rather than drinking water alone. Sports drinks, electrolyte tablets, or even lightly salted water can help maintain the balance your body needs.
A practical rule: if your urine is consistently clear and you’re urinating very frequently, you’re likely drinking more than your body needs. Pale yellow urine is a sign of good hydration without overdoing it.