What Happens When You Drink Too Much Water?

It's no secret that staying hydrated is important, but can you overdo it? For people with healthy kidneys, drinking plenty of water is typically safe. In some rare cases, drinking too much water can result in water toxicity.

Though it's uncommon, it's important to understand what can happen if you drink too much water so you can avoid it.

Understanding Water Toxicity

The body relies on both water and electrolytes, such as sodium and potassium, to maintain a healthy level of hydration. Electrolytes play an important role in supporting heart, brain and muscle function, and the balance between electrolyte and water levels in the body is key. It is possible to drink more water than your body can handle at one time, and drinking too much water can lead to water toxicity. When this happens, the extra water is absorbed into cells in the body, causing them to swell. Swelling of brain cells can lead to excess pressure inside your head, which can cause confusion, headache and drowsiness. Nausea and vomiting or muscle cramping may also occur.

Some causes of water toxicity include:

• Rehydrating with water too fast after very long workouts without replenishing lost electrolytes.
• Craving water excessively, a condition called psychogenic polydipsia.
• Taking certain medications.
• Having kidney disease or failure.
• Replenishing water in conditions when the antidiuretic hormone (ADH) levels are high. ADH helps the body decide how much water to keep or let go. Too much ADH means the body holds onto more water.
• Participating in water drinking contests.

How Much Water Is Too Much Water?

Your recommended daily fluid intake depends on factors such as age, gender, physical activity and overall health. The daily recommendations are about 11.5 cups for women and 15.5 cups for men.

While there isn't a specific limit on how much water is “too much,” drinking small amounts more frequently is generally considered a better practice for hydration than large quantities all at once. As a safety guideline to avoid water toxicity, Centers for Disease Control and Prevention (CDC) recommends not drinking more than 48 ounces (or 6 cups) of fluids per hour.

“As a general rule, the body thrives on balance — and water intake is no exception,” said Jennifer Williams, MPH, a nutrition scientist at Abbott specializing in hydration. “To avoid water toxicity, it's important to drink when you're thirsty and listen to your body's cues to ensure hydration without overconsumption.”

Health Effects of Water Toxicity

What happens when you drink too much water? On a cellular level, drinking too much water can cause low sodium in the blood — a condition called hyponatremia — which can cause serious complications in your body, especially if it happens suddenly. Many other factors can contribute to low sodium levels and the condition should always be taken seriously.

Catching it early is key to avoiding more serious issues like seizures, coma or even death. Be aware of the symptoms and seek medical help right away if you experience any of the following:

• Headache
• Nausea
• Vomiting
• Confusion
• Drowsiness or fatigue
• Weak or spasming muscles

How to Avoid Water Toxicity

An easy way to check your hydration level is to look at your urine color. A pale yellow color means you're likely on track with good hydration. The darker the color, the less hydrated you are. If you're feeling thirsty, drink some water. If you're always thirsty or feeling the urge to drink more than usual, chat with a healthcare provider. And remember, the body prefers a balance of fluid and electrolytes, so athletes and those participating in strenuous exercise should take care to replenish electrolytes lost through sweat by considering an electrolyte drink before and after exertion.

The bottom line: Water toxicity is not typically something the average person needs to worry about, and it should not deter you from hydrating properly. Aim for healthy hydration every day and talk to your doctor if you have concerns.