How Much Water Should You Drink a Day?

The idea that you must drink eight glasses a day to stay hydrated is a myth. So, how much water should you drink in a day?

The amount of water you really need depends on your overall fluid loss and the number of water-rich foods you consume, as well as your electrolyte status, activity levels, and body temperature. 

Let’s take a look at how to maintain optimal hydration and learn why drinking excessive amounts of plain water without electrolytes can actually worsen dehydration. 

The 8 glasses of water per day myth

You probably have heard the recommendations to drink at least eight glasses of water or half of your body weight in fluid ounces daily to maintain water balance and stay hydrated. 

However, neither approach is accurate as your body’s fluid needs depend on many factors, including body composition, activity levels, dietary habits, climate, and overall health. 

People who engage in intense physical activity lose fluids quickly through sweat and, therefore, require a higher water intake than less active individuals.

Hot temperatures also increase water loss, and certain health conditions, such as fever or diarrhea, can significantly elevate fluid requirements. 

Body weight is another factor determining how much water you need to drink. Those with a higher body weight generally require more fluids to maintain proper hydration levels, as their bodies have more tissue to support. 

Additionally, dietary habits are often overlooked when evaluating hydration needs. However, water-rich foods such as vegetables, soups, and stews can significantly contribute to daily fluid requirements. 

Drinking caffeinated beverages as well as sweet drinks can also increase water loss as both caffeine and sugar have diuretic properties that increase urine production. 

This explains why sports drinks cause dehydration and weight gain. These beverages are typically packed with caffeine and sugars, making them less than ideal options to promote proper hydration. 

Watch the video below to learn more about why drinking eight glasses of water daily is a myth. 

How much water should you drink a day? 

Another widespread misconception about hydration is the belief that waiting until you're thirsty means you're already dehydrated.

However, this is incorrect. Feeling thirsty is actually your body's natural and effective signal that it needs more water, not a sign that you're already dangerously dehydrated. Thirst is an early indicator that prompts you to drink fluids before dehydration becomes significant. 

While it's important to stay mindful of your fluid intake, especially during intense activity or hot weather, being guided by thirst cues is generally a reliable way to maintain adequate hydration for most people.

A study published in Sports Medicine confirms the effectiveness of drinking water to thirst. The authors summarize, “Given predicted fluid requirements for differing exercise durations, intensities, environments, and body sizes, drink-to-thirst fluid intake will be sufficient to meet needs.”

The study also highlights the potential benefits of a planned hydration strategy for prolonged and intense activity, especially in hot and humid climates, to maintain optimal performance levels while minimizing the risk of dehydration.  

Although drinking when you feel thirsty is an effective strategy, older people are at an increased risk of dehydration due to age-related physiological changes that can affect their ability to recognize thirst. 

Therefore, it’s recommended that older adults use a refillable water bottle and establish a regular drinking schedule to ensure adequate fluid intake throughout the day.

Signs of dehydration

Adequate fluid levels are essential to maintaining crucial physiological functions, and even mild dehydration can impair cognitive performance, reduce physical endurance, and disrupt normal bodily processes.

Here are common symptoms indicative of dehydration:

• Dry mouth

• Decreased need to urinate

• Dark colored urine

• Recurring urinary tract infections

• Constipation

• Irritability

• Poor memory 

• Muscle weakness or cramps

• Dizziness

• Low blood pressure

In addition, since water is essential for nearly all biochemical processes, dehydration can exacerbate various health conditions, including impaired kidney function, kidney stones, diabetes, and cardiovascular disease.

Severe dehydration can be life-threatening and may lead to serious complications such as kidney failure, seizures, heatstroke, and even coma and death. 

Symptoms of severe dehydration, such as extreme thirst, dry mucous membranes, sunken eyes, minimal urinary output, and deliriousness, require immediate medical attention to prevent potentially fatal outcomes.

Danger of drinking too much water

Although daily water intake is essential to maintain the body's fluid balance, drinking too much water can cause hyponatremia, also known as water intoxication.

Excessive fluid intake triggers increased urinary output, which also causes the loss of essential electrolytes and dilutes the concentrations of sodium in the bloodstream.

Sodium plays a crucial role in maintaining the balance of fluids inside and outside of cells. When sodium concentrations drop significantly, fluids shift into cells, which results in the swelling of cells and tissues.

Water-related swelling is particularly dangerous in the brain, as it can lead to increased intracranial pressure. This can cause complications such as severe headaches, confusion, seizures, and, in extreme cases, coma, permanent brain damage, and death.

Research published in BMJ Open found that hyponatremia occurs when oral intake of electrolyte-free fluids exceeds the kidneys' capacity to excrete water. 

The study suggests that water intake of around one liter (34 ounces) per hour, especially when consumed over an extended period, can lead to sodium imbalances and hyponatremia.  

“While hyponatremia is rare, drinking too much plain water can quickly deplete essential electrolytes, including potassium, magnesium, calcium, and chloride,” explains Dr. Berg. “This can lead to muscle cramps, headaches, fatigue, and heart problems.”

How to maintain optimal hydration 

Although replacing lost fluids is crucial, drinking plain water isn’t the best way to stay hydrated, as it doesn’t replenish electrolytes lost through sweat, urine, and other bodily functions. 

Electrolytes, especially sodium and potassium, are crucial for maintaining fluid balance and regulating water movement into and out of cells. This explains why electrolyte imbalances can worsen dehydration despite plenty of fluid intake. 

To maintain optimal hydration, it’s vital to ensure adequate water intake and replenish lost electrolytes. 

However, it’s recommended to avoid sports drinks, which often contain sugar and caffeine, both of which have dehydrating effects. Instead, use a sugar-free electrolyte powder that can easily be mixed with water.

Opt for electrolyte powders with at least 1000 milligrams of potassium and no more than 40 milligrams of sodium per serving. This sodium-to-potassium ratio has been linked to optimal fluid balance and cardiovascular health. 

You can also prepare your own electrolyte drink with potassium at home to replenish lost electrolytes and maintain fluid balance. 

In addition, it’s crucial to avoid dehydrating drinks such as alcohol, caffeinated and sugary beverages, sodas, fruit juices, and energy drinks. 

While some recommendations suggest consuming plenty of fresh or cooked fruits to support fluid balance, fruits may not offer adequate concentrations of electrolytes, leaving you at risk of dehydration. 

In addition, fruits such as bananas, grapes, oranges, and nectarines are also typically high in sugar, which has diuretic effects and may exacerbate fluid and electrolyte loss. 

Key takeaways

Daily fluid intake is crucial to staying hydrated, but how much water should you drink a day? 

Fluid needs vary significantly based on age, weight, activity level, climate, and overall health, and the most effective approach is to listen to your body and drink when you’re thirsty.

In addition, plain water isn’t enough to maintain the body’s fluid levels, and it’s crucial to replenish lost electrolytes daily. Incorporating a potassium-rich electrolyte powder is an easy and convenient option to support optimal hydration and maintain vital bodily functions.

FAQ

1. How much water should you drink every day?

The amount of water you should drink daily depends on your activity levels, the climate you are exposed to, your health status, and your dietary habits. 

The most effective strategy to promote optimal fluid balance is to drink when thirsty and replenish lost electrolytes with a sugar-free electrolyte powder containing around 1000 milligrams of potassium per serving. 

2. Is 64 ounces of water a day enough?

Whether 64 ounces of water a day is adequate depends on your rate of fluid loss, which is determined by factors such as physical activity, climate, and overall health. 

Increased fluid loss due to physical activity, hot weather, or certain health conditions may require a higher water intake. In contrast, less active individuals in cooler environments might need less than 64 ounces of water daily. 

3. How do I know if I’m dehydrated?

Common symptoms of dehydration include excessive thirst, a dry mouth, dark-colored urine, dizziness, headaches, and fatigue.

Severe dehydration can lead to very dry skin, sunken eyes, rapid heartbeat, and confusion and requires immediate medical attention to prevent potentially severe or even fatal complications. 

4. Can you be dehydrated even if you drink a lot of water?

Yes, drinking only plain water or other beverages without adequate electrolyte concentrations can lead to dehydration. 

Excessive water intake without balancing electrolytes can dilute essential minerals such as potassium, chloride, and sodium, leading to electrolyte imbalances that impair the body's ability to regulate fluid balance and maintain adequate hydration.

5. Is a gallon of water a day too much?

Drinking a gallon of water, especially in a short period of time, can cause hyponatremia, a potentially serious dilution of sodium concentrations in the bloodstream caused by excessive water intake. 

However, those engaging in endurance exercise or working in hot environments may require larger amounts of water and adequate electrolyte replacement strategies to stay hydrated.

6. Can drinking a lot of water help weight loss?

Water intake doesn’t directly help you lose weight or flush fat from the body. However, drinking plenty of water and replacing lost electrolytes can support weight loss by increasing feelings of fullness, which may reduce calorie consumption.

Sources

1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5790864/ 

2. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8663108/