The Critical Role of Water in Survival—How Long Can You Go Without It?

Staying hydrated and drinking plenty of water is essential for health and well-being, as the human body is 50-60% water. Without enough water intake, you can experience dehydration, which may cause lightheadedness, fatigue, low blood pressure, heart palpitations, and more.

There are no universal recommendations on how much water to drink each day. Each person's hydration needs vary depending on various factors. Some health experts recommend 11.5 cups of fluid daily for women and 15.5 cups for men as a general guideline.

Not getting enough water for an extended period can have serious consequences. Experts estimate most people can only survive about three days without water (from fluids and food).

What Does Water Do for the Body?

Your body needs water to function properly. Drinking an adequate amount of water can help regulate your body temperature, cushion and lubricate your joints, protect your body's organs and tissues, improve circulation, and support waste elimination like urination and bowel movements.

Drinking water every day offers many health benefits, such as:

• Supports heart health: Research has found that staying well-hydrated may improve heart function and reduce the risk of heart failure.
• Prevents constipation: Dehydration is one of the primary causes of constipation. Drinking plenty of water helps move food and stool through your system and can help promote regular bowel movements.
• Hydrates the skin: Dry skin is often a sign of dehydration, so drinking enough water can benefit your skin health. Some evidence suggests that staying hydrated reduces dryness and prevents premature aging.
• Aids weight management: Water is a zero-calorie beverage. Studies have found that drinking water supports fat loss through increased fat burning. Conversely, not drinking enough water has been linked to increased body weight.
• Supports memory and cognition: Your brain mass is 75% water, so it's important to drink water to maintain this balance. Consistent low water intake can lead to short-term memory loss and disrupt cognitive performance.
• Improves athletic performance: Drinking plenty of water before and after exercise helps your body perform at its peak capacity, while not drinking enough can negatively affect your performance. Research has also found that drinking enough water can help you work out longer and at a higher intensity.
• May promote healthy aging: One study found that people who were well-hydrated appeared to have better health outcomes than people who were under-hydrated. Participants in the study who did not drink much water or other fluids had advanced biological aging, more chronic conditions like heart and lung disease, and died younger.

How Long Can You Go Without Water?

Scientists do not have an exact number for how long a person can survive without water, as this type of study would be unethical. Most experts estimate that the typical person can last about three days with no water before severe dehydration takes its toll and severely disrupts bodily functions.

Older studies have found that depending on a person's age and health status, they may survive 8-21 days.

Factors Affecting Water Needs

Here are some of the factors that can influence your water needs:

• Age
• Activity levels
• Overall health
• Height and weight
• Assigned sex

Health Effects of a Lack of Water

When you do not drink enough water, you risk becoming dehydrated. Signs of dehydration include having a dry mouth, urinating and sweating less than usual, having dark-colored urine, and feeling dizzy.

In severe cases, dehydration can cause life-threatening complications like a drop in blood pressure, a fast heart rate (tachycardia), and possibly death. See a healthcare provider right away if you experience these symptoms or any of the following:

• Lack of urination
• Rapid breathing
• Fainting
• Heart palpitations 
• Confusion
• Lethargy
• Reduced alertness

How Much Water Do You Need a Day?

There is no universal recommendation for how much water you need each day. Your daily fluid intake includes water and fluids from food and other beverages.

The amount of fluids you need each day will vary depending on how you feel, what you are doing, and what the weather is like. Body processes like sweat, urination, bowel movements, and respiration changes can also contribute to your daily water loss, influencing your fluid needs. 

Some health experts suggest a general guideline of 11.5 cups of water per day for women and 15.5 cups per day for men. Food typically provides about 20% of your daily water needs. The remaining 80% should come from plain water and other beverages. This means that, on average, women need to drink about nine cups of water and other beverages, and men should drink about 13 cups.

These guidelines will vary if you are pregnant, breastfeeding, or have a health condition that requires more hydration than the typical adult. People who are breastfeeding may need 16 cups of water a day, while people who are pregnant may need up to 12 cups of water a day.

How To Stay Hydrated

The best way to stay hydrated is to drink plenty of water—or other beverages—each day. Your exact hydration needs will vary based on your age, medical conditions, and activity level. For instance, if you regularly work in high heat, you should drink 8 ounces of water every 15-20 minutes.

Drink fluids in short bursts rather than in large amounts less frequently. Drinking more than 48 ounces of water in one hour could lead to water toxicity, which can cause side effects like fatigue, nausea, vomiting, headaches, blurred vision, confusion, restlessness, irritability, and lethargy.

Make sure to drink extra fluids when you are sick. Don't wait until you are dehydrated to drink fluids. You will need extra water if you have a fever, vomiting, or diarrhea.

In Case of Emergency

If you are in a natural disaster area and the water has been contaminated, there are a few ways you can stay hydrated. Eat fruits and vegetables with high water content, such as cucumbers and watermelon. You can also drink the water in canned fruits and vegetables. If you have ice cubes that were frozen before the water became contaminated, melt them and drink the water.

The Federal Emergency Management Association (FEMA) suggests boiling contaminated water and then skimming the clean water above the sediment. You can also filter the water through a clean cloth, paper towel, or coffee filter before boiling.

In an emergency, you can use water from your home's water heater tank (the drinking water system, not the heating system). Boil the water before drinking.

A Quick Review

Drinking water daily is essential for maintaining bodily functions and supporting overall health. Not getting enough water can lead to dehydration, which can cause fatigue, heart palpitations, low blood pressure, and, in severe cases, death.

Most experts suggest the average person can survive without water for three days.

While there is no standard recommendation for daily water intake, most experts suggest drinking 9-11 cups of water a day to stay optimally hydrated. Individual water needs may depend on age, sex, activity level, health status, medications, and climate.