More than 60% of the adult human body is made of water. So it makes sense that it’s an important part of our life. We can go over three weeks without food, but not water. So how long can you go without water?

We set out to find the answer.

How long can you live without water?

At age 74, Mahatma Gandhi survived 21 days of complete starvation, only allowing himself infrequent sips of water. 

The adult body is made of more than 60% water. In fact, there isn’t a cell in your body that can live without water. It acts as a lubricant for our joints, regulates our body temperature through sweating and respiration, and helps to flush waste – every living cell in your body needs it to function. 

Unlike food, the maximum time an individual can go without water seems to be a week. But that estimate is even shorter in difficult conditions, like heat. One week is actually longer than the average person would survive. Three to four days would be more typical. 

The 7-day estimate is based on observations of people at the end of their lives, when food and water intake has been stopped, according to Randall K. Packer, a professor of biology at George Washington University.

“You can go 100 hours without drinking at an average temperature outdoors,” says Claude Piantadosi of Duke University. “If it’s cooler, you can go a little longer. If you are exposed to direct sunlight, it’s less.” 

The effects of dehydration

Your body is losing water all day. Nearly every function of our body is using up water. We know our body uses water when we sweat, but it also uses it when you go to the bathroom, and even when we exhale.

“Under extreme conditions an adult can lose 1 to 1.5 liters of sweat per hour,“ Packer wrote in a 2002 article for Scientific American. ”If that lost water is not replaced, the total volume of body fluid can fall quickly and, most dangerously, blood volume may drop.“

One study showed that a water loss of 1.36% from exercise affected mood and concentration and increased the frequency of headaches. Other studies show that mild dehydration (1–3% of body weight) caused by exercise or heat can harm many other aspects of brain function.

Longest someone has survived without water

So what’s the longest someone has gone without water? Although the record isn’t completely clear, the longest reported time someone has gone without water was 18 days. 

Andreas Mihavecz, an 18-year-old Austrian man, was apparently accidentally left in a holding cell for 18 days in 1979. But it’s hard to point to this as a clear record since he allegedly licked condensation off the walls of the prison.

Dehydration can happen faster than you might think

Dehydration can happen sooner than you might expect. Especially during intense workouts or extreme heat. 

The symptoms of dehydration can appear differently depending upon your age. One thing is certain though: your thirst isn't always a reliable early indicator of your body's need for water. Some people, like older adults, don't feel thirsty until they're already dehydrated. 

To be safe, it's important to increase water intake while working out, during hot weather, and when you're ill.

The symptoms of dehydration might look different for you than your child.

Dehydration symptoms for an infant or young child

• Dry mouth and tongue
• No tears when crying
• No wet diapers for three hours
• Sunken eyes, cheeks
• Sunken soft spot on top of the skull
• Listlessness or irritability

Dehydration symptoms for an adult

• Extreme thirst
• Less frequent urination
• Dark-colored urine
• Fatigue
• Dizziness
• Confusion

Hydration sources

It’s true that we get some water from our food, but regularly drinking water throughout your day should be your main source of water intake. During extreme heat or when your body is already dehydrated, be sure to avoid alcohol because it actually causes the body to lose more water than normal through excessive urination. 

The best way to stay hydrated

The best way to stay hydrated is to be sure you are drinking water throughout your day – not only when you’re thirsty or working out. Grab a reusable water bottle today, bring it with you, and never be without water no matter where your day might take you.