The human body needs a lot of water to function properly, and a person may only survive a few days without water. Many other factors, such as a person’s activity level and their environment, also play a vital role, so there is no reliable way to tell how quickly a person can die from dehydration.

Dehydration occurs quickly, causing extreme thirst, fatigue, and ultimately organ failure. A person can go from feeling thirsty and slightly lethargic on the first day without water to organ failure on the third day. Dehydration does not affect everyone in the same way. Each person has a different level of tolerance to dehydration and may be able to survive without water for longer or shorter periods of time than others.

How long can an average person live without water?

A person’s general health can determine how much water they should drink. The body needs plenty of water to perform many essential functions, such as balancing internal temperature and keeping cells alive. Typically, a person can survive without water for about 3 days. However, certain factors, such as how much water an organism needs and how it uses it, can influence this duration.

Factors that can change the amount of water a person needs include:

activity level
general health
bodily factors, such as height and weight

What a person eats can also affect how much water they need to drink. For example, a person who eats foods rich in water, such as fruits, juices or vegetables, does not need to drink as much water as a person who has eaten cereals, breads and other dry foods. The environmental conditions a person finds themselves in also affect how much water their body uses. A person living in a very hot climate will sweat, causing them to lose more water. A person living in an air-conditioned environment will not sweat and therefore will not use as much water.

If a person with diarrhea or vomiting does not have access to water, they will lose water much faster than someone without these problems.

Effects of lack of water

Human beings can only survive for a short time without water, because the body needs it for almost all processes, including:

regulation of body temperature through perspiration and respiration
help digestion by forming saliva and breaking down food
moisten the mucous membranes
help balance the body’s pH
lubrication of joints and spinal cord
help the brain make and use certain hormones
help transport toxins out of cells
eliminate waste through urine and breath
supply oxygen to the whole body.

Without water, the body is unable to function properly and begins to shut down.

The effects of dehydration come on quickly, especially when it’s extremely hot and the person is sweating. The body uses water to produce sweat, which evaporates and lowers body temperature. Without water, the body cannot produce sweat. This can lead to a dangerous increase in body temperature and put pressure on body fluids, including blood. If this leads to a drop in blood volume, less blood circulates through the body, causing a significant drop in blood pressure. This can itself lead to loss of consciousness or worse. At the same time, the mouth becomes dry, and the digestive system slows down.

Water helps the body flush toxins from cells and excrete them through urine and breath. Without water, the body cannot do this effectively, resulting in a buildup of toxins. A buildup of toxins harms the kidneys, which process the elimination of toxins from the body. If the kidneys fail, toxins build up even more, leading to generalized organ failure and death.

Role of diet in dehydration

Although pure water is the main way to absorb liquids, other liquids, such as herbal teas, fruit juices and broths, also contribute to hydration. Also, many foods contain water which replenishes body fluids. Examples are fruits, berries and green vegetables. However, not all foods contribute to the hydration of the body. Very dry and salty foods, such as breaded products, salty crisps, or other dry, packaged snacks, can make dehydration worse. Beverages containing alcohol or caffeine can dehydrate the body more quickly because they cause excessive urination.

Risks associated with dehydration

Dehydration can cause headaches and confusion. Symptoms of dehydration can appear quickly. If the body begins to lose water, it can send signals to the brain to trigger a reaction that the person will notice. Most people are familiar with the minor symptoms of dehydration, such as a very dry mouth or feeling very thirsty.

A study published in the journal Nutrients notes that thirst is the first sign that a person does not have enough water in their body. For most people, drinking when thirsty will provide them with more than enough water to function and thrive. It is crucial to listen to these signals and bring water to the body. As a study in BMC Public Health points out, water makes up 60% of a person’s body weight, and losing just 3% of that weight through water loss can lead to dehydration. If a person ignores these signs or cannot get water, his body will react. The brain will send signals to the body to conserve water and urinate less. It will also slow down the functioning of the kidneys.

Dehydration can cause other noticeable changes in the body, such as:

lethargy or lack of energy
dizziness and confusion
heatstroke and heat cramps
stiff joints that can end up sticking and not working properly
high or unregulated body temperature
brain swelling
sudden changes in blood pressure
epileptic seizures
The person may also be in a state of shock and become unresponsive.

Drinking water regularly helps keep cells healthy, but when a person’s body loses water rapidly, the cells in the body begin to shrink as the water leaves them.


Hydration is essential for human life. While some people are able to survive for weeks without food, they can only survive a few days at most without water. Drinking water and eating foods that contain a lot of water can help prevent dehydration. Without water, dehydration can affect the body quickly. Depending on the environment and the person’s level of exertion, they may notice changes in their body after just a few hours. If a person has diarrhea or vomiting, their body may lose water more quickly.
In general, a person who drinks when thirsty should not be at risk of dehydration.

* criptom strives to transmit health knowledge in a language accessible to all. In NO CASE, the information given can not replace the opinion of a health professional.