In this Article (Index)
- What is Dehydration?
- What Causes Dehydration?
- Risk Factors
- Signs of Dehydration
- Levels of Dehydration
- How does the body lose water?
- Water loss: Urine
- Water loss: Sweat
- Treating Dehydration
- DIY Oral Rehydration Salts (ORS) Recipe
- Avoid Diuretic drinks
- "Pee" color chart
- Keep Hydrated
- When to see a doctor?
- Complications caused by dehydration
What is Dehydration?
Dehydration happens when your body loses more fluid than it takes in.
This loss of fluids has an impact on body functions and disrupts its metabolic processes.
Levels of Dehydration
A loss of up to 5% of your body fluids is called Mild dehydration. Its symptoms are dry mouth, feeling thirsty and a drop in the frequency of urination. Some people may feel tired and experience cramps.
It is usually tolerated without serious consequences. But it can disrupt mood and impair short-term memory and cognitive performance in children, young and older adults
It is a condition that is solved very easily by drinking water to replenish the body's fluids.
A 5 to 10% dehydration is considered Moderate Dehydration.
Athletes can usually lose between 6 and 10% of body weight during athletic events. Water loss causes a decrease in physical performance starting at 2% dehydration levels.
Moderately dehydrated people may feel fatigued, confused, and dizzy. Athletes will notice a drop in endurance and motivation.
Drinking water or sports drinks usually reverses Moderate dehydration.
Extreme cases of dehydration with a loss of 10 to 15% of body fluids are known as Severe Dehydration.
This causes mental deterioration, severe thirst, increased heartbeat rate, and quickened breathing. This is a life-threatening condition and a person with severe dehydration needs immediate medical treatment.
How does the body lose water?
Water loss takes place almost constantly, and several mechanisms cause it:
Even in cases of severe dehydration, urine production continues. The kidneys produce urine to rid the body of urea which is a toxic nitrogen-containing compound that is formed when amino acids that form proteins are broken down in the liver.
Urine output can drop to one pint (0.5 liters) per day in dehydrated people (normal output is around 3 pints or 1.5 liters).
The color of urine (See the pee color chart below) is a good indicator of dehydration: it can range from dark brown in severe dehydration cases to clear or transparent yellow in normally hydrated people.
Sweat is used by the body to regulate its temperature: as the sweat evaporates from the surface of the skin it draws body heat and produces a cooling effect.
The amount of water lost by sweating can range from a normal value of 1 pint (0.5 liters) to up to half a gallon (2 liters) during hot weather or vigorous exercise or under very dry conditions.
You can see the water lost while you breathe when you exhale during cold weather: the warm water vapor in your breath condenses in contact with the cold air forming a foggy cloud.
You lose water with every breath you take. But the total amount is rather small: roughly two cups of water (0.4 liters) daily.
About one-half cup of water is lost daily through bowel movements (0.1 liter). The large intestine is very efficient at recovering water from stool and recycling it back into the body, but a small quantity remains in the stool.
Watery loose stools can provoke a serious loss of water, a condition known as diarrhea.
If your bowel movements are watery stools three or more times a day, you are suffering from diarrhea. It causes not only the loss of water but also of ions such as sodium and potassium. This can harm your health: Loss of electrolytes can cause twitching, weakness, seizures, and disturbed heartbeat.
Many body functions use electricity, and the electric current is provided by ions, which are charged atoms, also known as "electrolytes".
When minerals dissolve in the body's internal fluids, the molecules that compose them break apart and acquire an electric charge, becoming ions.
Common salt dissociates into sodium and chloride ions. Other examples of ions are calcium, potassium, and bicarbonate.
Our body needs a stable balance of electrolytes to maintain its processes working in healthily.
To maintain an electrolyte balance during cases of dehydration, oral rehydration salts are used. These are either commercially prepared mixtures or "home-made" solutions, see our Homemade Oral Rehydration Salts recipe further down.
Diuretics are substances that increase the output of urine by the body.
Alcohol is a diuretic: for every unit of alcohol that you drink (where one unit is roughly 0.3 oz - 8 g of alcohol), your body will lose 2.7 fl oz (80 ml) of water.
Caffeine is also slightly diuretic (coffee, tea, energy drinks, and cola drinks all contain caffeine), but over 300 mg of caffeine per day is needed to have a diuretic effect.
Yes, they do and they count against your daily water requirement.
The following table shows the average (values can vary quite a bit) caffeine content in one cup or glass of some common beverages:
Caffeine per cup or glass
What Causes Dehydration?
Dehydration often happens for very simple reasons:
- Not drinking enough water because you are too busy.
- Increased water loss due to strenuous exercise or working outdoors in hot or dry weather.
- Lower water intake during hikes or while camping due to lack of access to safe drinking water.
- Not hydrating during flights (you should drink about 8 ounces of water each hour you fly - roughly 1 cup of water per hour).
Medical conditions may also provoke dehydration:
- Diarrhea. As mentioned further up, it can cause a sudden loss of water and electrolytes.
- Vomiting. Also causes a tremendous loss of fluids and electrolytes.
- Fever. Higher body temperature increases the loss of fluids.
- Increased urination. As in the case of diabetes -which increases the frequency of urination. Diuretics and some blood pressure medications can also cause dehydration.
- Illness. Especially in older adults: even minor ailments such as a cold, the flu, bronchitis, or bladder infections can lead to dehydration.
Anyone is at risk of becoming dehydrated but some groups are at greater risk:
Certain medications and chronic illness may increase the risk of dehydration (diabetes, dementia) in senior citizens.
Older people's bodies have less water in them so their water balance can be easily disrupted.
Infections in the lungs or bladder can cause dehydration.
Older persons don't realize that they are dehydrated, and that is because they don't feel thirsty -their sense of thirst is less acute than in younger people. So they should not rely on thirst as a signal to hydrate.
Reduced mobility may also hinder them from drinking water by themselves.
Children and infants
The very young are also at risk. For instance, if they are experiencing diarrhea and⁄or vomiting they will lose fluids very quickly.
Their body surface to volume area is higher than that of an adult so they have more area to lose water through their skin.
Babies cannot communicate that they are thirsty and cannot drink on their own. Be aware of their level of hydration especially during illness or hot weather.
Diabetes, kidney disease, or even a common cold can make you more prone to dehydration. Diuretic medicines that increase urination can also increase the risk of dehydration.
Working or Exercising in Hot or Dry Weather
Hot weather increases fluid loss through evaporation and perspiration, dry conditions are worse than humid ones in terms of water loss. But humid conditions don't let sweat evaporate (and cool the skin) so heat build-up can lead to an increased need for fluids.
People working outdoors or exercising vigorously in hot weather require extra fluids to remain hydrated.
Signs of Dehydration
Be aware of the following signs and symptoms and take note that they are different depending on age:
Dehydration symptoms in adults
See the "Pee" color chart
- Being very thirsty
- Urinating less frequently than usual
- Dark-colored urine (see the "pee" chart)
- Feeling fatigued, tired
- Dry skin
In young children
- Dry Mouth and tongue
- Lack of tears when crying
- No wet diapers for 3 or more hours
- high fever
- Irritability or on the contrary unusually sleepy or drowsy
- Sunken eyes or cheeks
For cases of mild or moderate dehydration, drinking small amounts of water will help the body to restore its fluids. Drink slowly to avoid overloading the stomach with water.
Avoid caffeinated beverages if you don't drink them regularly.
For those who are sweating (i.e. during exercise or work), sports drinks will replenish the lost electrolytes.
Homemade Oral Rehydration Salts (ORS) Recipe
The following recipe for Oral Rehydration Salts comes from (rehydrate.org):
- Six (6) level teaspoons of sugar.
- Half (1 ⁄ 2) a level teaspoon of salt.
- One quart (1 liter) of clean drinking water (or boiled and then cooled water). This is roughly five (5) cups of water.
Mix the salt and sugar in the water until they dissolve.
The salt provides sodium and chlorine ions, the sugar masks the taste of salt and provides energy.
You can also include mashed banana or orange juice which will provide potassium ions to the mixture.
Cases of Severe dehydration need immediate medical attention.
Avoid dehydration by keeping hydrated
Don't wait until your dehydrated: drink plenty of water and eat food with high water content such as fruits and vegetables (they are over 70% water!).
Pay attention to your thirst: drink when you feel thirsty.
If you are vomiting or have diarrhea, start drinking extra water or take an oral rehydration solution.
Start hydrating before you exercise and replenish your fluids at regular intervals during and after you have finished exercising.
If backpacking or trekking outdoors carry plenty of water with you, there are many types of bottles, flasks, and bladders. Depending on the temperature and relative humidity you could need up to 1 quart (1 liter) per hour.
Drink plenty of fluids during hot, dry, or humid weather to replace the fluid lost through sweating.
Dry weather even during winter (cold-dry weather) can also cause dehydration: drink extra water to replenish your fluids.
Older adults should drink more fluids if they are not feeling well because they tend to dehydrate very quickly.
Clear or pale yellow urine is a good sign that you are properly hydrated. See our color chart above.
When to see a doctor
You should call your doctor if you think you or someone in your family may become dehydrated. Do this before the person becomes dehydrated.
Get immediate medical treatment if:
- Diarrhea has gone on for 24 hours or more.
- The person is disoriented, irritable, much sleepier, or less active than usual.
- The person loses consciousness or has confusion or seizures.
- Can't keep fluids down
- The person's fever is over 102°F (38.8°C)
- Heatstroke symptoms appear such as rapid pulse or rapid breathing.
- The person's condition does not improve or worsens despite treatment.
Complications caused by Dehydration
Dehydration can lead to very serious health complications, even frequent episodes of mild dehydration can have nasty consequences (urinary infections, kidney stones, or kidney failure).
The lack of electrolytes alters the body's electric signaling system and can cause seizures, involuntary muscle contractions, and loss of consciousness.
Prolonged exposure to high temperatures combined with dehydration can cause heat cramps, fainting, heat exhaustion, and serious heatstroke, a life-threatening condition.
Keep hydrated. If the weather is hot, dry, or humid, drink more fluids. If you feel thirsty, drink water. If your urine is dark, drink fluids.
The myth of the "8 x 8" rule: learn why it is not true.
References and Further Reading
(1) Taylor K, Jones EB. Adult Dehydration. Updated 2020 Apr 22. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK555956/
Health tips for airline travel, ASMA.
Calista Plummer, Dehydration and You: A 15-Minute Book. Learning Island.
Popkin, Barry M, Kristen E. D'Anci, and Irwin H. Rosenberg. (2010) Water, Hydration and Health. Nutr Rev. v.68 no.8, 439 - 458. doi:10.1111/j.1753-4887.2010.00304.x
About this Article
Dehydration, A. Whittall
©2023 Fit-and-Well.com, 01 Sept. 2023. Update scheduled for 01 Sept. 2025. https://www.fit-and-well.com/health/dehydration.html
Tags: hydration, dehydration, overhydration, water