Vomiting, diarrhea, excessive sweating, burns, kidney failure, and use of diuretics may cause dehydration.
People feel thirsty, and as dehydration worsens, they may sweat less and excrete less urine.
If dehydration is severe, people may be confused or feel light-headed.
Treatment is restoring lost water and mineral salts (such as sodium and potassium) that are dissolved in the blood (electrolytes), usually by drinking but sometimes with intravenous fluids.
(See also About Body Water About Body Water Water accounts for about one half to two thirds of an average person’s weight. Fat tissue has a lower percentage of water than lean tissue and women tend to have more fat, so the percentage... read more .)
Dehydration occurs when the body loses more water than it takes in. Vomiting Nausea and Vomiting in Adults Nausea is an unpleasant feeling of needing to vomit. People also may feel dizziness, vague discomfort in the abdomen, and an unwillingness to eat. Vomiting is a forceful contraction of the stomach... read more , diarrhea Diarrhea in Adults Diarrhea is an increase in the volume, wateriness, or frequency of bowel movements. (See also Diarrhea in Children.) The frequency of bowel movements alone is not the defining feature of diarrhea... read more , the use of drugs that increase urine excretion (diuretics), profuse sweating (for example, during heat waves, particularly with prolonged exertion), and decreased water intake can lead to dehydration.
Dehydration is particularly common among older people because their thirst center may not function as well as that in younger people. Therefore, some older people may not recognize that they are becoming dehydrated. Certain disorders such as diabetes mellitus Diabetes Mellitus (DM) Diabetes mellitus is a disorder in which the body does not produce enough or respond normally to insulin, causing blood sugar (glucose) levels to be abnormally high. Urination and thirst are... read more , diabetes insipidus Central Diabetes Insipidus Central diabetes insipidus is a lack of the hormone vasopressin (antidiuretic hormone) that causes excessive production of very dilute urine (polyuria). Central diabetes insipidus has several... read more , and Addison disease Addison Disease In Addison disease, the adrenal glands are underactive, resulting in a deficiency of adrenal hormones. Addison disease may be caused by an autoimmune reaction, cancer, an infection, or some... read more 
can increase the excretion of urine and thereby lead to dehydration.
Dehydration in infants and children Dehydration in Children Dehydration is loss of water from the body, usually caused by vomiting and/or diarrhea. Dehydration occurs when there is significant loss of body water and, to varying amounts, electrolytes... read more is also common because the amount of fluid lost during diarrhea or vomiting may represent a larger proportion of their body fluids than in older children and adults.
Symptoms of Dehydration
At first, dehydration stimulates the thirst center of the brain, causing thirst, a powerful motivator for people to drink more fluids. If water intake does not keep up with water loss, dehydration becomes more severe. Sweating decreases, and less urine is excreted. Water moves from inside the cells to the bloodstream to maintain the needed amount of blood (blood volume) and blood pressure (see About Body Water About Body Water Water accounts for about one half to two thirds of an average person’s weight. Fat tissue has a lower percentage of water than lean tissue and women tend to have more fat, so the percentage... read more ). If dehydration continues, tissues of the body begin to dry out, and cells begin to shrivel and malfunction.
Symptoms of mild to moderate dehydration include
Thirst
Reduced sweating
Reduced skin elasticity
Reduced urine production
Dry mouth
In severe dehydration, the sensation of thirst may actually decrease and blood pressure can fall, causing light-headedness or fainting, particularly upon standing (a condition called orthostatic hypotension Dizziness or Light-Headedness When Standing Up In some people, particularly older people, blood pressure drops excessively when they sit or stand up (a condition called orthostatic or postural hypotension). Symptoms of faintness, light-headedness... read more ). If dehydration continues, shock Shock Shock is a life-threatening condition in which blood flow to the organs is low, decreasing delivery of oxygen and thus causing organ damage and sometimes death. Blood pressure is usually low... read more and severe damage to internal organs, such as the kidneys, liver, and brain, occur. Brain cells are particularly susceptible to more severe levels of dehydration. Consequently, confusion is one of the best indicators that dehydration has become severe. Very severe dehydration can lead to coma.
Spotlight on Aging: Water Balance
Dehydration Older people are particularly susceptible to dehydration. In older people, common causes of dehydration include
Additionally, older people sense thirst more slowly and less intensely than younger people do, so even those who are otherwise well may not drink enough fluids for a variety of reasons, including incontinence Urinary Incontinence in Adults Urinary incontinence is involuntary loss of urine. Incontinence can occur in both men and women at any age, but it is more common among women and older people, affecting about 30% of older women... read more Older people have a higher percentage of body fat. Because fat tissue contains less water than lean tissue, the total amount of water in the body tends to decrease with age. Overhydration In overhydration Overhydration Overhydration is an excess of water in the body. People can develop overhydration if they have a disorder that decreases the body’s ability to excrete water or increases the body's tendency... read more , the body contains too much water. In older people, the kidneys excrete excess water less efficiently, and thus older people can develop overhydration more easily than younger people do. Swelling may or may not occur. |
Diagnosis of Dehydration
A doctor's evaluation
Sometimes blood tests
Dehydration can often be diagnosed from symptoms and the results of a doctor's examination. But sometimes doctors do blood tests for people who appear seriously ill or who take certain drugs or have certain disorders.
Dehydration normally causes the sodium level in the blood to increase. The reason is that although the common causes of dehydration (such as profuse sweating Excessive Sweating People with excessive sweating (hyperhidrosis) sweat profusely, and some sweat almost constantly. Excessive sweating usually has no clear cause but is sometimes caused by infections, metabolic... read more , vomiting Nausea and Vomiting in Adults Nausea is an unpleasant feeling of needing to vomit. People also may feel dizziness, vague discomfort in the abdomen, and an unwillingness to eat. Vomiting is a forceful contraction of the stomach... read more , and diarrhea Diarrhea in Adults Diarrhea is an increase in the volume, wateriness, or frequency of bowel movements. (See also Diarrhea in Children.) The frequency of bowel movements alone is not the defining feature of diarrhea... read more ) result in a loss of electrolytes Overview of Electrolytes Well over half of the body's weight is made up of water. Doctors think about the body's water as being restricted to various spaces, called fluid compartments. The three main compartments are... read more (especially sodium and potassium), even more water is lost, so the concentration of sodium in the blood rises.
Prevention of Dehydration
Prevention of dehydration is better than cure. Adults should drink at least 6 glasses of fluids daily (including fluid from eating foods high in water content, such as fruits and vegetables). Fluid intake should be increased on hot days, during or after prolonged exercise, and, if possible, when people have vomiting and/or diarrhea.
Exercise, a high body temperature, and hot weather increase the body’s need for water. Flavored sports drinks have been formulated to replace electrolytes lost during vigorous exercise. These drinks can be used to prevent dehydration. People should drink fluids with electrolytes before and during exercise as well as afterward. Before exercising, people with heart or kidney disorders should consult their doctors about how to safely replace fluids.
Treatment of Dehydration
Replacing fluids and electrolytes
For treating mild dehydration, drinking plenty of water may be all that is needed. With moderate and severe dehydration, lost electrolytes (especially sodium and potassium) must also be replaced.
Oral rehydration solutions Treatment Dehydration is loss of water from the body, usually caused by vomiting and/or diarrhea. Dehydration occurs when there is significant loss of body water and, to varying amounts, electrolytes... read more that contain appropriate amounts of electrolytes are available without a prescription. These solutions work well to treat dehydration, especially that caused by vomiting or diarrhea in children. Sports drinks do not necessarily contain enough electrolytes to be an adequate substitute for these solutions. However, when a person is vomiting, drinking fluids may not be sufficient to treat dehydration.
More severe dehydration requires treatment by doctors with intravenous solutions containing sodium chloride. The intravenous solution is given rapidly at first and then more slowly as the physical condition improves.
Treatment is also directed at the cause of dehydration. For example, when people have nausea and vomiting Nausea and Vomiting in Adults Nausea is an unpleasant feeling of needing to vomit. People also may feel dizziness, vague discomfort in the abdomen, and an unwillingness to eat. Vomiting is a forceful contraction of the stomach... read more or diarrhea Diarrhea in Adults Diarrhea is an increase in the volume, wateriness, or frequency of bowel movements. (See also Diarrhea in Children.) The frequency of bowel movements alone is not the defining feature of diarrhea... read more , drugs to control or stop the vomiting or diarrhea may be used.
FAQs for Dehydration
What is dehydration?
Dehydration is when there isn't enough water in the body.
What are the signs of dehydration?
With mild dehydration, people feel thirsty and their mouth is dry. With severe dehydration, people get light-headed, confused, and dizzy when they stand up. Without treatment, people eventually go into a coma and die.
Can dehydration cause fever?
No, dehydration does not cause fever, although many disorders that cause fever can also lead to dehydration.
What causes dehydration?
Dehydration is caused when people lose more body water than they take in. So it can be caused by disorders or problems that make people lose fluid, such as gastroenteritis Overview of Gastroenteritis Gastroenteritis is inflammation of the lining of the stomach and small and large intestines. It is usually caused by infection with a microorganism but can also be caused by ingestion of chemical... read more 
with vomiting and diarrhea, sweating profusely in hot weather Overview of Heat Disorders Humans, who are warm-blooded animals, maintain their body temperature within 1 or 2 degrees of 98.6° F (37° C) as measured by mouth and 100.4° F (38° C) as measured rectally, despite large fluctuations... read more , and uncontrolled diabetes Diabetes Mellitus (DM) Diabetes mellitus is a disorder in which the body does not produce enough or respond normally to insulin, causing blood sugar (glucose) levels to be abnormally high. Urination and thirst are... read more . And dehydration can occur when people can't get enough water to drink, such as stranded travelers or older disabled people living alone.
Can dehydration cause diarrhea?
No, it's the other way around. Diarrhea can cause dehydration.
What do you do for dehydration?
For mild dehydration, drinking extra water may be all that is needed. For more severe dehydration, people should drink a special oral rehydration solution that contains the right concentration of minerals (electrolytes) and sugar. Juice, soda, and sports drinks are not as effective. For severe dehydration, doctors give people fluid through an IV.
Can dehydration cause urinary tract infection (UTI)?
How do you test for dehydration?
Doctors can often diagnose dehydration without tests, but sometimes they measure the concentration of sodium and other electrolytes in the blood and test how concentrated the person's urine is.
How long does it take to recover from dehydration?
If the problem that caused dehydration is resolved and the person gets the right amount of fluid, mild to moderate dehydration can resolve in less than a day. Severe dehydration or dehydration of long duration should be treated by doctors in a hospital and typically takes 2 to 3 days to resolve with proper treatment.
How do you prevent dehydration?
To prevent dehydration, people should drink more fluid when they are working or exercising in hot weather. People should make sure that older family members have access to plenty of water when they are alone in a hot building or place. People who are not doing strenuous activity or are not in a hot environment do not need to force themselves to drink extra water when they're not thirsty.
