Dehydration is a condition in which the body loses too much water, usually as a result of excess sweating, vomiting, and/or diarrhea.
Dehydration occurs because more fluid is lost from the body than is taken in. Water is essential for life. Transporting nutrients throughout the body, removing wastes, regulating body temperature, lubrication of joints and membranes, and chemical reactions that occur during cellular metabolism all require water.
The amount of water a person needs to prevent dehydration varies widely depending on the individual's age, weight, level of physical activity, and the environmental temperature. The individual's health and the medications they take may also affect the amount of water a person needs. Most dehydration results from an acute, or sudden, loss of fluids. However, slow-developing chronic dehydration can occur, most often in the frail elderly and in infants and young children, who must rely on others to supply them with liquids.
Healthy people lose water from urination, elimination of solid wastes, sweating, and breathing out water vapor. This water must be replaced through diet. Water makes up about 75% of the body weight of infants, 65% of the weight of children, and 60% of the weight of an adult. In 2004, the United States Institute of Medicine (IOM) recommended that relatively inactive adult men take in about 3.7 liters (about 15 cups) of fluids daily and that women take in about of 2.7 liters (about 10 cups) to replace lost water. These recommendations are for total fluid intake from both beverages and food. Highly active adults and those living in very warm climates need more fluids.
About 80% of the water the average person needs is replaced by drinking liquids. The other 20% is found in food. Below are some foods and the percentage of water that they contain:
Signs of dehydration
General dehydration in adults
Dehydration in children
SOURCE: National Institute of Diabetes and Digestive and Kidney Diseases. “Symptoms & Causes of Diarrhea.” National Institutes of Health, U.S. Department of Health and Human Services. https://www.niddk.nih.gov/health-information/digestive-diseases/diarrhea/symptoms-causes (accessed April 12, 2018).
Dehydration involves more than just water deficiency. Electrolytes are ions that form when salts dissolve in water or body fluids. In order for cells to function correctly, the various electrolytes, such as sodium (Na+) and potassium (K+), must remain within a very narrow range of concentrations. Often electrolytes are lost along with water. For example, sodium is lost in sweat. To prevent the effects of dehydration, both water and electrolytes must be replaced in the correct proportions.
The very young and the very old are most likely to become dehydrated. Young children are at greater risk because they are more likely to get diseases that cause vomiting, diarrhea, and fever. Worldwide, dehydration is the leading cause of death in children. In the United States, 400–500 children under the age of 5 die every year of dehydration. Older people are at risk because they are less likely to drink when they become dehydrated. The thirst mechanism often becomes less sensitive as people age. Also, their kidneys lose the ability to make highly concentrated urine. Older individuals who are confined to wheelchairs or bed and cannot get water for themselves (e.g., nursing home and hospital patients) are at risk of developing chronic dehydration.
Diarrhea, often accompanied by vomiting, is the leading cause of dehydration. Both water and electrolytes are lost in large quantities. Diarrhea is often caused by bacteria, viruses, or parasites. Fever that often accompanies disease accelerates the amount of water that is lost through the skin. The smaller the child, the greater the risk of dehydration. Worldwide, acute diarrhea accounts for the death of about 4 million children each year. In the United States, about 220,000 children are hospitalized for dehydration caused by diarrhea annually.
Heavy sweating also causes dehydration and loss of electrolytes. Athletes, especially endurance athletes, and individuals with active outdoor professions such as roofers and road crew workers are at high risk of becoming dehydrated. Children who play sports can also be vulnerable to dehydration.
Certain chronic illnesses that disrupt fluid balance can cause dehydration. Kidney disease and hormonal disorders, such as diabetes and adrenal gland, or pituitary gland disorders, can cause fluid and electrolyte loss through excessive urination. Disorders such as cystic fibrosis or other genetic disorders resulting in inadequate absorption of nutrients from the intestines can cause chronic diarrhea that leads to dehydration. Individuals with eating disorders who abuse laxatives, diuretics, and enemas or regularly cause themselves to vomit are vulnerable to severe electrolyte imbalances and dehydration. The same is true of people with alcoholism. People who have severe burns over a large part of the body also are likely to become dehydrated because they no longer have skin to act as a barrier to evaporation.
Dehydration can be mild, moderate, or severe. Mild dehydration occurs when fluid losses equal 3%–5%. At this point, the thirst sensation is felt and is often accompanied by dry mouth and thick saliva.
Severe dehydration occurs when fluid losses are 10% or more of body weight. Severe dehydration is a medical emergency for individuals of any age. A loss of fluids equaling 20% of a person's body weight is fatal. Signs of severe dehydration include all those of moderate dehydration as well as lack of sweating, little or no urine production, dry skin that has little elasticity, low blood pressure, rapid heartbeat, fever, delirium, and coma.
Dehydration is diagnosed by physical symptoms. A healthcare professional or observant adult can usually tell by looking at whether they are moderately or severely dehydrated. Blood tests and a urinalysis may be done to check for electrolyte imbalances and to determine if the kidneys are damaged. However, visual signs are enough to begin treatment.
The goal of treatment is to restore fluid and electrolyte balance. For infants and children with mild dehydration, this can be done by giving them oral rehydration solutions such as Pedialyte, Infalyte, Naturalyte, Oralyte, or Rehydralyte. These are available in supermarkets and pharmacies without a prescription. These solutions have the proper balance of salts and sugars to restore the electrolyte balance. Water, apple juice, chicken broth, sodas, and similar fluids are effective in treating mild dehydration. Oral rehydration fluids can be given to young children in small sips as soon as vomiting and diarrhea start. They may continue to vomit and have diarrhea, but some of the fluid will be absorbed. Breastfed infants should continue to nurse on demand. Babies who are formula fed should continue to get their regular formula unless directed otherwise by a pediatrician.
Older children who are dehydrated can be given oral rehydration solutions or sports drinks such as Gatorade for moderate and severe dehydration, otherwise general fluids are fine. Athletes who are dehydrated should be given sports drinks. According to the American College of Sports Medicine, sports drinks are effective in supplying energy for muscles, maintaining blood sugar levels, preventing dehydration, and replacing electrolytes lost in sweat. Adults who are mildly or moderately dehydrated usually improve by drinking water and avoiding coffee, tea, and soft drinks that contain caffeine.
Individuals of all ages who are seriously dehydrated need to be treated by a medical professional. In the case of severe dehydration, the individual may be hospitalized and fluids given intravenously (IV; directly into the vein).
Dehydration is usually an acute condition, and once fluid balance is restored, there are no additional nutritional concerns. In older adults with impaired mobility, the main concern is making sure that they have adequate access to fluids.
Most people recover from dehydration with few complications so long as rehydration fluids are available and treatment begins before the condition becomes severe. However, severe dehydration can be fatal.
See also Atkins diet ; Beverly Hills diet ; Bodybuilding diet ; Caffeine ; Diarrhea diet ; Eating disorders ; Electrolytes ; Food poisoning ; Giardiasis ; Hemorrhoids ; Hoodia ; Hydration ; Juice fasts ; Ketogenic diets ; Metabolism ; Senior nutrition ; Sodium ; South Beach diet ; Sports nutrition ; Water and nutrition .
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American Academy of Pediatrics (AAP), 141 Northwest Point Blvd., Elk Grove Village, IL, 60007, (847) 434-4000, (800) 433-9016, Fax: (847) 434-8000, http://www.aap.org .
American College of Sports Medicine, 401 West Michigan St., Indianapolis, IN, 46202-3233, (317) 637-9200, Fax: (317) 634-7817, http://www.acsm.org .
Tish Davidson, AM