Medically Reviewed By William C. Lloyd III, MD, FACS

What is dehydration?

Dehydration is an abnormal condition in which the body's cells are deprived of an adequate amount of water. Water makes up about 70% of the muscles, organs and tissues in the body and is crucial to many of the body's processes.

Dehydration negatively affects important bodily functions, including toxin elimination, delivery of nutrients and oxygen to the cells of the body, energy production, and joint lubrication. Severe dehydration affects every body system and can also impact the proper balance of vital electrolytes. Sodium and potassium are electrolytes essential to healthy functioning of the body and critical processes, such as muscle function and a normal heart rhythm. Complications of severe dehydration can be serious and life threatening and include shock, coma and death.

Dehydration is categorized as mild, moderate or severe, based on the extent of the body’s fluid loss. Moderate and severe dehydration can be a life-threatening emergency. Infants, children, athletes and the elderly are particularly prone to dehydration and severe complications, although dehydration can occur in any age group or population.

Dehydration can be due to conditions that cause the body to lose too much water, such as excessive heat, sweating, low humidity, bleeding, alcohol intoxication, medication side effects, and high elevation. Dehydration can also be caused by not drinking enough water and fluids. Dehydration is also a symptom of a wide variety of underlying diseases, disorders and conditions, such as gastroenteritis (stomach flu), aldosterone deficiency, and type 1 diabetes.

Moderate to severe dehydration can be serious and life threatening, as well as a symptom of a serious disease or condition. Seek immediate medical care (call 911) if you, or someone you are with, have serious symptoms of dehydration, such as not urinating or urinating only very small amounts of dark-colored urine; weakness and dizziness; a change in consciousness or alertness; or severe, persistent diarrhea or vomiting.

What are the symptoms of dehydration?

Symptoms of dehydration vary between individuals depending on the underlying cause. Dehydration symptoms can be acute and appear relatively suddenly, such as during or after an illness involving repeated vomiting and diarrhea. Dehydration can also be ongoing and chronic, such as when a person does not drink enough fluids because of a fear of incontinence (loss of bladder control).

Some people, especially the elderly, may be unaware that they have symptoms of dehydration because they may not notice the symptoms or may attribute the symptoms to other conditions and factors, such as migraine headache or dry winter weather.

Symptoms of dehydration include:

Serious symptoms that might indicate a life-threatening condition

Moderate to severe dehydration can be serious and life threatening without a swift diagnosis and treatment. Dehydration can also be a symptom of very serious underlying conditions, such as type 1 diabetes or kidney failure. Seek immediate medical care (call 911) if you, or someone you are with, have any of the following symptoms or a combination of these symptoms:

  • Change in consciousness or alertness, such as unresponsiveness and lethargy

  • Chest pain or discomfort, or palpitations

  • Confusion

  • Dizziness

  • Inability of an infant to feed and respond normally

  • Lack of tears, especially in a crying infant

  • Muscle cramps and weakness

  • Nausea and vomiting

  • Not urinating or urine that is very dark yellow, brown, or tea colored

  • Seizure

  • Sunken eyes

  • Sunken fontanel (an infant’s soft spot on the top of the head)

  • Weak or limp body posture in an infant

What causes dehydration?

Dehydration can be caused by not drinking enough water and fluids. Dehydration can also be the result of conditions that cause the body to lose too much water, such as excessive diarrhea, serious burns, fever, and high elevation. Dehydration is a symptom of a wide variety of underlying diseases, disorders and conditions, such as aldosterone deficiency, type 1 diabetes, and kidney failure.

Common conditions that cause dehydration

Dehydration can be caused by not drinking enough fluids to replace those lost through everyday activities and normal body functions, such as the moisture lost through breathing, urinating and sweating. Fluids can also be lost through everyday habits and environmental conditions including:

  • Alcohol consumption or intoxication

  • Excessive heat, which can lead to heat exhaustion and heat stroke

  • Exercise and sports that cause excessive perspiration, such as hockey, marathon races, and soccer

  • Hemorrhage (bleeding)

  • High elevation

  • Low humidity

Conditions involving excessive urination that cause dehydration

Conditions that cause the body to lose too much fluid through excessive urination include:

Conditions involving vomiting, diarrhea and fever that cause dehydration

Many conditions can lead to dehydration through vomiting and diarrhea with or without fever. Some common conditions include:

What are the risk factors for dehydration?

Health care professionals have identified certain risk factors that can make you more prone to dehydration. Risk factors include:

  • Advanced age (older than 65)

  • Diabetes

  • Diarrhea, fever or vomiting

  • Disease, disorder or condition that involves excessive urine output such as diabetes

  • Recreational drug use (cocaine, meth, ecstasy)

  • Young age (generally six years and younger)

Reducing your risk of dehydration

An adequate amount of water, or good hydration, is necessary to prevent dehydration. In an otherwise healthy person, dehydration can be prevented by drinking about eight 8-ounce glasses of water per day. If you have a disease, disorder or condition that causes you to lose too much water, you can best lower your risk of dehydration by seeking regular medical care and following the treatment plan you and your health care professional design specifically for you.

How is dehydration treated?

The first step in treating dehydration is prevention. For healthy adults, this includes drinking eight 8-ounce glasses of water every day. Water needs will be greater for certain people, such as athletes or people who live at high altitudes or in hot, dry climates. Athletes may benefit from drinking a solution, such as Gatorade, that is fortified with the electrolytes that are lost through sweating.

Once dehydration develops, prompt recognition and treatment generally results in a good outcome and minimizes the chances of developing serious complications. Treatment generally involves a multifaceted plan that addresses the underlying or associated cause, such as vomiting or athletic overtraining, while safely rehydrating the patient. Treatment plans are individualized depending on the cause, the presence of other diseases, your age, and other factors.

Treatment of mild dehydration

Mild dehydration can often be cured by drinking fluids in small amounts at frequent intervals. For infants and children who have vomiting or diarrhea, an oral rehydrating solution, such as Pedialyte, is often recommended at the onset of vomiting or diarrhea. Any drink or fluid that contains caffeine, such as coffee or soda, should be avoided. Caffeine can make dehydration worse by causing the body to lose more water, resulting in increased urination.

Treatment of moderate to severe dehydration

Moderate to severe dehydration generally requires hospitalization and in some cases, intensive care. Intravenous fluids are administered and electrolyte replacement may also be necessary. Electrolytes and other important parameters, such as vital signs, are frequently or continuously monitored. For life-threatening cases that include such complications as kidney failure and hypovolemic shock, life-support measures may be necessary.

What are the possible complications of dehydration?

Complications associated with dehydration can be progressive and vary depending on the underlying cause. Because dehydration can be due to serious diseases, failure to seek treatment can result in serious complications and permanent damage. It is important to contact your health care provider when you experience moderate to severe dehydration. Once the underlying cause is diagnosed, it is important to follow the treatment plan you and your health care practitioner design specifically for you to lower your risk of potential complications including:

  • Brain damage

  • Cardiac arrhythmias (abnormal heart rhythms)

  • Coma

  • Electrolyte imbalances

  • Kidney failure

  • Seizure

  • Shock

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    1. Dehydration. Medline Plus, a service of the National Library of Medicine National Institutes of Health.
    2. Dehydration. PubMed Health, a service of the NLM from the NIH.
    3. What is Dehydration?
    4. Tierney LM Jr., Saint S, Whooley MA (Eds.) Current Essentials of Medicine (4th ed.). New York: McGraw-Hill, 2011
    Medical Reviewer: William C. Lloyd III, MD, FACS
    Last Review Date: 2020 Nov 2
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    THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.