Dehydration occurs when you use or lose more fluid than you take in and your body doesn't have enough water and other fluids to carry out its normal functions. If you don't replace lost fluids, you'll become dehydrated.
Anyone can get dehydrated, but the condition is especially dangerous for young children and older adults.
The most common cause of dehydration in young children is severe diarrhea and vomiting. Older adults naturally have less water in their bodies and may have conditions or take medications that increase their risk of dehydration.
This means that even minor illnesses, such as infections that affect the lungs or bladder, can cause dehydration in older adults.
Dehydration can also occur in any age group if you don't drink enough water during hot weather, especially if you exercise vigorously.
You can usually reverse mild to moderate dehydration by drinking more fluids, but severe dehydration requires immediate medical treatment.
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Thirst is not always a reliable early indicator of the body's need for water. Many people, especially the elderly, don't feel thirsty until they are already dehydrated. That's why it's important to increase your water intake when it's hot or when you're sick.
Dehydration signs and symptoms can also differ according to age.
baby or child
- dry mouth and tongue
- no tears to cry
- No wet diapers for three hours.
- sunken eyes, cheeks
- Sunken soft spot on top of skull
- apathy or irritability
- sed extrema
- less frequent urination
- dark colored urine
When to see a doctor
Call your GP if you or a loved one:
- You have had diarrhea for 24 hours or more.
- Is irritable or disoriented and much sleepier or less active than usual
- I can't keep the fluids down
- Have bloody or black stools
Request an appointment at the Mayo Clinic
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Sometimes dehydration occurs for simple reasons: you don't drink enough because you're sick or busy, or you don't have access to clean water when traveling, hiking, or camping.
Other causes of dehydration include:
- Diarrhea, vomiting.Acute and severe diarrhea, that is, diarrhea that comes on suddenly and violently, can cause an enormous loss of water and electrolytes in a short period of time. If you have vomiting along with the diarrhea, you will lose even more fluids and minerals.
- Fever.In general, the higher the fever, the more dehydrated you will be. The problem gets worse if you have a fever in addition to diarrhea and vomiting.
- excessive sweatYou lose water when you sweat. If you engage in vigorous activity and don't replace fluids during exercise, you could become dehydrated. Hot, humid weather increases the amount of sweat and the amount of fluid you lose.
- Increased urination.This could be due to undiagnosed or uncontrolled diabetes. Certain medications, such as diuretics and some blood pressure medications, can also cause dehydration, often causing you to urinate more.
Anyone can become dehydrated, but some people are more at risk:
- Infants and children.The group most likely to experience severe diarrhea and vomiting, infants and children, are especially vulnerable to dehydration. Because they have a greater surface area than volume area, they also lose a greater proportion of their fluids due to high fevers or burns. Young children are often unable to tell that they are thirsty, nor can they drink on their own.
- Older adults.As you age, your body's fluid reserve decreases, your ability to conserve water decreases, and your sense of thirst becomes less acute. These problems are exacerbated by chronic illnesses, such as diabetes and dementia, and the use of certain medications. Older adults may also have mobility issues that limit their ability to get water for themselves.
- People with chronic illnesses.Having uncontrolled or untreated diabetes puts you at high risk for dehydration. Kidney disease also increases the risk, as do drugs that increase urination. Even a cold or sore throat makes you more susceptible to dehydration because you're less likely to feel like eating or drinking when you're sick.
- People who work or exercise outdoors.When it's hot and humid, your risk of dehydration and heat illness increases. This is because when the air is humid, sweat cannot evaporate and cool you down as quickly as it normally would, and this can lead to an increase in body temperature and a need for more fluids.
Dehydration can lead to serious complications, including:
- heat injury.If you don't drink enough fluids when you exercise vigorously and you sweat a lot, you can end up with a heat injury, which ranges in severity from mild heat cramps to life-threatening heat exhaustion or heatstroke.
- Urinary and kidney problems.Prolonged or repeated bouts of dehydration can lead to urinary tract infections, kidney stones and even kidney failure.
- Convulsions.Electrolytes, such as potassium and sodium, help carry electrical signals from one cell to another. If your electrolytes are out of balance, normal electrical messages can be confused, which can lead to involuntary muscle contractions and sometimes unconsciousness.
- Shock due to low blood volume (hypovolemic shock).This is one of the most serious and sometimes fatal complications of dehydration. It occurs when low blood volume causes a drop in blood pressure and a drop in the amount of oxygen in your body.
To avoid dehydration, drink plenty of fluids and eat foods rich in water, such as fruits and vegetables. Letting thirst be your guide is an adequate daily pattern for most healthy people.
People may need to drink more fluids if they have conditions such as:
- Vomiting or diarrhea.If your child is vomiting or has diarrhea, start giving more water or oral rehydration solution at the first signs of illness. Do not wait until dehydration occurs.
- tiring exercise.In general, it's best to start hydrating the day before strenuous exercise. Producing a lot of clear, dilute urine is a good indication that you're well hydrated. During activity, replenish fluids at regular intervals and continue to drink water or other liquids after you finish.
- Warm or cold climate.You need to drink extra water in hot or humid weather to help lower your body temperature and replace what you lose through sweat. You may also need additional water in cold climates to combat moisture loss from dry air, particularly at higher altitudes.
- Illness.Older adults are more often dehydrated during minor illnesses such as the flu, bronchitis or bladder infections. Make sure you drink more fluids when you don't feel well.
By the staff at the Mayo Clinic
October 14, 2021
Dehydration is caused by not drinking enough fluid or by losing more fluid than you take in. Fluid is lost through sweat, tears, vomiting, urine or diarrhoea. The severity of dehydration can depend on a number of factors, such as climate, level of physical activity and diet.What are 3 warning signs of dehydration? ›
feeling thirsty. dark yellow, strong-smelling pee. peeing less often than usual. feeling dizzy or lightheaded.What problems can dehydration cause? ›
Symptoms can include thirst, dry mouth, and less urine. Mild dehydration can cause problems with blood pressure, heart rate, and body temperature. Severe dehydration can also cause weakness or confusion. In extreme cases, it can lead to kidney damage, brain damage and even death.What is the fastest way to rehydrate? ›
Water. While it likely comes as no surprise, drinking water is most often the best and cheapest way to stay hydrated and rehydrate. Unlike many other beverages, water contains no added sugars or calories, making it ideal to drink throughout the day or specifically when you need to rehydrate, such as after a workout.How can I rehydrate fast? ›
The fastest way to hydrate is with an oral rehydration solution. These products are packed with electrolytes which are minerals found in your body that balance fluid levels and maintain optimal hydration. While you can hydrate fast with regular water, focus on electrolytes.What deficiency causes dehydration? ›
Dehydration happens when you don't drink enough water, or when you lose water quickly through, for example, sweating, vomiting and/or diarrhea. Certain medications such as diuretics (water pills) can result in increased urination and dehydration.When should you go to the ER for dehydration? ›
The person loses consciousness at any time. There is any other change in the person's alertness (for example, confusion or seizures). The person has a fever over 102°F (38.8°C). You notice symptoms of heatstroke (such as rapid pulse or rapid breathing).How do you test if you are dehydrated? ›
She further said, “Here is an easy way to figure out if your body needs more water. Take the skin on your knuckles and pinch it. If the skin goes down easily, then you are hydrated. If it takes a long time to go down, clearly you are dehydrated.How do I know if my dehydration is serious? ›
Not Urinating or Very Dark Urine
Normal urine should be pale yellow, like lemonade. If your urine is a darker color, similar to apple juice, this could be a sign of moderate to severe dehydration. If you're not urinating at all, you're most likely severely dehydrated. This requires immediate medical attention.
- Not peeing or having very dark yellow pee.
- Very dry skin.
- Feeling dizzy.
- Rapid heartbeat.
- Rapid breathing.
- Sunken eyes.
- Sleepiness, lack of energy, confusion or irritability.
So, what if you drink loads of water each day but are still feeling thirsty and dehydrated? It can be a sign that something else is going on. Factors like your medication, how much you sweat and if you're sick can affect your levels of hydration.What organs are affected by dehydration? ›
The skin, muscles, kidneys, brain, and heart can all suffer from the effects of dehydration.What organ can cause dehydration? ›
This is when the kidneys go to work harder than it should, and when not attended to properly, it can cause dehydration. In addition, when the kidneys do not get enough sodium and other fluids, they begin to reduce the amount of urine produced to compensate for this lack.
Water is your best bet for everyday hydration, since it is free of sugar, calories, and caffeine. All of your daily food and beverages contribute to your daily fluid needs.What hydrates faster than water? ›
Research shows that milk is one of the best beverages for hydration, even better than water or sports drinks. Researchers credit milk's natural electrolytes, carbohydrates, and protein for its effectiveness.How much water do I need to drink to get rehydrated? ›
2. During work or exercise in the heat: • Drink 8-12 ounces of fluid every 15 minutes. Drinking more than 1.5 liters per hour is not recommended and may increase the risk for developing hyponatremia (low sodium).What's the best thing to drink when you're dehydrated? ›
Water is your best bet for everyday hydration, since it is free of sugar, calories, and caffeine. All of your daily food and beverages contribute to your daily fluid needs.What to eat when dehydrated? ›
Cantaloupe, grapefruit, strawberries, watermelon, broccoli, cabbage, cauliflower, celery, cucumbers, eggplant, lettuce, sweet peppers, radishes, spinach, zucchini, and tomatoes are all at least 90% water. Soups, popsicles, water ice, and gelatins are also high in water.