Dehydration

Dehydration is when the body loses more water than it gets. This can happen because of sweating a lot, health issues, or not drinking enough water. Even long dives underwater, called immersion diuresis, can make divers more likely to get sick.

Most people can lose a little water — about 3 to 4% of their total body water — and not feel too bad. But losing 5 to 8% can make someone feel tired and dizzy. Losing more than 10% can make the body and mind not work well, and a person will feel very thirsty. Losing too much water — about 15 to 25% — can be very dangerous.

Dehydration can also cause hypernatremia, which means there is too much sodium in the blood. Over time, not drinking enough water can help kidney stones form or cause long-term problems with the kidneys. Usually, drinking water or special drinks called oral rehydration solutions can help with mild dehydration. In serious cases, doctors might need to give fluids directly into the blood.

Signs and symptoms

When the body loses too much water, you might feel very thirsty and get headaches. Other signs include feeling tired, having no appetite, and peeing less. As dehydration gets worse, you might feel confused. Even a small loss of water can make it harder to think clearly. Older people may not feel as thirsty when they’re dehydrated, but they can still get tired and weak, especially in hot weather.

Cause

Dehydration happens when the body loses more water than it takes in. This can occur during hot weather, at high altitudes, or while doing long sports activities. Elderly people, young children, and those with chronic illnesses are especially at risk.

Medications can also cause dehydration as a side effect. Water leaves the body through sweating, vomiting, diarrhea, and other natural processes. Diseases that affect how the body manages water and sodium can also lead to dehydration.

Mechanism

The human body is made up of a lot of water, from about 70–75% in newborns to less in adults. This water is found inside cells or outside cells, which includes blood.

When the body loses too much water, the brain detects this change and signals the release of a hormone called antidiuretic hormone (ADH). ADH helps the body hold onto water by increasing water absorption in the kidneys and narrowing blood vessels to keep blood pressure stable.

Diagnosis

Dehydration happens when the body loses more water than it takes in. This can occur during normal activities like breathing, urination, perspiration, diarrhea, or vomiting.

If dehydration becomes severe, it can be dangerous and cause health problems.

Doctors check for signs of dehydration by looking at the skin and other parts of the body. They might see dry mouth, dry underarms, slow return of pinched skin to its normal shape, and sunken eyes. In serious cases, people might feel dizzy or weak. Blood and urine tests can also help show if someone is dehydrated.

Prevention

Feeling thirsty is a sign that you need to drink more water. How much water you need depends on your size, how active you are, your age, and the weather.

When you exercise or are in a hot place, you might need to drink more water.

When it's hot or humid, or if you're working out hard, you lose water through sweating. This can also make you lose important minerals like sodium. For most people, drinking water when you're thirsty is enough to stay safe. Sports drinks with a little sodium can help, but plain water is usually all you need.

Treatment

Main article: Management of dehydration

"Rehydrated" redirects here. For the SpongeBob video game remaster, see SpongeBob SquarePants: Battle for Bikini Bottom – Rehydrated.

The best way to treat mild dehydration is to drink water and stop losing fluids. Drinking water helps restore the fluid in your blood. Eating food also helps because food gives us water. As you drink, your urine will return to normal.

In some cases, you might need to drink special solutions with water and important minerals called electrolytes. For mild dehydration, these solutions are usually easy to drink and don’t need special equipment. For more serious cases where someone can’t drink or feels very weak, doctors might give fluids directly into a vein, but this is done safely in a medical setting.

Prognosis

The outlook for dehydration depends on what caused it and how severe it is. For mild dehydration, drinking water usually fixes the problem. Long-term dehydration, like from hard physical work or not feeling thirsty often enough, can affect kidney health. Older people who become dehydrated may face confusion, infections, falls, and slower healing of wounds. For children with mild to moderate dehydration, drinking fluids is enough to help them fully recover.

Main article: chronic kidney disease