What is Dehydration?
dehydration is a deficit of total body water, with an accompanying disruption of metabolic processes. It occurs when free water loss exceeds free water intake, usually due to exercise, disease, or high environmental temperature. Mild dehydration can also be caused by immersion diuresis, which may increase risk of decompression sickness in divers. Most people can tolerate a three to four percent decrease in total body water without difficulty or adverse health effects. A five to eight percent decrease can cause fatigue and dizziness. Loss of over ten percent of total body water can cause physical and mental deterioration, accompanied by severe thirst. Death occurs at a loss of between fifteen and twenty-five percent of the body water. Mild dehydration is characterized by thirst and general discomfort and is usually resolved with oral rehydration.
What Causes It?
Dehydration occurs because there is too much water lost, not enough water taken in, or most commonly, a combination of the two.
- Diarrhea: Diarrhea is the most common reason for a person to lose excess amounts of water. A significant amount of water can be lost with each bowel movement. Worldwide, more than four million children die each year because of dehydration from diarrhea.
- Vomiting: Vomiting can also be a cause of fluid loss. Not only can an individual lose fluid in the vomitus, but it may be difficult to replace water by drinking because of that same nausea and vomiting.
- Sweat: The body can lose significant amounts of water in the form of sweat when it tries to cool itself. Whether the body temperature is increased because of working or exercising in a hot environment or because a fever is present due to an infection; the body uses water in the form of sweat to cool itself. Depending upon weather conditions, a brisk walk may generate up to 16 ounces of sweat (a pound of water) an hour to allow body cooling, and that water needs to be replaced by the thirst mechanism signaling the person to drink fluids.
- Diabetes: In people with diabetes, elevated blood sugar levels cause sugar to spill into the urine and water then follows, which may cause significant dehydration. For this reason, frequent urination and excessive thirst are among the early symptoms of diabetes.
- Burns: The skin acts as a protective barrier for the body and is also responsible for regulating fluid loss. Burn victims become dehydrated because the damaged skin cannot prevent fluid from seeping out of the body. Other inflammatory diseases of the skin such as toxic epidermal necrolysis, also may be associated with significant fluid loss.
- Inability to drink fluids: The inability to drink adequately is the other potential cause of dehydration, whether it is the lack of availability of water, intense nausea with or without vomiting, or the lack of strength to drink. This coupled with routine or extraordinary water losses can compound the degree of dehydration.
14 signs and symptoms in adults
Your skin loses water by sweating when it’s hot. You also lose moisture through skin in cooler weather because the air is drier. Check your skin for signs of dehydration such as:
- roughness or flaking
- flushing or redness
- cracked skin or lips
- cold or clammy skin
- tightening or shrinking (less plump skin)
Your mouth and tongue may feel dry or sticky when you’re dehydrated. You might also have bad breath.
Your body needs plenty of water to make saliva or spit. When you’re dehydrated, you have less saliva. This causes more bacteria to grow in your mouth. Brushing your teeth and drinking plenty of water helps to get rid of odor-causing bacteria.
You may be able to tell if you’re dehydrated by looking at your urine. Dark yellow to amber urine means you may have mild to severe dehydration. You can usually tell you have healthy hydration levels if your urine is very light in color.
You may also urinate less than normal when dehydrated.
Dehydration can cause or worsen constipation. You may have difficult or fewer bowel movements if you’re not getting enough water. Your stool may look dry or like small lumps.
Water is needed to help digest food and move waste along your digestive tract. Drink plenty of water to stay regular.
5. Thirst and hunger
Thirst is a sign your body needs more water. You may also feel hungrier when you’re dehydrated.
A medical review found that adults who were dehydrated often had a higher body weight. More research is needed on the link between dehydration and hunger. Getting plenty of water may help reduce food cravings. Adults who weigh more also need more water to stay hydrated.
6. Blood pressure
About 55 percent of your blood is liquid. Water loss can lower your blood volume and affect blood pressure.
The American Heart Association lists dehydration as a cause of low blood pressure. Drinking water helps balance blood pressure.
Medical research shows that dehydration can make you feel tired even when you’re rested. Men in a study on dehydration reported they felt fatigue, lethargy, and tiredness. These symptoms may be due to low blood pressure caused by dehydration. Being properly hydrated helps raise energy levels.
You may have a headache even if you’re mildly dehydrated. A study found that women being just 1.36 percentTrusted Source dehydrated triggered headaches.
Headache pain may be linked to low blood pressure due to water loss. Drinking water may help raise blood pressure and ease symptoms.
Dehydration can cause nausea and dizziness. The nausea may lead to vomiting. This makes you lose even more water, worsening symptoms.
Nausea may also be linked to low blood pressure caused by dehydration.
Severe dehydration can lead to fainting. You may feel lightheaded or faint when you stand up suddenly after sitting or lying down. These symptoms may happen when dehydration lowers your blood volume and blood pressure.
11. Heart effects
Dehydration can lead to a pounding heart. A fast heartbeat and quick breathing may be a sign of severe dehydration.
Water loss leads to lower blood volume. This makes the heart work harder to move blood throughout your body. Getting hydrated raises blood volume and returns your heart rate to normal.
12. Brain function
Your brain is more than 70 percent water. Research on men in their 20s found that dehydration slows some types of brain function. It can affect alertness, concentration and memory. Study participants made more mistakes on vision and memory tests when they were dehydrated.
Another study showed that even slight dehydration can cause driving mistakes. This includes drifting across lanes and slowed reaction time while braking. The results found that driving while dehydrated can worsen driving skills as much as if you were at the legal alcohol limit (0.08 percent in the United States), or if you were driving while sleep deprived.
Medical research found that dehydration may make your brain more sensitive to pain. Men in the study showed more pain activity in the brain when they were dehydrated than when they were given plenty of water to drink.
Studies on both men and women found that dehydration made individuals feel anxious, tense, or depressed. Adults reported their mood was lower. Tasks seemed more difficult when they were dehydrated. Mood changes, such as confusion or irritability, are signs of serious dehydration.
Dehydration risk factors
Athletes exposed to direct sun aren’t the only ones at risk for dehydration. In fact, bodybuilders and swimmers are among the athletes who commonly develop the condition, too. Strange as it may seem, it’s possible to sweat in water. Swimmers lose a lot of sweat when swimming.
Some people have a higher risk for developing dehydration than others, including:
- people working outdoors who are exposed to excessive amounts of heat (for example, welders, landscapers, construction workers, and mechanics)
- older adults
- people with chronic conditions
- athletes (especially runners, cyclists, and soccer players)
- infants and young children
- people who reside in high altitudes
Symptoms in babies and toddlers
Babies and toddlers can lose water quickly because of their small size. Signs your baby may be dehydrated include:
- a diaper that’s been dry for three hours or longer
- crying without tears
- unusual sleepiness or drowsiness
- dry mouth
- high fever
Tests for dehydration
The skin elasticity or turgor test can help you determine if you’re dehydrated. To perform the test:
- Gently pinch the skin on your arm or stomach with two fingers so that it makes a “tent” shape.
- Let the skin go.
- Check to see if the skin springs back to its normal position in one to three seconds.
- If the skin is slow to return to normal, you might be dehydrated.
Nail capillary refill test
When your nail bed is pinched, it blanches or whitens. This happens because blood is forced out. Normally, blood returns in two seconds or less. If you’re dehydrated, it may take longer for the area to return to a pink shade. To perform the test:
- Hold the testing hand above your heart.
- Press or pinch your nail bed until it turns white.
- Release the pressure.
- Count how many seconds it takes for color to return to your nail bed.
Dehydration in pregnancy
Drinking plenty of water and fluids is an important part of a healthy pregnancy. During pregnancy, you need more water because your blood volume is higher.
Nausea and vomiting in morning sickness can cause or worsen dehydration. Low levels of amniotic fluids around your baby can happen for many reasons. Drinking more water can help. In some cases, dehydration may trigger early contractions.
Signs of dehydration are similar whether you’re pregnant or not. If you’re pregnant, be sure you’re drinking 8 to 12 glasses of water every day.
How do doctors diagnose dehydration?
Dehydration is often a clinical diagnosis. Aside from diagnosing the reason for dehydration, the health care professional’s examination of the patient will assess the level of dehydration. Initial evaluations may include:
- Mental status tests to evaluate whether the patient is awake, alert, and oriented. Infants and children may appear listless and have whiny cries and decreased muscle tone.
- Vital signs may include postural readings (blood pressure and pulse rate are taken lying down and standing). With dehydration, the pulse rate may increase and the blood pressure may drop because the blood is depleted of fluid. People taking beta blocker medications for high blood pressure, heart disease, or other indications, occasionally lose the ability to increase their heart rate as a compensation mechanism since these medications block the adrenaline receptors in the body.
- Temperature may be measured to assess fever. While it is common to measure temperature in the ear (tympanic) or by mouth (orally), a rectal thermometer may be used to assess core body temperature if the patient appears warm, but no fever is noted tympanically or orally.
- Skin may be checked to see if sweat is present and to assess the degree of elasticity (turgor). As dehydration progresses, the skin loses its water content and becomes less elastic. The amount of sweat is often felt in the armpit or groin, two areas that tend to have moisture normally.
- The mouth can become dry and the health care professional may look at or feel the tongue to see how wet it is.
- Infants may have additional evaluations performed, including checking for a soft spot on the skull (sunken fontanelle), and assessing the suck mechanism, loss of sweat in the armpits and groin, and muscle tone. All are signs of potential significant dehydration.
- Pediatric patients are often weighed during routine child visits, thus a body weight measurement may be helpful in assessing how much water has been lost with the acute illness. This is very rough estimate because all scales are not the same, and for infants and children, it is important to know what clothing they were wearing when the original weight was taken.
Strategies to treat dehydration
Treatments for dehydration include rehydrating methods, electrolyte replacement, and treating diarrhea or vomiting, if needed.
Rehydration by drinking may not be possible for all people, like those who have severe diarrhea or vomiting. In this case, fluids can be given intravenously.
To do this, a small IV tube is inserted in a vein in the arm or hand. It provides a solution that’s often a mix of water and electrolytes.
For those able to drink, drinking water along with an electrolyte-containing rehydration drink, such as a low-sugar sports or electrolyte drink, may be recommended. Children with dehydration are often directed to drink Pedialyte.
Homemade rehydration solution
If an electrolyte drink isn’t available, you can make your own rehydration solution using:
- 1/2 teaspoon salt
- 6 teaspoons sugar
- 1 liter water
Be absolutely certain that you’re using an accurate measurement. Using too much salt or sugar can be dangerous.
Things to avoid
Avoid soda, alcohol, overly sweet drinks, or caffeine. These drinks can worsen dehydration.
Potential complications of untreated dehydration
Untreated dehydration can lead to life-threatening complications, such as:
- heat exhaustion
- heat cramps
- seizures due to electrolyte loss
- low blood volume
- kidney failure
How can I prevent dehydration?
Here are some ways to prevent dehydration:
- If you’re ill, increase your fluid intake, especially if you’re vomiting or having diarrhea. If you can’t keep down liquids, seek medical attention.
- If you’re going to exercise or play sports, drink water before the activity. At regular intervals during the workout, replace your fluids. Make sure to drink water or electrolytes after exercise, too.
- Dress cool in hot months, and avoid being out in direct heat if you can avoid it.
- Even if you aren’t active, drink the recommended amount of fluids.
Dehydration occurs when you’re not getting enough fluids. Whether it’s from exercising, hot weather, or an illness, dehydration can quickly become dangerous — no matter the cause.
You can help prevent dehydration by drinking plenty of water throughout the day and taking electrolytes if you start seeing early signs of fluid loss.
Frequently Asked Questions
How does dehydration occur?
The usual causes of dehydration are a lot of diarrhoea and vomiting. Dehydration can also occur if you do not eat or drink much during an illness or if you do not drink enough during or after strenuous exercise. Medications that cause fluid loss to control excess body fluid (diuretics) are a common long-term cause. Although anyone can become dehydrated, those who become dehydrated the most easily are:
- babies under 1 year old
- the elderly
- anyone who has a fever
- people in hot climates.
What is Dehydration?
The body requires the correct balance of fluid and electrolytes (salts and minerals) to maintain everyday functions and preserve health. Internally, the body has special mechanisms which help to keep this balance in check. However, the loss of fluid and electrolytes through urine, sweat, vomit, diarrhea and other bodily fluids can upset this balance, and in some cases, a person may experience dehydration. The signs and symptoms of mild to moderate dehydration will occur when as little as 2% of the body weight is lost through fluid.
How does dehydration occur?
Dehydration occurs when there is the loss of fluid and electrolytes from the body at a faster rate than they are being replaced. Fluid and electrolyte loss can occur through urine, sweat, vomit and diarrhea.
Does excessive sweating cause dehydration?
The loss of fluid and electrolytes through sweat can lead to dehydration in some circumstances.
When excessive sweating is caused by vigorous or prolonged physical activity (i.e. during endurance sport or exercise), dehydration may occur. This can happen if adequate fluid consumption (with an appropriate hydration fluid) does not occur.
In cases where excessive sweating is due to a fever, there is also a chance of dehydration if adequate hydration is not achieved.
Is it possible to be dehydrated and not realize? If so how (aside from thirst) would you know?
Sometimes we just forget to eat or drink enough, and dehydration can happen without realizing. Often thirst is one of the later symptoms of dehydration to appear. By the time we get thirsty, we can already be moderately dehydrated. Some earlier signs of dehydration are sticky or dryness of the mouth, decreased urine output, and dark yellow colored urine.
Can dehydration cause diarrhea?
Diarrhea is a common cause of moderate dehydration. Dehydration does not itself cause diarrhea.
Why does your head hurt when you are dehydrated?
One of the common symptoms of moderate dehydration is a headache. If you are experiencing a headache, consider whether dehydration could be the cause. If you are experiencing dehydration use a clinical rehydration formula (such as Hydralyte) which will restore the body’s fluid and electrolyte levels and relieve any dehydration present.
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