Dehydration: symptoms, causes, what it feels like

Medically reviewed: 1, February 2024

What is dehydration?

Dehydration is a condition that occurs when the body loses more water than it takes in, resulting in an imbalance of fluids and electrolytes. Dehydration can affect various organs and systems of the body, causing a range of symptoms and complications, some of which can be life-threatening. Dehydration can be caused by various factors.

The person is experiencing symptoms such as sweating, vomiting, and diarrhea, fever, burns, diabetes, kidney disease, alcohol consumption, and inadequate fluid intake. To avoid dehydration, it is important to consume sufficient amounts of fluids, particularly water, and replenishing electrolytes, especially sodium and potassium, when needed.

Loss of water in the body can be diagnosed by measuring the urine output, urine specific gravity, blood pressure, pulse, and skin turgor, as well as by assessing the signs and symptoms of dehydration. This condition can be treated by oral rehydration therapy, intravenous fluid therapy, or other methods, depending on the severity and cause of dehydration.

Dehydration definition

The human body is made up of 70% water. Water is essential to the normal working of the body. It lubricates joints and eyes, aids digestion, flushes out waste and toxins and keeps skin healthy.

Dehydration is when the normal water content of the body is reduced. This leads to a change in the vital balance of chemical substances in the body, especially sodium (salt) and potassium. The function of many cells depends critically on these substances being maintained at the correct levels; serious effects follow any change and dehydration can result in shock, then death.

The risk from dehydration is especially great in babies, infants and older people. It is important that they are treated urgently.

Water loss resulting from an illness such as gastroenteritis can put great strain on an infant because its body is largely made up of water. A newborn baby’s body mass is 80% water and a 12 month old infant’s body mass is 60% water. Depending on the length of the illness and how the infant responds to re-hydration therapy, there should be a successful recovery.

What are the signs of dehydration?

The signs and symptoms of dehydration in adults include:

• thirst;
• low urine output;
• concentrated, dark urine;
• dry, flushed skin;
• dry eyes;
• dry mouth (xerostomia);
• furry tongue;
• headache;
• clammy hands and feet;
• sunken eyes (enophthalmos);
• dizziness; and
• confusion and irritability.

A dehydrated baby may be pale and depressed with sunken eyes. You may also notice a decrease in urine output. If the ‘soft spot’ on your baby’s head is sunken this may be an indication that it is dehydrated. This ‘soft spot’ is called the fontanel and usually closes up by the age of 12-18 months.

Chronic (long term) dehydration is bad for skin, kidneys, liver, joints and muscles and can cause cholesterol problems, headaches, reduced blood pressure (hypotension), fatigue and constipation.

Causes of dehydration

Dehydration is caused by insufficient intake of water or by losing a lot of fluid and not taking in enough to replace it.

It commonly results from an illness with persistent diarrhea and vomiting, as well as excessive sweating from a fever, heavy work in hot surroundings or heatstroke.

Dehydration can also occur as a result of drinking too much alcohol. The headache associated with a hangover indicates that your body is dehydrated. This is why it is important to drink plenty of water when you have been drinking alcohol.

What dehydration can cause?

Dehydration can cause various health problems and complications, depending on the cause and severity of dehydration. Dehydration can cause:

• Hypovolemic shock: This is a life-threatening condition that occurs when the blood volume is too low to maintain adequate blood pressure and blood flow to the vital organs, such as the brain, heart, and kidneys. Hypovolemic shock can cause symptoms such as confusion, dizziness, fainting, cold and clammy skin, rapid and weak pulse, shallow and rapid breathing, and loss of consciousness.
• Acute kidney injury: This grave affliction manifests when the kidneys suffer harm due to insufficient nourishment of blood and oxygen, giving rise to the buildup of deleterious waste substances and toxins within the bloodstream.
• Electrolyte imbalance: Electrolyte imbalance is a perilous state wherein the concentrations of essential electrolytes, including sodium, potassium, calcium, and magnesium, deviate from their optimal levels in the bloodstream, thereby adversely affecting the proper functioning of cells, nerves, muscles, and organs. This condition manifests in a variety of symptoms, such as muscle cramps, weakness, twitching, irregular heartbeat, seizures, coma, and even cardiac arrest.
• Heat stroke, which can severe damage your brain and other organs if not treated in time. The condition can be helped by cooling the body with ice packs, cold water, or evaporative cooling, as well as by intravenous fluids and medication to lower the body temperature and prevent organ damage.

Symptoms of dehydration: What does dehydration feel like?

Dehydration can cause various physical and mental sensations that indicate the body’s need for water and electrolytes. Dehydration can feel like:

• Thirst: triggered by the increase in blood osmolarity and the stimulation of the thirst center in the brain. Thirst is the body’s way of telling you to drink fluids, especially water, to restore the fluid balance and prevent further dehydration.
• Dry mouth and tongue: caused by the decrease in saliva production and the moisture in the mouth and tongue. Dry mouth and tongue can make it difficult to swallow, speak, or taste food, and can increase the risk of dental problems, such as cavities and gum disease.
• Dry skin and eyes: commonly caused by the decrease in skin hydration and elasticity, and the decrease in tear production and lubrication in the eyes. It can make the skin feel tight, rough, or flaky, and can increase the risk of skin infections, irritations, and wrinkles. Eyes can feel itchy, burning, or gritty, and can increase the risk of eye infections, injuries, and vision problems.
• Headache: happens with the decrease in blood volume and pressure, and the increase in blood viscosity and osmolarity, affecting the blood flow and pressure in the brain. Headache can range from mild to severe, and can be located in different parts of the head, depending on the type and severity of dehydration.
• Dizziness and fainting: This is a less common sign of dehydration, it is caused by the decrease in blood pressure and the blood flow to the brain, affecting the balance and consciousness. Dizziness and fainting can occur when standing up quickly from a lying or sitting position, or when performing physical activities, and can increase the risk of falls and injuries.
• Fatigue and weakness: Very common sign of low water level in the body, which is caused by the decrease in energy and the muscle strength, affecting the physical and mental performance. Fatigue and weakness can make you feel tired, sluggish, or lethargic, and can reduce your ability to concentrate, learn, or remember.

What dehydration does to your skin?

Dehydration can have various effects on your skin, which is the largest organ of your body and plays a vital role in protecting you from infections, injuries, and environmental factors. Dehydration can do the following to your skin:

• Reduce the skin hydration and elasticity:

If there is not enough water in the skin cells and the extracellular matrix, which are the structures that support and bind the skin cells together. This can make the skin lose its hydration and elasticity, which are the properties that allow the skin to stretch and bounce back to its normal shape. Dehydration can make the skin feel dry, tight, rough, or flaky, and can increase the risk of skin cracking, peeling, or bleeding.

• Disruption of the skin barrier function and immunity:

Stratum corneum is the outermost layer of the skin that acts as a barrier against water loss, bacteria, viruses, and other foreign substances. Lack of water in this layer can make the skin barrier function and immunity weaker, which are the properties that allow the skin to prevent or fight off infections, inflammations, and allergies. Dehydration can make the skin more prone to skin infections, such as acne, eczema, or impetigo, and can worsen the symptoms of existing skin conditions, such as psoriasis, rosacea, or dermatitis.

• Reduce the skin healing and regeneration:

Lack of enough water content in the dermis, which is the middle layer of the skin that contains the blood vessels, nerves, and fibroblasts, which are the cells that produce collagen and elastin, the proteins that give the skin its strength and flexibility. This can make the skin healing and regeneration slower, which are the properties that allow the skin to repair and renew itself after injuries, wounds, or aging. Dehydration can make the skin more susceptible to scars, bruises, or wrinkles, and can delay the healing of cuts, burns, or ulcers.

Diagnosis

If you experience any of the symptoms outlined you should make an appointment to see your GP as soon as possible. They will carry out a physical examination and may pinch the skin to see if it springs back into place immediately (turgor).

If dehydration is suspected, you may be given a blood or urine test to check the balance of sodium (salt) and potassium in your body.

When dehydration is dangerous?

Dehydration is dangerous when it causes a significant loss of body fluids and electrolytes, leading to hypovolemia, hypotension, shock, and organ failure.

There is too small amount of water in your body, when the urine output is less than 500 ml per day.

To avoid dehydration, it is important to consume sufficient amounts of fluids, particularly water. Severe dehydration can cause the following dangerous complications:

• Hypovolemic shock:

This is a condition that occurs when the blood volume is too low to maintain adequate blood pressure and blood flow to the vital organs, such as the brain, heart, and kidneys. Hypovolemic shock can cause symptoms such as confusion, dizziness, fainting, cold and clammy skin, rapid and weak pulse, shallow and rapid breathing, and loss of consciousness. Hypovolemic shock can be fatal if not treated promptly and aggressively with intravenous fluids and blood transfusions.

• Acute kidney injury:

When you are not taking water for long time, your kidneys get damaged by the lack of blood flow and oxygen, resulting in the accumulation of waste products and toxins in the blood. Acute kidney injury can cause symptoms such as decreased urine output, swelling of the legs and feet, nausea, vomiting, fatigue, and shortness of breath. Acute kidney injury can lead to chronic kidney disease, dialysis, or kidney transplant in severe cases.

Imbalance of electrolytes, that disrubts its composition inside the body. It can be corrected by oral or intravenous rehydration therapy, as well as by medication or supplementation of the deficient or excess electrolytes.

• Heat stroke:

This is a condition that occurs when the body temperature rises above 40°C (104°F) due to the inability of the body to cool itself down by sweating, resulting in damage to the brain and other organs. Heat stroke can usually manifest intself if you feel a strong headache, feeling yourself nausious, want to vomit, feel confusion, agitation, hallucinations, convulsions, and loss of consciousness. Heat stroke can be prevented by avoiding exposure to high temperatures and humidity, wearing loose and light clothing, drinking plenty of fluids, and seeking shade or air conditioning when possible.

Where is a dehydration headache located?

A dehydration headache is a type of headache that is caused by the lack of fluids and electrolytes in the body, affecting the blood flow and pressure in the brain. A dehydration headache can be located in different parts of the head, depending on the type and severity of dehydration. A dehydration headache can be classified into three types:

• Tension-type headache:

This is the most common type of dehydration headache, which is caused by the contraction of the muscles in the neck and scalp, resulting in a dull, aching pain that is felt on both sides of the head, especially in the forehead, temples, and back of the head.

On the other hand, migraine headaches are less common and are caused by the swelling and inflammation of blood vessels in the brain. They cause a pulsating pain on one side of the head, often accompanied by nausea, vomiting, sensitivity to light and sound, and visual disturbances like flashes or zigzag lines.

• Sinus headache:

This is a rare type of headache when dehydrated, which is caused by the inflammation and infection of the sinuses, the air-filled cavities in the skull, resulting in a pressure-like pain that is felt in the forehead, cheeks, nose, and eyes, usually accompanied by nasal congestion, discharge, fever, and cough.

Will dehydration cause high blood pressure?

Dehydration can lead to high blood pressure, or hypertension, which occurs when the pressure of the blood against artery walls becomes too high. This can increase the chances of developing heart disease, stroke, and kidney damage. Dehydration affects various factors that contribute to high blood pressure.

• Blood volume: Dehydration reduces the amount of water in the blood, making it thicker and more concentrated, which increases the resistance and pressure in the blood vessels.
• Blood viscosity: Lack of water in the body increases the concentration of red blood cells, platelets, and proteins in the blood, making it more sticky and viscous, which increases the friction and pressure in the blood vessels.
• Renin-angiotensin-aldosterone system: Dehydration stimulates the release of renin, a hormone that activates the production of angiotensin, a peptide that causes the constriction of the blood vessels, and aldosterone, a hormone that causes the retention of sodium and water in the kidneys, which increases the volume and pressure of the blood.
• Sympathetic nervous system: In this case sympathetic nervous system is activated, which is the part of the nervous system that controls the fight-or-flight response, which increases the heart rate, the force of the heart contraction, and the constriction of the blood vessels, which increases the pressure of the blood.

Will dehydration cause shortness of breath?

Dehydration can cause shortness of breath, also known as dyspnea, which is a condition that occurs when the breathing is difficult, uncomfortable, or inadequate, resulting in a sensation of not getting enough air, and some other factors:

• Blood oxygen level:

Dehydration reduces the amount of water in the blood, which decreases the blood volume and flow, which reduces the oxygen delivery to the tissues and organs, including the lungs. Dehydration leads to higher levels of hemoglobin, the protein responsible for transporting oxygen in red blood cells. This causes a decrease in the ability of hemoglobin to release oxygen, making it more difficult for oxygen to bind and detach from hemoglobin. Additionally, levels of carbon dioxide rise, which is a byproduct of cellular respiration, it lowers the blood pH and increases the acidity, which reduces the oxygen affinity and release, making it harder for the oxygen to bind and unbind from the hemoglobin. Lack of enough water can cause hypoxemia, which is a condition that occurs when the blood oxygen level is too low. This condition leads to symptoms like difficulty breathing and quick, shallow breaths, cyanosis, confusion, and loss of consciousness.

• Lung function:

Dehydration reduces the amount of water in the body, which affects the hydration and elasticity of the lung tissues. An example of a location where gas exchange happens is in the alveoli, which are small air sacs, and the bronchi, the tubes that carry air to and from the lungs. In this severe condition alveoli can collapse, reducing the surface area for gas exchange, and the bronchi to constrict, reducing the airway diameter and increasing the airway resistance. Furthermore, mucus, the sticky fluid that lines the airways and traps dust, bacteria, and other particles, to become thicker and harder to clear, increasing the risk of infection and inflammation. As a result respiratory distress can occur, a condition when the breathing is insufficient to meet the body’s oxygen demand, causing symptoms such as shortness of breath, wheezing, coughing, chest pain, and fatigue.

• Heart function:

The amount of water in the body affects blood pressure and heart rate, which are the main factors that determine how much blood the heart pumps per minute. If someone is dehydrated, their blood pressure can decrease, which means less blood is flowing to the heart. In response, the heart rate may increase to compensate for this decrease in blood flow, leading to a higher demand for oxygen in the heart. Dehydration can also cause the blood to become thicker and more viscous, which increases the resistance and pressure in the blood vessels, and the electrolytes to become imbalanced, which affects the electrical activity and contraction of the heart. It may cause cardiac arrhythmia, a condition characterized by an irregular heartbeat.

Is diarrhea a sign of dehydration?

Diarrhea is a sign of dehydration, as well as a cause of dehydration. Diarrhea is a condition that occurs when the stool is loose, watery, and frequent, resulting in the loss of fluids and electrolytes from the body. Diarrhea can be caused by various factors, such as infections, food poisoning, allergies, medications, irritable bowel syndrome and inflammatory bowel disease are two different conditions affecting the digestive system. Diarrhea can cause dehydration by reducing the absorption of water and electrolytes in the intestines, increasing the secretion of water and electrolytes in the stool, and stimulating the vomiting reflex, which further depletes the body of fluids and electrolytes.

Diarrhea can indicate that the body is dehydrated, as well as worsen the condition and show the following signs:

1. Dry mouth and tongue: Diarrhea reduces the saliva production and the moisture in the mouth and tongue, making them feel dry and sticky.
2. Thirst: Diarrhea increases the thirst sensation, as the body tries to compensate for the fluid loss and maintain the fluid balance.
3. Decreased urine output and dark urine: Diarrhea reduces the urine production and the urine dilution, making the urine output less frequent and the urine color darker and more concentrated.
4. Sunken eyes and cheeks: Diarrhea reduces the fluid volume in the blood vessels and the tissues, making the eyes and cheeks appear sunken and hollow.
5. Skin tenting: Diarrhea reduces the skin elasticity and turgor, making the skin stay lifted or wrinkled when pinched and released, instead of snapping back to its normal position.
6. Dizziness and fainting: Diarrhea reduces the blood pressure and the blood flow to the brain, making the person feel dizzy and faint, especially when standing up quickly.
7. Fatigue and weakness: Diarrhea reduces the energy and the muscle strength, making the person feel tired and weak, especially when performing physical activities.

Will dehydration cause heart palpitations and high heart rate?

Dehydration can cause heart palpitations, which are sensations of the heart beating too fast, too slow, or irregularly. Heart palpitations can be harmless or a sign of a serious heart problem, depending on the cause and severity of the condition. Dehydration can cause heart palpitations by affecting the following factors:

• Blood volume and pressure:

Dehydration reduces the amount of water in the blood, which decreases the blood volume and pressure. Being dehydrated can also make your blood pressure drops when you stand up from lying down or sitting, which can make you feel dizzy, faint, or have a racing heart.

• Blood viscosity and oxygen:

When you’re dehydrated, your blood gets thicker and stickier because there are more red blood cells, platelets, and proteins. This can make it harder for your blood to flow through your vessels, and it also means there’s less oxygen in your blood. As a result, your heart has to pump harder to deliver oxygen to your organs and tissues.

• Electrolyte balance and nerve function:

Dehydration causes the loss of electrolytes from the body, affecting the normal balance and function of the cells, nerves, muscles, and organs. Electrolytes are essential for maintaining the electrical activity and contraction of the heart, as well as the transmission of nerve impulses that regulate the heart rhythm. Dehydration on a long run causes electrolyte inbalance, can cause abnormal heart rhythms, such as atrial fibrillation, ventricular tachycardia, or ventricular fibrillation, causing symptoms such as palpitations, chest pain, shortness of breath, and cardiac arrest.

• Stress and anxiety:

Dehydration can trigger or worsen stress and anxiety, which are emotional and psychological states that can affect the heart and the nervous system. Stress and anxiety can activate the sympathetic nervous system, which is the part of the nervous system that controls the fight-or-flight response, increasing the release of adrenaline and cortisol, which are hormones that increase the heart rate, the force of the heart contraction, and the constriction of the blood vessels, increasing the pressure.

What dehydration does to the brain?

Dehydration can have various effects on your brain, which is the most complex and vital organ of your body and plays a crucial role in controlling your thoughts, emotions, memories, and actions. Dehydration can do the following to your brain:

• Reduce the brain volume and function:

Dehydration decreases the water levels in both brain cells and the cerebrospinal fluid, which is responsible for protecting and supporting the brain and spinal cord. This can make the brain shrink and lose its volume, which can affect its function and performance. Dehydration can make the brain work harder and less efficiently, which can impair your cognitive abilities, such as attention, concentration, learning, memory, reasoning, and problem-solving.

• Reduce the blood flow and oxygen level:

Dehydration leads to a decrease in blood water content, resulting in reduced blood volume and pressure. This causes an increase in blood thickness and concentration, affecting blood flow and pressure in the brain. As a result, the brain may not receive enough oxygen and blood, leading to a condition called hypoxia. Symptoms of hypoxia include headache, dizziness, confusion, lethargy, and even coma.

• Increase the inflammation and oxidative stress:

Dehydration increases the production of cytokines, which are molecules that trigger inflammation, and reactive oxygen species, which are molecules that cause oxidative stress, in the brain. This can make the brain inflamed and oxidized, which can damage its cells and tissues. It can make the brain more vulnerable to neurodegeneration, which is a condition that occurs when the brain cells die or deteriorate, causing symptoms such as memory loss, dementia, Alzheimer’s disease, or Parkinson’s disease.

Dehydration during pregnancy

Dehydration during pregnancy is a common and serious problem that can affect both the mother and the baby. This can occur for various reasons, such as morning sickness, increased urination, sweating, diarrhea, vomiting, fever, or insufficient fluid intake. Such condition may bring various consequences, such as preterm labor, low amniotic fluid, urinary tract infections, constipation, hemorrhoids, or birth defects. But it can be prevented and treated by following some simple tips, such as:

1. Drink plenty of fluids, especially water, throughout the day. Aim for at least eight glasses of water per day, or more if you are exercising, sweating, or experiencing vomiting or diarrhea. You can also drink different types of fluids, such fruit juice, milk or soup, or even herbal tea, but avoid caffeine, alcohol, or sugary drinks, which can dehydrate you more.
2. Eat foods that are rich in water, such as fruits, vegetables, yogurt, or popsicles. These can help you stay hydrated and provide you with vitamins, minerals, and fiber. Avoid foods that are salty, spicy, or fried, which can make you thirsty or cause fluid retention.
3. Monitor your urine color and output. Your urine should be clear or pale yellow, and you should urinate at least every three to four hours. If your urine is dark, cloudy, or foul-smelling, or if you urinate less frequently or in small amounts, you may be dehydrated and need to drink more fluids.
4. Listen to your body and your thirst. If you feel thirsty, dry, or tired, you may be dehydrated and need to drink more fluids. Do not ignore or suppress your thirst, as it is your body’s way of telling you to drink fluids. Drink fluids before, during, and after physical activities, and whenever you feel thirsty.
5. Seek medical attention as soon as possible if you are experiencing signs or symptoms of severe dehydration, such as dizziness, fainting, rapid heartbeat, low blood pressure, confusion, or contractions. It can be dangerous for you and your baby, and may require intravenous fluids and medication to restore your fluid and electrolyte balance.

Dehydration treatment

Dehydration is best treated by fluid intake.

• Drinking water will re-hydrate the body and isotonic drinks will replace lost salt and essential minerals.
• Fluid can also be given by a naso-gastric tube (up the nose) or saline drip (infusion into a vein).

Babies, infants and elderly people need urgent treatment if they are dehydrated.

Prevention

You can avoid dehydration by drinking eight large glasses of water a day and increasing your intake of water if you are ill with sickness and/or diarrhea.

When exercising, you should drink up to one liter of water per hour of exercise, on top of your normal daily amount. This should be increased if you are exercising in warm conditions, as you will dehydrate more quickly.

In hot weather, you will sweat more and lose fluid from your body. Make sure you are drinking enough water to replace lost fluids.