Dehydration occurs when you lose more fluid than you take in, and your body doesn't have enough water and other fluids to carry out its normal functions. Young children, older adults, the ill and chronically ill are especially susceptible. Water is excreted from the body in many different forms: through urine and stool, sweating, and breathing (exhaling CO2). Dehydration symptoms generally become noticeable after 2% of one's normal water volume has been lost.[1]

Adequate hydration plays a key role in maintaining:[2]

  • Circulation
  • Lubrication
  • Body temperature
  • Lymphatic system
  • Removal of waste products from the body and cells
  • Facilitating ingestion and digestion
  • Flushing out the urinary tract, eyes, and other organs

You can usually reverse mild to moderate dehydration by drinking more fluids, but severe dehydration needs immediate medical treatment. [3] 

There are three main types of dehydration: hypotonic (primarily a loss of electrolytes), hypertonic (primarily loss of water), and isotonic (equal loss of water and electrolytes).  The most commonly seen in humans is isotonic. [4]


Dehydration is most commonly found in the elderly, infants, people with fever, athletes, people living in high altitudes, and the chronically ill.  Children are most affected in the first two years of their life and 2.2 million will die in this year around the world.[1] 

The elderly have an altered sense of thirst perception, changes in body water composition, and a decline in renal function as they age. Dehydration was diagnosed in 6.7% of hospitalized geriatric patients in the year 2007.  In 50% of febrile cases, the patients were dehydrated and the mortality rate exceeds 50% in some studies.[5]

Athletes also have an increased risk for dehydration due to the environment and physical exertion. This CDC web page has information about heat illness including dehydration among high school athletes. 

A study done from 2009-2012 with participants ranging from ages 6-19 years old found that inadequate hydration occurred in 54.5% of participants. Of those participants, it was found that males were at increased risk for dehydration.[6]

In children, dehydration is at an increased risk compared to other populations due to increased metabolic rate, high incidence of infection leading to vomiting and diarrhoea (gastroenteritis), and increased body surface area compared to mass.  The elderly and children have the highest risk for dehydration.[7]

Characteristics/Clinical Presentation[1]

Increased thirst, dry mouth, light-headedness, fatigue, impaired mental focus, low urine output, dry skin, inability to produce tears, sunken eyes are the signs of dehydration. [8]

Mild Dehydration
Moderate Dehydration
Severe Dehydration
  • flushed face
  • thirst
  • dry, warm skin
  • cannot pass urine or reduced amounts, dark, yellow coloring
  • light shade of yellow urine
  • weakness
  • cramping in arms and legs
  • unwell
  • headaches
  • dry mouth/lips, dry tongue; with thick saliva
  • lightheadedness, worse when standing
  • irritable or sleepy
  • crying with no or few tears (mainly in children)
  • low BP (postural hypotension[9])
  • headaches[9]
  • darker shade of yellow urine
  • fainting
  • severe muscle contractions in arms, legs, stomach, and back
  • convulsions
  • bloated stomach
  • heart failure
  • sunken fontanelle (soft spot on infant's head)
  • sunken dry eyes
  • skin loses firmness and looks wrinkled
  • lack of elasticity of skin
  • rapid and deep breathing
  • fast, weak pulse
  • decline consciousness
  • increased heart rate (radial pulse may be undetectable)
  • decreased or low blood pressure
  • effects are more pronounced
  • peripheral cyanosis
  • confusion, lethargy, irritability[9]
  • cold hands and feet[9]
  • unable to urinate[9]
  • hypovolaemic shock
  • effects are more pronounced
  • death may occur, if rehydration is not started quickly

Increased tiredness, headaches, nausea, and paresthesias are experienced at about 5% to 6% water loss. With 10% to 15% fluid loss, may experience symptoms of muscle cramping, dry and wrinkly skin, beginning of delirium, painful and/or decreased urine output, and decline in eyesight. Losses of water greater than 15% are usually fatal.

When to seek medical attention:[10]

  • Constant or increased vomiting for greater than a 24 hour period
  • Diarrhoea greater than two days
  • Fever over 101o degrees
  • Decreased urine production
  • Weakness
  • Confusion

Associated Co-morbidities [11]

Physiological Factors Functional Factors Environmental Factors Disease-Related and Iatrogenic Factors 

- Age >85

- female

- Reduced total body water

- Reduced body weight

- Altered renal function

- Reduced sensation of thirst

- Reduced mobility

- Communication difficulties

- Reduced oral intake <l,500ml/day

- Poor manual dexterity

- Self-neglect, Somnolence

- Fear of incontinence

- Fear of nocturia

- Hospitalization

-Insufficient caregivers and understaffing

- Untrained carers

- Hot weather

 - Overheated environment

- Isolation

- Alzheimer's disease
- Increased fluid loss, for example, diarrhoea, vomiting, fever, polyuria, wounds. 

- Reduced fluid intake, for example, anorexia, 

- dysphagia, depression, dementia, confusion,

- Laxatives, diuretics, lithium

- Dietary or fluid restrictions, 

- Polypharmacy: more than four medications. 

- Nil by mouth, for example, fasting for procedures

Diagnostic Tests

A Primary Care Physician can often diagnose dehydration based off of a person's physical signs and symptoms such as skin turgor, color of urine, low blood pressure, rapid heart rate, and sunken eyes.

To help confirm a diagnosis of dehydration and to what degree, a blood test and urinalysis may be performed.[3]

Blood test: can check levels of electrolytes like sodium and potassium, and how well one's kidneys are working.

Urinalysis: can show whether a person is dehydrated and to what degree, using 3 evaluation methods: visual exam, dipstick test, and microscopic exam. The dipstick test looks at acidity or pH, concentration, protein, sugar, ketones, bilirubin, evidence of infection, and blood. The microscopic exam looks at white blood cells, red blood cells, epithelial cells, bacteria or yeasts, casts, or crystals.[12]


Acute Dehydration: Weight loss of >4% of body mass within 7 days[2]

  •  Calculate the body weight (wt) loss
  •  Fluid deficit (L) = pre-illness wt – illness wt
  •  % dehydration = (pre-illnesses wt-illness wt)/pre-illness wt x 100%

Capillary Refill: increased time for capillary bed to refill (>2-3 seconds)[2]


External/stress-related causes[1]:

  • Prolonged physical activity without consuming adequate water, especially in a hot environment
  • Prolonged exposure to dry air
  • Survival situations, especially desert survival conditions
  • Blood loss or hypotension due to physical trauma
  • Diarrhoea
  • Hyperthermia
  • Shock
  • Vomiting

Infectious Diseases[1]:

  • Cholera
  • Gastroenteritis
  • Shigellosis
  • Yellow fever


  • Electrolyte imbalance
  1. Hypernatremia
  2. Hyponatremia
  • Excessive alcohol consumption
  • Fasting
  • Patient refusal of nutrition and hydration


  • Severe hyperglycemia, as seen in Diabetes Mellitus
  • Significant injuries to skin, such as burns or mouth sores, or severe skin disease or infection (more water is lost through the skin)

Systemic Involvement

Dehydration can cause serious systemic involvement, especially severe dehydration. Some problems that may occur include heat injury, cerebral oedema, seizures, hypovolemic shock, kidney failure, coma and death[3].

Heat injury: Heat injury occurs most often in individuals who exercise vigorously and sweat excessively. The severity of heat injury ranges from mild heat cramps and heat exhaustion to more life-threatening heatstroke.

Cerebral edema: This condition, also called swelling of the brain, occurs when one is trying to rehydrate. Cerebral oedema occurs when one's body tries to pull too much water back into its cells causing them to swell and rupture.

Seizures: Seizures occur when one's electrolytes, specifically sodium and potassium, are out of balance and send mixed signals between cells. This can lead to involuntary muscle contractions and loss of consciousness.

Hypovolemic shock: This occurs when a low blood volume causes the person's blood pressure and amount of oxygen in the body to drop. This is one of the more serious conditions that can come from dehydration. If not treated, it can become life-threatening.

Urinary and Kidney Dysfunction:  Prolonged or repeated bouts of dehydration may induce Urinary Tract Infections, kidney stones and eventually kidney failure. Kidney failure is potentially a life-threatening problem that occurs when a person's kidneys are no longer able to remove excess fluids and waste from the body.

Coma and death: If severe dehydration isn't treated quickly, it can be fatal.

Differential Diagnosis [13][14]

  • Acidosis, Metabolic
  • Adrenal Insufficiency
  • Alkalosis, Metabolic
  • Bowel Obstruction in the Newborn
  • Burns, Thermal
  • Congenital Adrenal Hyperplasia
  • Diabetes Insipidus
  • Diabetic Ketoacidosis
  • Diarrhoea
  • Eating Disorder: Anorexia
  • Enteroviral Infections
  • Gastroenteritis
  • Hyperkalemia
  • Hypernatremia
  • Hypochloremic Alkalosis
  • Hypoglycemia
  • Hypokalemia
  • Hyponatremia
  • Intestinal Malrotation
  • Intestinal Volvulus
  • Intussusception
  • Neonatal Sepsis
  • Oliguria
  • Pediatric enteroviral infections
  • Pediatric metabolic acidosis/alkalosis
  • Pyloric Stenosis, Hypertrophic
  • Shock
  • Shock and Hypotension in the Newborn
  • Small-Bowel Obstruction
  • Thermal burns

Medical Management

The treatment of dehydration is best corrected with replenishment of necessary water and electrolytes. For minor dehydration, consumption of a sports drink, like Gatorade or Powerade, will be sufficient in rehydrating the body. Note: Solely drinking a sports drink for rehydration for more moderate to severe cases can cause or worsen diarrhoea due to the high level of sugar.[15]

If fever is the cause of dehydration, Acetaminophen, Ibuprofen can be taken orally or as a suppository[16].

Treatment of children:

  1. Oral rehydration solution (Pedialyte or Hydralyte): used to treat children and infants who have diarrhoea, vomiting, and fever. These solutions are able to replenish fluid and electrolytes with a specific ratio of water and salts. Start with a teaspoon (5mL) every 1-5 minutes and increase as tolerated[3].
  2. Older children may be given Gatorade/Powerade in 1:1 ratio with water.  Make your own oral rehydration solution by missing 1/2 teaspoon salt, 6 level teaspoons of sugar and 1 liter (about 1 quart) of safe drinking water. Be sure to measure accurately because incorrect amounts can make the solution less effective or even harmful. Do not give this homemade ORS to children younger than 12. [10]
  3. Avoid certain foods and drinks: milk, sodas, caffeinated beverages, fruit juices, or gelatins can make symptoms worse.

Treatment of Adults:

  1. Water: best for those with mild to moderate dehydration caused by diarrhoea, vomiting, and fever. Other liquids like full-strength fruit juices and soda can make diarrhoea worse.[3]
  2. Avoid salt tablets: they can cause hypernatremic dehydration in which the body is not only short of water but is also in excess of sodium.

More severe cases should be treated by emergency personal. Medical attention in which fluids are administered through an IV may be necessary. The cause of dehydration also needs to be addressed and treated accordingly. [1]

Physical Therapy Management & Prevention 

There is no direct physical therapy intervention for dehydration in the severe category; however, prevention and fluid replacement orally is something physical therapists can influence through patient education. Patients should also be educated about the signs and symptoms of dehydration in order to know when they may need to seek help.  This is done by proper knowledge of hydration.

General Hydration Recommendations from the CDC:

Water.jpg[17] Environmental Factors

Heat [18]

-Being outside on a hot or humid day can cause your body to need more fluids 

-It is recommended by the American Heart Association to drink water before being outdoors in the heat. This way you do not have to play catch up with Hydration when strain has already been placed on the heart.  

Cold [19]

-Fluid intake also needs to be increased in cooler environments. 

-Cool temperatures may blunt thirst

-Inhalation of cold, dry air increases warmth and moisture in the lungs which causes water vapor to be exhaled

-Physical Activity in the cold can increase respiratory water losses by 15-45 mL per hour

-Insulated clothing can also increase perspiration, increasing water loss

Hydration and Exercise

Before exercise: Drink 12-20oz of fluid 2 hours leading up to exercise

During Exercise:

  • <1-hour drink 16-30 oz of water
  •  1-3 hours drink 16-30 oz 6-8% CHO, sodium drink per hour of exercise   
  • >3 hours similar to guidelines for 1-3 hours but increase sodium intake

-Avoid caffeine or alcohol in beverages due to their diuretic effects

-Avoid hyponatremia which can occur by drinking too much fluid. therefore, diluting sodium

-Monitor dehydration with changes in body weight and urine color. Each pound lost during exercise, drink 15-16oz of fluid [20]



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