Dehydration is understood as excessive loss of body fluids and ions. In internal medicine it is a very common problem, because it affects many elderly patients. Dehydration is a major causative factor of admission to hospital. Dehydration sometimes "just" accompanies other diseases whose course it usually worsens.


Note: Similarly, dehydration is a problem in pediatric wards mainly due to the ease of dehydration development in children. This will, however, not be further discussed in this article due to author’s lack of experience with pediatric issue, we will rather focus on causes, symptoms and treatment of dehydration in an adult patient.


Dehydration is typical for the elderly. It contributes to fragility of old, to often difficult compliance and various forms of dementia. In advanced age, feeling of thirst often disappears. Thirst is a defense mechanism and its reduction leads to easy development of dehydration. The elderly often doesn’t fell thirst even by serious fluid deficiency and that is why they should be regularly actively encouraged to fluid intake. There are, however, a number of pathological conditions in which dehydration can occur in even much younger patients:

Elevated body temperature

Elevated body temperature is typically associated with higher loss of body fluids. One degree Celsius above normal means approximately 500 milliliters of extra fluid demand. In addition, fatigue and lethargy experienced by individuals with high fever threatens to undermine the willingness to drink. Adequate oral intake of fluids or other compensation of fluid loss is therefore very important in febrile condition.


Diarrhea can cause severe dehydration (especially infectious diarrheas in childhood). This is supported by frequent misconceptions (seemingly logical) that if affected person does not drink, diarrhea will mitigate or even stop. However, this does not happen and by contrast signs of dehydration emerge.


Note: Very severe watery diarrhea accompanied dreaded cholera epidemics in the past. The modern way of effective fluid loss compensation by intravenous infusions decreased significantly mortality in this infectious bacterial disease without any need of antibiotic therapy.


Untreated diabetes is accompanied by various degree of dehydration as a result of blood sugar (glucose) level elevation. If it exceeds a certain value, the glucose is excreted into urine and takes water and ions with. People with hyperglycemia (high blood sugar) have therefore rather dry skin, while a person with hypoglycemia (low blood sugar) has rather damp and sweaty skin.


Dehydration cases caused by these drugs are very frequent from the perspective of internal medicine physicians. Diuretics are prescribed in many diseases, especially in heart failure, and in the treatment of hypertension (antihypertensives). These drugs increase the loss of ions and a body fluid in kidneys and their high doses may easily dehydrate anyone.

Diabetes insipidus

This is a hormonal disorder. There are two forms of this disease. In first form human body doesn’t produce enough antidiuretic hormone, whereas in second form kidney tissue is resistant to antidiuretic hormone effect. In normal conditions antidiuretic hormone prevents fluid and mineral losses into urine by influencing kidney tissue. The disease has different degrees of severity. It is accompanied by terrible thirst and in severe forms it can cause a loss of over 15 liters of fluid a day.

Bartter syndrome

This is a rare genetic disease with impaired renal tubules absorption resulting in loss of ions and fluid into the urine.


Mild dehydration may have virtually no symptoms. Normally, thirst appears, but by many people it is missing, especially by the elderly. Gradually symptoms appear such as dry mucous membranes and dry skin. Skin folds may occur that are only slowly straightened (reduced skin tension), the tongue is dried off and coated. By people that had already thin skin, dehydration can create so-called parchment skin. Urine is concentrated (the body tries to eliminate as little water as it can) and darkens. Lack of fluid in bloodstream manifests during severe dehydration by a drop in blood pressure and by pulse acceleration. In old people impairment of brain functions occur as confusion, dizziness and increased risk of falling. In the most severe cases dehydration can lead to organs malfunction, unconsciousness and death.


Laboratory tests we may show different abnormalities suggestive of dehydration (decreased renal functions, elevated levels of various compounds in concentrated blood), but the best way in my opinion, is a simple clinical evaluation by physical exam. It is fast and gives us a lot of information. Dehydration diagnostics is made by finding dry skin, lips and tongue and decreased skin tension (try creating a skin fold in area above the collarbone). Evaluation of amount a color of urine is also important. Only small amount of excreted dark urine indicates possible dehydration.


Dehydration must be properly treated, whether it is the main problem or only condition accompanying other disease. For example, dehydration of a patient with ischemic stroke increases irreparably damaged area of the brain. Dehydration is treated by fluid intake. In milder forms it is sufficient to increase per oral fluid intake. Severe forms of dehydration should be treated by administration of intravenous infusions. Intravenous hydration is simple, highly efficient and does not require active cooperation of the patient. There is a variety of infusion preparations that differ by presence or concentration of certain minerals and glucose. When administering intravenous infusions a great caution must be taken in patients with chronic heart disorders connected with its impaired pumping ability. Too sudden and great intravenous fluid delivery may cause volume heart overload and acute heart failure.


Infusion therapy is essential part of terminal dying patient therapy, which include providing adequate intake of fluids and ions and proper analgesic therapy.

Jiri Stefanek, MD  Author of texts: Jiri Stefanek, MD
 Sources: basic text sources