All information on dehydration

At a glance

Dehydration is a decrease in the body fluid or body water of an organism. Massive dehydration leads to exsiccosis.

For more information

The following characteristics are distinguished

Isotonic dehydration

The loss of water and sodium keep the balance. In isotonic dehydration, serumosmolality is normal, which increases specific urine weight.


Hypotone dehydration

In hypotonic dehydration, the salt loss (sodium loss) is greater than the water loss. The hypotension of the extracellular fluid leads to intracellular edema formation (osmosis). Clinically, in addition to symptoms of hypovolemia, as in isotonic dehydration, there are also cerebral symptoms due to incipience of cerebral edema. The cerebral symptoms include drowsiness, confusion and seizures.


Hypertone dehydration

Hypertone dehydration is characterized by a lack of free water. Important causes of hypertonic dehydration are the diabetic coma or even diabetes insipidus. The hypertension of the extracellular fluid leads to a relatively higher intracellular water deficiency.



  • Lack of concentration
  • Strongly coloured to dark urine, decrease in amount of urine
  • Brittle to cracked lips
  • Thirst, dry mouth and dry tongue
  • Headache
  • Fatigue, weakness
  • Dizziness
  • Dry, itchy skin
  • Weight loss


In the case of an exsiccosis :


Risk factors/causes

  • Too low drinking, especially during physical exertion under hot temperatures
  • Diarrhoea (e.g. gastroenteritis)
  • vomiting
  • Diabetic coma
  • Blood poisoning (sepsis)
  • Combustion
  • Addison’s disease
  • Acute renal failure (polyuric phase)
  • Diabetes insipidus


Urine diagnostics



  • The therapy consists in a substitution of water by intravenous infusion, adapted to the respective form of dehydration. Depending on the clinical symptoms, the substitution of 2-4 l, sometimes much more water is necessary. Subcutaneous infusions are also used in nursing homes and geriatric care.
  • In isotonic dehydration, an isotonic solution for infusion such as the ringer solution can be used relatively easily for rehydration.
  • In hypotonic dehydration, sodium should be substituted at sodium levels below 125 mmol/l in addition to the isotonic solution
  • In hypertonic dehydration, the substitution of free water takes place, for example by 5-degree glucose solution.


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  • Gerlach, U. et al. (2015): Innere Medizin für Gesundheits- und Krankenpflege , Georg Thieme Verlag
  • Antwerp F. et al.: Dehydration, URL:, Retrieved 18.06.2019
  • Feichter, M. & Schrör S. (2019): Dehydration, URL:, Retrieved 18.06.2019
  • Wüst, W. (2011): Bei alten Patienten häufig und gefährlich, URL:, Retrieved 18.06.2019
  • Huppelsberg, J. & Walter, K. (2013): Kurzlehrbuch Physiologie, Georg Thieme Verlag
  • Striebel, H.W. (2014): Operative Intensivmedizin, Schattauer Verlag
Status of information: Autumn 2019