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All information on dehydration

At a glance

Dehydration is a poor fluid balance of the organism. This condition can be caused on the one hand by a high loss of fluid, for example by heavy sweating or severe diarrhea, or by insufficient fluid intake. Persistent dehydration leads to exsiccosis, a regular dehydration of the body.

Further information

The following characteristics are distinguished

Isotonic dehydration

The loss of water and electrolytes such as sodium are balanced. In isotonic dehydration, serum osmolality is normal. This means that the concentration of particles is not increased in relative terms due to the lack of water, as the electrolyte concentration is also lowered. Since there are other substances in the urine, the specific urine weight is increased.


Hypotone dehydration

In hypotonic dehydration, the loss of electrolytes and salt (sodium) is greater than the loss of water. Due to the hypotension of the extracellular fluid, intracellular edema formation occurs due to osmosis. Clinically, in addition to symptoms of hypovolemia, which can also be observed with isotonic dehydration, there are also cerebral symptoms that are due to an incipient cerebral edema. These include drowsiness, confusion, and seizures.


Hypertone dehydration

Hypertonic dehydration is characterized by a stronger water than electrolyte deficiency. Due to the hypertension of the extracellular fluid, there is an osmotic outflow of water from the cell into the extracellular space.



  • 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 nursinghomes 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.


  • Hartig, W. (2004): Ernährungs- und Infusionstherapie, Georg Thieme Verlag
  • Gerlach, U. et al. (2015): Innere Medizin für Gesundheits- und Krankenpflege , Georg Thieme Verlag
  • Antwerpes F. et al.: Dehydration, URL:
  • Feichter, M. & Schrör S. (2019): Dehydration, URL:
  • Wüst, W. (2011): Common and dangerous in old patients, URL:
  • Huppelsberg, J. & Walter, K. (2013): Kurzlehrbuch Physiologie, Georg Thieme Verlag
  • Striebel, H.W. (2014): Operative Intensivmedizin, Schattauer Verlag
Status of information: 2022