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Total Body Potassium and ECF Estimates

Total Body Potassium


Total Body Potassium

Key facts:

  • Potassium is the major intracellular cation. 98% of the total body potassium is in the intracellular compartment with only 2% located extracellularly (plasma).
  • The ratio of intracellular to extracellular potassium is the major determinant of the resting membrane potential. It  helps establish the resting membrane potential in neurons and muscle fibers.
  • Potassium has very little effect on osmotic pressure unlike sodium in the ECF.
  • Potassium is excreted, both actively and passively, through the renal tubules, especially the distal convoluted tubule and collecting ducts.
  • The primary substance regulating the serum potassium concentration is aldosterone.
  • The daily intake of potassium in the western diet is between 80-120 mmol.
  • The kidney is the major route of potassium excretion, accounting for 90% of potassium loss daily. The remaining 10% is excreted through the gastrointestinal tract.
  • The kidney is responsible for long term potassium homoeostasis.

Potassium Content in the Body

  • Dependent on sex, age, and, most importantly, muscle mass which contains 60 to 75% of total body potassium.
  • Total body potassium estimates for normal adult women and men:
    Female: approximately 40 to 45 mmol/Kg
    Male:  50 to 55 mmol/kg of body weight.
    Elderly:  Values are 20% less (decrease in muscle mass).
    Intracellular (ICF):  ~2% of total body potassium.


Required Entries

Data points:


Patient Height: 


Is the patient elderly (65 years of age or older) ?




Reference top of page

Cheng YL, Yu AW. ELECTROLYTES - Water-Electrolyte Balance: in Encyclopedia of Food Sciences and Nutrition (Second Edition), Oxford: 2003.

Potassium Content in the Body:
The total body potassium content is dependent on sex, age, and, most importantly, muscle mass (which contains 60-75% of total body potassium), and is approximately 40-45, and 50-55 mmol per kilogram of body weight for normal adult women and men, respectively. These values decrease with age and are 20% less in the elderly because of a decrease in muscle mass.


References top of page


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Total Body Potassium and ECF Estimates