Potassium

The normal reference range for Potassium is Potassium is held in a tight 3.5-5.2 mmol/L range because the heart is so sensitive to it. A frequent source of a falsely high result is haemolysis — red cells damaged during a difficult blood draw leak potassium — so a borderline-high value with no symptoms is often just repeated.. Reference ranges may vary between laboratories, so always consult your healthcare provider for interpretation.

Critical for maintaining heart rhythm and muscle contractions; abnormal levels can be life-threatening.

High potassium (hyperkalaemia) is dangerous because it can trigger life-threatening heart arrhythmias. The most common true causes are reduced kidney function and medications that retain potassium — ACE inhibitors, ARBs and the diuretic spironolactone. Others include adrenal insufficiency (Addison's disease), acidosis, and tissue breakdown. Very often, though, a high reading is a lab artefact from a haemolysed sample and is not real.

Low potassium (hypokalaemia) also causes muscle weakness and arrhythmias. Causes include fluid losses from vomiting or diarrhoea, diuretic medications, low magnesium (which must be corrected for potassium to recover), excess aldosterone (Conn's syndrome), and shifts into cells during insulin treatment or alkalosis.

Potassium is part of the routine UEC panel and is checked whenever kidney function, blood pressure medications or fluid balance are assessed. It is monitored closely in people on diuretics, ACE inhibitors or ARBs, in chronic kidney disease, and in any acute illness.