High and low potassium
A high potassium (hyperkalaemia) can affect the heart's rhythm and, if severe, is a medical emergency. Common contributors include kidney problems and certain medicines (such as some blood-pressure drugs).
A low potassium (hypokalaemia) can cause muscle weakness, cramps and heart-rhythm problems, and often results from fluid losses (vomiting, diarrhoea) or water tablets (diuretics).
Why it is taken seriously
Because potassium has such a direct effect on the heart, levels that are very high or very low are corrected promptly, and an ECG (heart tracing) may be done. A slightly abnormal result, especially if it might be a sample artefact, is often simply rechecked.
Common questions
Can a potassium result be falsely high?
Yes. If red cells break during or after the blood draw ('haemolysis'), potassium can read falsely high, so an unexpected result is often repeated before acting on it.
Related tools
These calculators are designed for healthcare professionals.