Serum Potassium (K)

Potassium level, heart & muscles

Potassium is a mineral that the heart, muscles and nerves need to work properly. The kidneys keep blood potassium within a narrow range, and levels that are too high or too low can affect the heartbeat. This test measures the potassium in your blood and is often checked in kidney disease and in people taking medicines that affect potassium.

• In people taking blood pressure medicines, water tablets or potassium supplements
• To check people with kidney disease, in whom potassium can build up
• After vomiting or diarrhoea, which can cause potassium loss
• To look into muscle weakness, cramps or an irregular heartbeat
• As part of routine electrolyte checks in diabetes or during illness

Potassium can be checked without fasting. Keep taking your usual medicines unless your doctor says otherwise, and tell your doctor about any potassium supplements or salt substitutes you use. During the draw, keep your hand relaxed rather than repeatedly clenching your fist, as this can falsely raise potassium.

Sample

Blood sample

How it works

At the home visit, the collector draws a small blood sample from a vein in your arm. Potassium can leak out of blood cells if the sample is handled roughly or left standing, which is one reason an unexpected result is sometimes repeated.

Report

Within 24 hours of collection.

A high potassium (hyperkalaemia) can be caused by kidney disease, some blood pressure medicines, certain water tablets, potassium supplements or uncontrolled diabetes, and can also be falsely high if blood cells break in the sample. A low potassium (hypokalaemia) is often caused by vomiting, diarrhoea or water tablets. Both high and low levels can cause muscle weakness and dangerous changes in heart rhythm. Your doctor will interpret the result and may repeat it or act on it urgently.

One test: Serum Potassium (K), from one blood sample.