NHS website

Potassium test

Find out why and when a potassium test may be needed.

2 November 2018


A potassium test measures the amount of potassium in blood serum, the fluid part of your blood.

Potassium ↗ is a mineral that helps:

  • nerves and muscles "communicate"
  • nutrients move into cells and waste products move out of cells
  • the heart function healthily

A potassium test may be recommended to help diagnose or monitor kidney disease ↗, which is the most common cause of high potassium levels.

Your doctor may also recommend the test if you have heart-related problems, such as high blood pressure (hypertension) ↗.

If you have low potassium levels, you may have a heart problem, such as an irregular heartbeat ↗.

If you have high potassium levels, your heart muscle activity may be reduced.

Both situations are serious and can be life threatening.

You may also have a potassium test if you have diabetes ↗ and your doctor thinks you may have diabetic ketoacidosis ↗, a complication caused by a lack of insulin in the body.

In rare cases, potassium levels may be low through a poor diet.

Good sources of dietary potassium include:

  • fruit, particularly bananas
  • vegetables
  • pulses
  • nuts and seeds
  • milk
  • fish
  • shellfish
  • beef
  • chicken
  • turkey
  • bread

Read more about the potassium test ↗ on Lab Tests Online UK.