FRACTIONAL EXCRETION OF POTASSIUM; FEK

What this test checks

Compares potassium in blood and urine to determine why blood potassium is too high or too low.

Why do people get this test?

Specialist test for puzzling potassium problems.

When you should consider this test

• Unexplained high or low blood potassium
• Hard-to-control blood pressure
• Specialist requested

How to prepare

Both blood and urine sample needed.