Tests for Potassium Levels

Potassium (chemical symbol K) conducts nerve impulses and keeps the heart beating and muscles working. Tests can be performed directly on blood or indirectly by measuring heart activity with an electrocardiogram.

How Long Do Tests Take?

• A basic metabolic panel takes under an hour. A blood gas analyzer checks levels in minutes. High potassium levels may kill a person in seconds; levels can only be estimated with an electrocardiogram and a cardiac monitor.

What Steps Are There?

• To obtain blood, a tourniquet is placed on the arm, the skin is cleaned with an antiseptic, and a needle is inserted into the vein. Blood flows into a tube, is sent to the lab, spun rapidly in a centrifuge, and the unclotted liquid (serum), is analyzed in a machine.

Can the Tests Be Wrong?

• Potassium can leak out of cells that break open, causing false high levels.

What Does a High Level Mean?

• If levels get too high, called hyperkalemia, a person's heart can stop. Potassium levels rise when the kidneys fail.

What Does a Low Level Mean?

• If levels are too low, called hypokalemia, a person can become weak, and the heart goes into a life-threatening rhythm. Potassium can be lost in vomit or diarrhea.