What is the potassium test?

This test measures the amount of potassium in your blood. Potassium is one of several chemicals in the blood called electrolytes. Electrolytes help control the amount of fluid in your body and the way your muscles, nerves, and organs work, including your heart. You need the right balance of potassium and other electrolytes in your body to stay healthy. For example, too much or too little potassium in the blood could cause serious problems with your heartbeat. The balance of electrolytes in your body can be affected by food, medicines, drinking too much or too little water, or problems with your lungs, kidneys and other organs.

You can get potassium from food and supplements.

Why is this test done?

The potassium level is usually measured along with several other electrolytes to help diagnose certain diseases or conditions. The test can be helpful for checking problems with the kidneys, adrenal glands, digestive system, muscles, and nerves.

This test may also be done to see how well treatment for a disease or condition is working or, if you are hospitalized, to see if your child is getting the right mix of IV fluids. Some medicines can cause the potassium level to go up or down. Other medicines, such as digoxin, don’t work well if the potassium level isn’t normal.

How do I prepare for this test?

• You may need to avoid taking certain medicines before the test because they might affect the test result. Make sure your healthcare provider knows about any medicines, herbs, or supplements that you are taking. Ask your provider before stopping any of your regular medicines.
• Talk to your healthcare provider if you have any questions about the test.

How is the test done?

Having this test will take just a few minutes. A small amount of blood is taken from a vein in your arm with a needle. The blood is collected in tubes and sent to a lab.

Ask your healthcare provider when and how you will get the result of the test.

What does the test result mean?

Some of the reasons your potassium level may be higher than normal are:

• You are taking too many potassium supplements.
• You have an injury, like a burn.
• Your kidneys or adrenal glands are not working well.
• You have internal bleeding.
• You are taking certain types of blood pressure medicines that cause the body to hold onto extra potassium, such as:
  • ACE inhibitors, such as captopril and enalapril
  • Potassium-sparing diuretics, such as spironolactone
• Sometimes red blood cells break as they pass through the needle into the blood-collecting tube. The cells may release potassium when this happens and cause the test result to be high, even though the level of potassium in your body is actually normal. When this happens, your healthcare provider may want to repeat the test.

Some of the reasons your potassium level may be lower than normal are:

• You have had a lot of vomiting or diarrhea.
• You are taking a medicine that makes your body lose too much potassium (for example, a diuretic, or “water pill”).
• You are not getting enough potassium from your diet or supplements prescribed by your provider.
• You have been sweating a lot during exercise.
• You have a kidney disease that causes you to get rid of too much potassium.
• You have an eating disorder, such as bulimia.

What if my test result is not normal?

Test results are only one part of a larger picture that takes into account your medical history, physical exam, and current health. Sometimes a test needs to be repeated to check the first result. Talk to your healthcare provider about the results and ask questions, such as:

• If you need more tests
• What kind of treatment you might need
• What lifestyle, diet, or other changes you might need to make