Potassium Test

What is the potassium test?

The potassium test measures the amount of potassium in your blood. Potassium is one of several elements in the blood called electrolytes. Potassium is very important for normal heart and nervous system function. For example, a very high or very low blood level of potassium can lead to serious and even fatal heart rhythm problems.

Why is this test done?

The potassium level is usually measured with several other blood factors to look for certain diseases. The test can be helpful in evaluating disorders of the heart, kidneys, adrenal glands, muscles, and digestive system.

This test may also be done to check certain medical treatments. Some medicines can cause the body's potassium level to go up or down. Some medicines, such as digoxin, don't work well if your 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. Don't stop any of your regular medicines without first consulting with your healthcare provider.
• Talk to your healthcare provider if you have any questions about the test.

How is the test done?

A small amount of blood is taken from your arm with a needle. The blood is collected in tubes and sent to a lab.

Having this test will take just a few minutes of your time.

How will I get the test result?

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

What does the test result mean?

The normal potassium range for adults in most labs is 3.5 to 5.5 milliequivalents per liter (mEq/L). This range may vary slightly from lab to lab. Normal ranges are usually shown next to your test result in the lab report.

Your blood level of potassium may be higher than normal (a condition called hyperkalemia) because:

• 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, are examples of these medicines.

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 ask you to repeat the test.

Your potassium level may be lower than normal (a condition called hypokalemia) because:

• You have had a lot of vomiting or diarrhea.
• You are taking a medicine, such as a diuretic (“water pill”), that makes your body lose too much potassium.
• You are not getting enough potassium from your diet or from potassium supplements prescribed by your provider.
• You have been sweating a lot during exercise.
• You have 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 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.

If your test results are not normal, ask your healthcare provider:

• if you need additional tests
• what you can do to work toward a normal value
• when you need to be tested again.