Potassium Test

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KEY POINTS

• This test measures the amount of potassium in your child’s blood. Potassium is one of several chemicals in the blood called electrolytes. The test helps to check for problems with the kidneys, adrenal glands, digestive system, muscles, and nerves.
• A small amount of blood is taken from a vein in your child’s arm with a needle. The blood is collected in tubes and sent to a lab.
• Talk to your child’s healthcare provider about what the test results mean and ask any questions you have.

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What is the potassium test?

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

Your child can get potassium from food and supplements. Most children get all the potassium they need from what they eat and drink. Sources of potassium in the diet include

• Leafy greens such as spinach and collards
• Fruit from vines such as grapes and blackberries
• Root vegetables such as carrots and potatoes
• Citrus fruits such as oranges and grapefruit

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 your child is 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 my child for this test?

• Your child may need to avoid taking certain medicines before the test because they might affect the test result. Make sure your child’s healthcare provider knows about any medicines, herbs, or supplements that your child is taking. Ask your provider before stopping any of your child’s regular medicines.
• Talk to your child’s 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 child’s 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 child’s potassium level may be higher than normal are:

• Your child is taking too many potassium supplements
• Your child has an injury such as a burn
• Your child’s kidneys or adrenal glands are not working well
• Your child has internal bleeding
• Your child is 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 falsely high, even though the level of potassium in your child’s body is actually normal. When this happens, your healthcare provider may want to repeat the test.

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

• Your child has had a lot of vomiting or diarrhea
• Your child is taking a medicine that makes the body lose too much potassium such as a diuretic, or “water pill”
• Your child is not getting enough potassium from diet or supplements prescribed by your provider
• Your child has been sweating a lot during exercise
• Your child has a kidney disease that causes the body to get rid of too much potassium
• Your child has an eating disorder, such as bulimia

What if my child’s test result is not normal?

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

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