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Sodium Test

What is a sodium test?

A sodium test measures the amount of sodium in your blood. Sodium is one of several elements in blood called electrolytes. You may already be familiar with sodium as sodium chloride, or table salt. The test is sometimes called a serum sodium test.

Why is this test done?

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

This test may also be done to check certain medical treatments. Some medicines can cause the body's sodium level to go up or down.

How do I prepare for this test?

  • You don't need to fast or limit your activity before the 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.

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.

How will I get the test result?

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

What does the test result mean?

The normal blood sodium range for adults in most labs is 135 to 145 milliequivalents (mEq) per liter. The normal range may vary slightly from lab to lab. Normal ranges are usually shown next to your results in the lab report.

Your blood level of sodium may be higher than normal because:

  • You eat a lot of salt.
  • You have not been drinking enough fluids and are dehydrated.
  • Your thyroid level is low.
  • You have recently eaten licorice.
  • You have been hyperventilating.
  • You have kidney disease.

Your blood level of sodium may be lower than normal because:

  • You have had a lot of vomiting or diarrhea.
  • You have had a burn.
  • Your kidneys or adrenal glands aren't working well.
  • You have been drinking excessive amounts of water.
  • You have liver or heart disease.
  • You have been exercising a lot (for example, just run a marathon).

Some medicines can affect the test results, such as diuretics (water pills).

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 your result 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.
Written by Tom Richards, MD, for RelayHealth.
Published by RelayHealth.
Last modified: 2011-06-26
Last reviewed: 2011-05-03
This content is reviewed periodically and is subject to change as new health information becomes available. The information is intended to inform and educate and is not a replacement for medical evaluation, advice, diagnosis or treatment by a healthcare professional.
© 2011 RelayHealth and/or its affiliates. All rights reserved.
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