Blood (Serum) Sodium Test

What is the blood (serum) sodium test?

This 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 serum sodium level 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, 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 health care provider knows about any medicines, herbs, or supplements that you are taking.
• Talk to your health care 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 of your time. There is no risk of getting AIDS, hepatitis, or any other blood-borne disease from this test.

How will I get the test result?

Ask your heath 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.
• 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.

Drugs that can affect your test result are:

• blood pressure medicines
• corticosteroids
• diuretics.

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 health care provider about your result and ask questions.

If your test results are not normal, ask your health care provider:

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