What is a sodium test?

This test measures the amount of sodium in your blood. Sodium 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 sodium and other electrolytes in your body to stay healthy. 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.

Salt is often the main source of sodium in your diet.

Why is this test done?

The sodium 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.

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.
• Your healthcare provider will tell you when to stop eating and drinking before the test. Food and drink before the test may affect the results.
• 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 sodium level may be higher than normal are:

• You have a lot of salt in your diet.
• 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.

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

• You have had a lot of vomiting or diarrhea.
• You have had a burn.
• Your kidneys or adrenal glands are not working well.
• You have been drinking a lot 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, 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