Does this test have other names?
Urine sodium test, Na test
What is this test?
This test measures the amount of sodium, or salt, in your urine.
Sodium is in almost everything you eat. It's found in many processed foods, like pretzels and chips. It's even in some medicines.
Your body needs some sodium to balance other minerals that circulate in your blood and to carry nutrients to different parts of your body. If you get too much sodium, your kidneys normally absorb it and clear it from your body.
But if you have kidney damage, your kidneys may not be able to remove the sodium the way they should. Eating foods with too much sodium can lead to high blood pressure because the sodium causes your body to retain, or hold, water. For instance, too much sodium can cause a fluid buildup in your legs.
Checking the sodium level in your urine is usually done if your blood sodium level is not normal. This test helps your healthcare provider find out whether you have kidney damage or another condition that can threaten your health.
Why do I need this test?
You may need this test if you had abnormal results on a sodium blood test. This test will help your healthcare provider understand the cause of your sodium imbalance. If you have high blood pressure, your provider may use this test to find out if it's because you have too much salt in your diet. You may also have this test to check for kidney damage or to monitor treatment for conditions that affect your sodium levels.
You may also need this test if you have lost a lot of water because of vomiting or diarrhea. After vomiting or diarrhea, your sodium levels may be normal but more concentrated because you have lost so much liquid.
What other tests might I have along with this test?
Your healthcare provider may also order other tests to see how well your kidneys are working and blood tests to measure other substances in your body. These tests include:
Glomerular filtration rate, or GFR, to measure the amount of fluid your kidneys filter
Blood urea nitrogen, or BUN
What do my test results mean?
Many things may affect your lab test results. These include the method each lab uses to do the test. Even if your test results are different from the normal value, you may not have a problem. To learn what the results mean for you, talk with your healthcare provider.
Results are given in milliequivalents per liter (mEq/L). Normal results for a spot, or one-time, urine sample are 20 mEq/L.
Abnormal results may be caused by:
Kidney, heart, or liver problems
A condition that affects your thyroid gland
Medicines such as water pills (diuretics)
Too much salt in your diet
A condition that affects your sodium levels
How is this test done?
This test requires a urine sample. Your healthcare provider will tell you how to collect the sample.
Does this test pose any risks?
This test poses no known risks.
What might affect my test results?
Eating a diet high in salt or taking medicine for high blood pressure can affect your results. Your results may also be affected if you have been vomiting or if you've lost fluids because of diarrhea.
How do I get ready for this test?
You may have to drink a certain amount of water before giving a urine sample. In addition, be sure your healthcare provider knows about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illicit drugs you may use.
March 22, 2017
Evaluating the Labs. Practical Guide to the Care of the Medical Patient. Ferri FF. 2010, 8th ed., Evaluation of adults with hyponatremia. UpToDate., Urine Assessment. Brenner and Rector's The Kidney. Taal MW. 2011, 9th ed.
Turley, Ray, BSN, MSN,Walton-Ziegler, Olivia, MS, PA-C