Urine sodium test, Na 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 medications.
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 helps your doctor find out whether you have high blood pressure, kidney damage, or another condition that can threaten your health.
You may need this test if your doctor suspects that you have high blood pressure. You may also have this test to check for kidney damage or to monitor treatment for high blood pressure.
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.
Your doctor 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
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 health care provider.
Results are given in milliequivalents per liter (mEq/L). Normal results for a spot, or one-time, urine sample are 20 mEq/L.
If your results are higher, it may mean that you have kidney damage or a condition that affects your thyroid gland.
This test requires a urine sample. Your doctor will tell you how to collect the sample.
This test poses no known risks.
Eating a diet high in salt or taking medication 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.
You may have to drink a certain amount of water before giving a urine sample. In addition, be sure your doctor 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.