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Home > Health Library > Sodium (Na) in Urine
A test for sodium in the urine is a 24-hour test or a one-time (spot) test that checks how much sodium is in the urine. Sodium is both an electrolyte and a mineral. It helps keep the water (the amount of fluid inside and outside the body's cells) and electrolyte balance of the body. Sodium is also important in how nerves and muscles work.
Most of the sodium in the body (about 85%) is found in blood and lymph fluid. Sodium levels in the body are partly controlled by a hormone called aldosterone, which is made by the adrenal glands. Aldosterone levels tell the kidneys when to hold sodium in the body instead of passing it in the urine. Small amounts of sodium are also lost through the skin when you sweat.
Doctors may look at urine sodium and blood sodium levels to see whether conditions or medicines may be causing fluid or electrolyte imbalances. Urine sodium levels are often high when blood levels are low or low when blood levels are high. Urine sodium levels are affected by medicines and hormones. Low urine sodium levels have many causes, such as heart failure, malnutrition, or diarrhea.
A urine test to check sodium levels is done to:
You do not need to do anything before having this test.
Talk to your doctor about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will mean. To help you understand the importance of this test, fill out the medical test information form( What is a PDF document? ).
Urine sodium can be checked in a single urine sample but it is more often measured in a 24-hour urine sample.
There is no discomfort in collecting a one-time or 24-hour urine sample.
There is no chance for problems in collecting a one-time or 24-hour urine sample.
A test for sodium in the urine is a 24-hour test or a one-time (spot) test that checks how much sodium is in the urine. Sodium is both an electrolyte and a mineral.
The normal values listed here—called a reference range—are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what's normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.
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40–220 milliequivalents (mEq)/day or 40–220 millimoles (mmol)/day (SI units)
41–115 mEq/day or 41–115 mmol/day
Greater than 20 milliequivalents per liter (mEq/L)
Many conditions can affect sodium levels. Your doctor will talk with you about any abnormal results that may be related to your symptoms and past health.
Reasons you may not be able to have the test or why the results may not be helpful include:
Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.
Pagana KD, Pagana TJ (2010). Mosby's Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.
Current as of:
March 28, 2019
Author: Healthwise StaffMedical Review: Adam Husney MD - Family MedicineE. Gregory Thompson MD - Internal MedicineMartin J. Gabica MD - Family Medicine
Current as of:
March 28, 2019
Medical Review:Adam Husney MD - Family Medicine & E. Gregory Thompson MD - Internal Medicine & Martin J. Gabica MD - Family Medicine
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