Risks

There is no chance for problems in collecting a one-time or 24-hour urine sample.

Results

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.

Normal

Normal results may vary from lab to lab. Results are ready in 1 day.

Many conditions can affect sodium levels. Your doctor will talk with you about any abnormal results that may be related to your symptoms and medical history.

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

• Taking medicines, such as birth control pills, corticosteroids, antibiotics, estrogens, tricyclic antidepressants, heparin, nonsteroidal anti-inflammatory drugs (NSAIDs), diuretics, lithium, and many medicines used to treat high blood pressure.
• Having high levels of glucose, triglycerides, or protein.
• Getting sodium in intravenous (IV) fluids given during a recent surgery or hospitalization.

What To Think About

• Sodium levels can also be measured in a blood test. For more information, see the medical test Sodium (Na) in Blood.
• 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.
• To see whether the body is passing too little or too much sodium in the urine, a value called the fractional excretion of sodium (FENa) can be found by looking at the amounts of sodium and creatinine in blood and urine. In a person with kidney failure, a low FENa may mean less blood flow to the kidneys is causing the kidney failure.

Other Works Consulted

• Chernecky CC, Berger BJ (2008). Laboratory Tests and Diagnostic Procedures, 5th ed. St. Louis: Saunders.

• Pagana KD, Pagana TJ (2006). Mosby’s Manual of Diagnostic and Laboratory Tests, 3rd ed. St. Louis: Mosby.