Sodium urine test

Definition

The sodium urine test measures the amount of sodium in a certain amount of urine.

Sodium can also be measured in a blood sample.

Alternative Names

Urinary 24 hours sodium; Urine Na+

How the Test is Performed

After you provide a urine sample, it is tested in the lab. If needed, the health care provider may ask you to collect your urine at home over 24 hours. Your provider will tell you how to do this. Follow instructions exactly so that the results are accurate.

How to Prepare for the Test

Your provider will ask you to temporarily stop taking any medicines that may affect the test result. Tell your provider about all the medicines you take, including:

• Corticosteroids
• Nonsteroidal anti-inflammatory drugs (NSAIDs)
• Prostaglandins (used to treat conditions such as glaucoma or stomach ulcers)
• Water pills (diuretics)

DO NOT stop taking any medicine before talking to your provider.

How the Test will Feel

The test involves only normal urination. There is no discomfort.

Why the Test is Performed

The test is often used to help determine the cause of an abnormal sodium blood level. It also checks whether your kidneys are removing sodium from the body. It may be used to diagnose or monitor many types of kidney diseases.

Normal Results

For adults, normal urine sodium values are generally 20 mEq/L in a random urine sample and 40 to 220 mEq per day. Your result depends on how much fluid and sodium or salt you take in.

The examples above are common measurements for results of these tests. Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your provider about the meaning of your specific test result.

What Abnormal Results Mean

A higher than normal urine sodium level may be due to:

• Certain medicines, such as water pills (diuretics)
• Low function of the adrenal glands
• Inflammation of the kidney that results in salt loss (salt-losing nephropathy)
• Too much salt in the diet

A lower than normal urine sodium level may be a sign of:

• Adrenal glands releasing too much hormone (hyperaldosteronism)
• Not enough fluid in the body (dehydration)
• Diarrhea and fluid loss
• Heart failure
• Kidney problems, such as long-term (chronic) kidney disease or kidney failure
• Scarring of the liver (cirrhosis)

Risks

There are no risks with this test.

References

Kamel KS, Halperin ML. Interpretation of electrolyte and acid-base parameters in blood and urine. In: Yu ASL, Chertow GM, Luyckx VA, Marsden PA, Skorecki K, Taal MW, eds. Brenner and Rector's The Kidney. 11th ed. Philadelphia, PA: Elsevier; 2020:chap 24.

Oh MS, Briefel G. Evaluation of renal function, water, electrolytes, and acid-base balance. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 23rd ed. St Louis, MO: Elsevier; 2017:chap 14.

Villeneuve P-M, Bagshaw SM. Assessment of urine biochemistry. In: Ronco C, Bellomo R, Kellum JA, Ricci Z, eds. Critical Care Nephrology. 3rd ed. Philadelphia, PA: Elsevier; 2019:chap 55.