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Sodium - urine

Definition

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

How the test is performed

Urine may be collected over a 24-hour period or by the "clean-catch" method. The urine is then analyzed by a laboratory.

If a 24-hour urine sample is needed, your health care provider will instruct you, if necessary, to discontinue drugs that may interfere with the test.

On day 1, urinate into the toilet when you get up in the morning.
Afterwards, collect all urine in a special container for the next 24 hours.
On day 2, urinate into the container when you get up in the morning.
Cap the container. Keep it in the refrigerator or a cool place during the collection period. Label the container with your name, the date, the time of completion, and return it as instructed.

Collect a "clean-catch" (midstream) urine sample. To obtain a clean-catch sample, men or boys should clean the head of the penis. Women or girls need to wash the area between the lips of the vagina with soapy water and rinse well. As you start to urinate, allow a small amount to fall into the toilet bowl to clear the urethra of contaminants. Then, put a clean container under your urine stream and catch 1 to 2 ounces of urine. Remove the container from the urine stream. Cap and mark the container and give it to the health care provider or assistant

Infant:

Thoroughly wash the area around the urethra. Open a urine collection bag (a plastic bag with an adhesive paper on one end), and place it on the infant. For boys, the entire penis can be placed in the bag and the adhesive attached to the skin. For girls, the bag is placed over the labia. Diaper as usual over the secured bag.

This procedure may take a couple of attempts. The infant should be checked frequently and the bag changed after the infant has urinated into the bag. The urine is drained into the container for transport to the laboratory.

Deliver it to the laboratory or your health care provider as soon as possible upon completion.

How to prepare for the test

No special preparation is necessary for this test, but if the collection is being taken from an infant, a couple of extra collection bags may be necessary.

The health care provider may advise you to discontinue drugs that can affect the test (see Special Considerations).

How the test will feel

The test involves only normal urination, and there is no discomfort.

Why the test is performed

The test is often used to determine hydration status and the kidney's ability to conserve or excrete sodium.

Aldosterone (see the aldosterone test), a hormone produced by the adrenal gland, plays a major role in regulating sodium levels within the body and urine. Specifically, aldosterone increases the reabsorption of sodium in the kidneys at the expense of potassium and hydrogen loss.

Reabsorption of sodium helps retain water in body tissues and the blood stream. This way, aldosterone helps maintain plasma volume and blood pressure. Dehydration and conditions that decrease kidney blood flow stimulate aldosterone production.

Normal Values

Normal values are generally 15 to 250 mEq/L/day, depending on hydration status and daily intake of dietary sodium. Normal value ranges may vary slightly among different laboratories.

Note: mEq/L/day = milliequivalents per liter per day

What abnormal results mean

Higher-than-normal urine sodium levels may indicate excessive salt intake.

Lower-than-normal urine sodium levels may indicate: