Potassium - urine

Alternative names
Urine potassium

Definition
The potassium urine test measures the amount of potassium in the urine.

How the test is performed
A spot urine potassium or a 24-hour urine potassium sample may be performed.
Your health care provider will instruct you, if necessary, to discontinue drugs that may interfere with the test. A 24-hour Urine collection is usually performed as follows:

     
  • 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.

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 males, the entire penis can be placed in the bag and the adhesive attached to the skin. For females, the bag is placed over the labia. Diaper as usual over the secured bag.

This procedure may take a couple of attempts - lively infants can displace the bag, causing the specimen to be absorbed by the diaper. 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.

How the test will feel
This test involves only normal urination, and there is no discomfort.

Why the test is performed
This test is usually performed to detect or confirm the presence of conditions that affect body fluids (for example, dehydration, vomiting, diarrhea) or disorders of the kidneys or adrenal glands, which are the source of aldosterone. For more information see the aldosterone test.

The serum (blood) and urine potassium depend on many factors. Aldosterone is a steroid hormone that plays a major role in regulating potassium levels within the body. Aldosterone increases the loss of potassium in the kidneys. Potassium is also affected by acid/base balance because potassium exchanges with hydrogen, to some extent, across cell membranes.

Normal Values
The usual range for a person on a regular diet is 25 to 120 mEq/L/day. However, lower or higher urinary levels may occur depending on dietary potassium intake and the relative amount of potassium in the body. Normal value ranges may vary slightly among different laboratories.

Note: mEq/L = milliequivalents per liter

What abnormal results mean

Greater-than-normal urine potassium levels may indicate:

     
  • Acute tubular necrosis  
  • Cushing’s syndrome (rare)  
  • Diabetic acidosis and other forms of metabolic acidosis  
  • Hyperaldosteronism (very rare)  
  • Eating disorders (anorexia, bulimia) and vomiting  
  • Low magnesium levels

Additional conditions under which the test may be performed include medullary cystic disease.

What the risks are
There are no risks.

Special considerations
Deficient or excessive amounts of potassium in the diet may affect test results.

Drugs that can increase urine potassium measurements include diuretics, glucocorticoids, certain antibiotics, and NSAIDS.

Johns Hopkins patient information

Last revised: December 3, 2012
by Gevorg A. Poghosian, Ph.D.

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