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Potassium - urine

Definition

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

Alternative Names

Urine potassium

How the test is performed

This test may be done with a random urine sample or a 24-hour urine sample.

If a 24-hour urine sample is needed:

• 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.

For an 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, place the entire penis in the bag and attach the adhesive to the skin. For females, place the bag over the labia. Diaper as usual over the secured bag.

This procedure may take a couple of attempts -- lively infants can move the bag, causing the urine to be absorbed by the diaper. Check the infant frequently and change the bag after the infant has urinated into it. Drain the urine from the bag into the container provided by your health care provider.

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

How to prepare for the test

If the collection is being taken from an infant, a couple of extra collection bags may be necessary.

Your health care provider may tell you to temporarily stop taking certain drugs that may affect test results. Drugs that can affect urine potassium measurements include:

• Certain antibiotics
• Diuretics
• Glucocorticoids
• Nonsteroidal anti-inflammatories

How the test will feel

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

Why the test is performed

Your doctor may order this test if you have signs of a condition that affects body fluids. This may include dehydration, vomiting, or diarrhea.

It may also be done to diagnose or confirm disorders of the kidneys or adrenal glands.

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

Normal Values

The usual range for a person on a regular diet is 25 to 120 milliequivalents per liter per 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. Talk to your doctor about the meaning of your specific test results.

What abnormal results mean

Higher than normal urine potassium levels may be due to:

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

Low urine potassium levels may be due to the use of glucocorticoids or nonsteroidal anti-inflammatories.

Too much or too little potassium in the diet may also affect test results.

What the risks are

There are no risks.

References

Bazari H. Approach to the patient with renal disease. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 115.