Potassium - urine

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-inflammatory drugs (NSAIDs)

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 Results

The usual range for a person on a regular diet is 25 to 125 milliequivalents per liter per day. However, lower or higher urinary levels may occur depending on the amount of potassium in your diet and the amount of potassium in the body.

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 doctor about the meaning of your specific test results.

What Abnormal Results Mean

High 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 blood magnesium levels (hypomagnesemia)
• Hyperaldosteronism (very rare)
• Renal tubular acidosis
• Use of non-potassium-sparing diuretics

Low urine potassium levels may be due to:

• Adrenal gland insufficiency
• Hypoaldosteronism
• Certain medications, including beta blockers, lithium, trimethoprim, potassium-sparing diuretics, or nonsteroidal anti-inflammatory drugs (NSAIDs)

Alternative Names

Urine potassium

References

Landry DW, Bazari H. Approach to the patient with renal disease. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 116.

Update Date: 8/21/2011

Updated by: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.