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Potassium (K) in Urine

Test Overview

A test for potassium in the urine is a test that checks how much potassium is in the urine. Potassium is both an electrolyte and a mineral. It helps keep the water (the amount of fluid inside and outside the body's cells) and electrolyte balance of the body. Potassium is also important in how nerves and muscles work.

Potassium levels often change with sodium levels. When sodium levels go up, potassium levels go down, and when sodium levels go down, potassium levels go up. Potassium levels are also affected by a hormone called aldosterone, which is made by the adrenal glands.

Potassium levels can be affected by how the kidneys are working, the blood pH, the amount of potassium you eat, the hormone levels in your body, severe vomiting, and taking certain medicines, such as diuretics and potassium supplements. Certain cancer treatments that destroy cancer cells can also make potassium levels high.

Many foods are rich in potassium, including scallops, potatoes, figs, bananas, prune juice, orange juice, and squash. A balanced diet has enough potassium for the body's needs. But if your potassium levels get low, it can take some time for your body to start holding on to potassium. In the meantime, potassium is still passed in the urine, so you may end up with very low levels of potassium in your body, which can be dangerous.

A potassium level that is too high or too low can be serious. Abnormal potassium levels may cause symptoms such as muscle cramps or weakness, nausea, diarrhea, frequent urination, dehydration, low blood pressure, confusion, irritability, paralysis, and changes in heart rhythm.

Why It Is Done

A urine test to check potassium levels is done to:

  • Look for the cause of a low blood potassium test result (hypokalemia).

How To Prepare

You do not need to do anything before having this test.

Talk to your doctor about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will mean. To help you understand the importance of this test, fill out the medical test information formmedical test information form(What is a PDF document?).

How It Is Done

Urine potassium can be checked in a single urine sample but it is more often measured in a 24-hour urine sample.

Urine collection over 24 hours

  • You start collecting your urine in the morning. When you first get up, empty your bladder but do not save this urine. Write down the time that you urinated to mark the beginning of your 24-hour collection period.
  • For the next 24 hours, collect all your urine. Your doctor or lab will usually provide you with a large container that holds about 1 gal (4 L). The container has a small amount of preservative in it. Urinate into a small, clean container and then pour the urine into the large container. Do not touch the inside of either container with your fingers.
  • Keep the large container in the refrigerator for the 24 hours.
  • Empty your bladder for the final time at or just before the end of the 24-hour period. Add this urine to the large container and record the time.
  • Do not get toilet paper, pubic hair, stool (feces), menstrual blood, or other foreign matter in the urine sample.

How It Feels

There is no discomfort in collecting a one-time or 24-hour urine sample.

Risks

There is no chance for problems in collecting a one-time or 24-hour urine sample.

Results

A test for potassium in the urine is a 24-hour test or a one-time (spot) test that checks how much potassium is in the urine. Potassium is both an electrolyte and a mineral.

Normal

The normal values listed here—called a reference range—are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what's normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.

Results are ready in 1 day.

Potassium in urine in a 24-hour sample1
Normal (adults):

25–125 milliequivalents per liter (mEq/L) per day or 25–125 millimoles per liter (mmol/L) per day

Normal (children):

10–60 mEq/L per day or 10–60 mmol/L per day

Many conditions can affect potassium levels. Your doctor will talk with you about any abnormal results that may be related to your symptoms and past health.

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

What To Think About

  • Potassium levels can also be checked in a blood test. To learn more, see the topic Potassium (K) in Blood.
  • Doctors may look at urine potassium and blood potassium levels to see whether conditions or medicines may be causing fluid or electrolyte imbalances. Urine potassium levels are often high when blood levels are low or low when blood levels are high. Urine potassium levels are affected by medicines and hormones.

References

Citations

  1. Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.

Other Works Consulted

  • Chernecky CC, Berger BJ (2008). Laboratory Tests and Diagnostic Procedures, 5th ed. St. Louis: Saunders.
  • Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.
  • Pagana KD, Pagana TJ (2010). Mosby’s Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.

Credits

By Healthwise Staff
Primary Medical Reviewer Adam Husney, MD - Family Medicine
Specialist Medical Reviewer Avery L. Seifert, MD - Urology
Current as of September 4, 2012

Current as of: September 4, 2012

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