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Potassium (K) in Urine

Test Overview

A potassium test measures how much potassium is in the urine. Potassium is both an electrolyte and a mineral. It helps balance the amounts of water and electrolytes in the body. (Water is the amount of fluid inside and outside the body's cells.) It 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. When sodium levels go down, potassium levels go up. These levels are also affected by a hormone called aldosterone. This hormone is made by the adrenal glands.

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

Many foods are rich in potassium. Some examples are potatoes, bananas, prunes, orange juice, and winter squash. A balanced diet has enough potassium for the body's needs. But if your levels get low, it can take some time for your body to start holding on to potassium.

A potassium level that is too high or too low can be serious. Abnormal levels may cause symptoms such as muscle cramps or weakness, nausea, diarrhea, or frequent urination. Other symptoms may include 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 or high blood potassium test result.

How To Prepare

You do not need to do anything special to prepare for this test.

Talk to your doctor if you have any concerns about 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 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. This marks the start of your 24-hour collection period.
  • For the next 24 hours, collect all your urine. Your doctor or lab will usually give you 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. 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

It is not painful to collect a one-time or 24-hour urine sample.

Risks

Collecting a one-time or 24-hour urine sample does not cause problems.

Results

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

Normal

These numbers are just a guide. The range for "normal" varies from lab to lab. Your lab report should show what range your lab uses for "normal." Also, your doctor will evaluate your results based on your health and other factors. So a number that is outside the normal range here may still be normal for you.

Results are ready in 1 day.

Potassium in urine in a 24-hour samplefootnote 1

Normal (adults):

25-125 milliequivalents (mEq) per day (24 hours) or 25-125 millimoles (mmol) per day (24 hours)

Normal (children):

10-60 mEq per day (24 hours) or 10-60 mmol per day (24 hours)

Many conditions can affect potassium levels. Your doctor will talk with you about any abnormal results as they relate to your symptoms and past health.

What Affects the Test

You may not be able to have the test, or the results may not be helpful, if:

  • You take potassium supplements.
  • You take certain medicines, such as antibiotics that contain potassium (such as a type of penicillin g). Other medicines that can affect the results are nonsteroidal anti-inflammatory drugs (NSAIDs), heparin, insulin, glucose, corticosteroids, diuretics, and medicines used to treat high blood pressure and heart disease. Natural licorice ( Glycyrrhiza glabra) may also affect the results.
  • You use too many laxatives.
  • You have severe vomiting.
  • You don't collect exactly 24 hours of urine.

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 if conditions or medicines may be causing fluid or electrolyte imbalances. Urine potassium levels are often high when blood levels are low. Or they may be low when blood levels are high. These 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

ByHealthwise Staff
Primary Medical Reviewer Adam Husney, MD - Family Medicine
E. Gregory Thompson, MD - Internal Medicine
Martin J. Gabica, MD - Family Medicine

Current as ofOctober 9, 2017

Current as of: October 9, 2017

Author: Healthwise Staff

Medical Review: Adam Husney, MD - Family Medicine & E. Gregory Thompson, MD - Internal Medicine & Martin J. Gabica, MD - Family Medicine