Potassium Test: About This Test

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What is it?

A potassium test checks how much potassium is in your blood or urine. Potassium helps keep the body's water and electrolytes in balance. It is also important in how nerves and muscles work.

Potassium levels can be tested by having a blood sample taken or by collecting your urine. Urine potassium can be checked in a single urine sample. But it is more often measured in a 24-hour urine sample.

Why is this test done?

A blood or urine test for potassium may be done to:

  • Check how well your kidneys are working.
  • Check levels if you are being treated with medicines such as diuretics or having kidney dialysis.
  • See if treatment for low or high potassium levels is working.

How can you prepare for the test?

  • You do not need to do anything before having this test.
  • Be sure to tell your doctor about all the non-prescription and prescription medicines and herbs or other natural health products you take. There are many medicines and natural health products that can affect the results of these tests.

What happens before the test?

For 24-hour urine collection, your doctor or lab will usually give you a large container that holds about 4 litres.

What happens during the test?

Blood test

A health professional takes a sample of your blood.

One-time urine collection

  • Wash your hands to make sure they are clean before you collect the urine.
  • If the collection cup has a lid, remove it carefully. Set it down with the inner surface up. Do not touch the inside of the cup with your fingers.
  • Clean the area around your genitals.
    • A man should pull back the foreskin, if present, and clean the head of his penis with medicated towelettes or swabs.
    • A woman should spread open the genital folds of skin with one hand. Then she should use her other hand to clean the area around the urethra with medicated towelettes or swabs. She should wipe the area from front to back so bacteria from the anus are not wiped across the urethra.
  • Start urinating into the toilet or urinal. A woman should hold apart the genital folds of skin while she urinates.
  • After the urine has flowed for a few seconds, place the collection cup into the urine stream. Collect about 60 millilitres of this "midstream" urine without stopping your flow of urine.
  • Do not touch the rim of the cup to your genital area. Do not get toilet paper, pubic hair, stool (feces), menstrual blood, or anything else in the urine sample.
  • Finish urinating into the toilet or urinal.
  • Carefully replace and tighten the lid on the cup. Then return it to the lab. If you are collecting the urine at home and can't get it to the lab in an hour, refrigerate it.

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 beginning of your 24-hour collection period.
  • For the next 24 hours, collect all your urine. The large container from your doctor or lab has a small amount of preservative in it. Urinate into a small, clean cup, and then pour the urine into the large container. Do not touch the inside of the container or the cup 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 long does the test take?

  • A blood test or one-time urine collection will probably take a few minutes. Or you may collect your urine over a period of 24 hours.

What happens after the test?

After a blood test:

  • You will probably be able to go home right away.
  • You can go back to your usual activities right away.

After a urine test, you will need to return the urine sample to the lab or the doctor's office.

When should you call for help?

Watch closely for changes in your health, and be sure to contact your doctor or nurse call line if you have questions about the test.

Follow-up care is a key part of your treatment and safety. Be sure to make and go to all appointments, and call your doctor or nurse call line if you are having problems. It's also a good idea to keep a list of the medicines you take. Ask your doctor when you can expect to have your test results.

Where can you learn more?

Go to https://www.healthwise.net/patientEd

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Current as of: October 9, 2017