Test Overview

A potassium test measures how much potassium is in the urine. This test can also be done to help determine the cause of high or low potassium levels in the blood. 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.

A potassium level that is too high or too low can be serious. Abnormal levels in the blood 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

• In general, there's nothing you have to do before this test, unless your doctor tells you to.
• For 24-hour urine collection, your doctor or lab will usually give you a large container that holds about 4 litres (1 gallon).

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 4 litres (1 gallon). The container may have 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

This test usually doesn't cause any pain or discomfort.

Risks

There is very little chance of having a problem from this test.

Results

Each lab has a different range for what's normal. Your lab report should show the range that your lab uses for each test. The normal range is just a guide. Your doctor will also look at your results based on your age, health, and other factors. A value that isn't in the normal range may still be normal for you.

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.