Potassium (K) in Urine

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. 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, including 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. However, potassium is passed in the urine even if the level in the body is low so the level of potassium can get lower.

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.

A urine test to check potassium levels is done to:

• Check levels in people being treated with medicines, such as diuretics and for people having kidney dialysis.
• Check how well the kidneys are working.
• Check to see whether treatment for low or high potassium levels is working.
• Check people with high blood pressure who may have a problem with their kidneys or adrenal glands.
• Check the effects of extra nutrition (total parenteral nutrition [TPN]) on potassium levels.
• Check to see whether certain cancer treatments are causing too many cells to be destroyed (cell lysis). Cell lysis syndrome causes very high levels of some electrolytes, including potassium.

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

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

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

Clean-catch midstream one-time urine collection

• Wash your hands to make sure they are clean before collecting the urine.
• If the collection cup has a lid, remove it carefully and 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 retract 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 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 is not wiped across the urethra.
• Begin 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 several seconds, place the collection cup into the urine stream and collect about 2 fl oz (59 mL) 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 cannot 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 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.

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

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

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

Normal results may vary from lab to lab. Results are ready in 1 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 medical history.

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

• Taking potassium supplements.
• Taking medicines, such as antibiotics that contain potassium (such as a type of penicillin g), nonsteroidal anti-inflammatory drugs (NSAIDs), heparin, insulin, glucose, corticosteroids, diuretics, medicines used to treat high blood pressure and heart disease, and natural licorice (Glycyrrhiza glabra).
• The overuse of laxatives.
• Severe vomiting.
• Failing to collect exactly 24 hours of urine.

• Potassium levels can also be checked in a blood test. For more information, see the medical test 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.

Other Works Consulted

• Chernecky CC, Berger BJ, eds. (2004). Laboratory Tests and Diagnostic Procedures, 4th ed. Philadelphia: Saunders.

• Pagana KD, Pagana TJ (2006). Mosby’s Manual of Diagnostic and Laboratory Tests, 3rd ed. St. Louis: Mosby.