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. But 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.

Why It Is Done

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.

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 form(What is a PDF document?).