Potassium Blood Test
Reviewed
A potassium blood test measures the amount of potassium in your blood. Potassium is an electrolyte that helps control fluid balance, acid-base balance, muscle and nerve activity, and heart function. The test is often part of a routine electrolyte panel and is used to monitor or diagnose conditions related to abnormal potassium levels, such as kidney disease, high blood pressure, and heart disease.
Preparation and collection
No special preparation is needed for a potassium blood test alone. If other tests are ordered on the same sample, you may need to fast (not eat or drink) for several hours before the test. Do not eat natural black licorice for at least two weeks before the test. Avoid repeated fist clenching during the blood draw.
Understanding this test
Use the reference interval and units printed by the laboratory that performed the test. A result outside that interval is not a diagnosis by itself, and a result inside it does not rule out every condition. Your symptoms, history, medicines, timing, and related tests can change what the result means.
- Repeated clenching and relaxing of your fist just before or during the blood draw may temporarily increase potassium levels and lead to an incorrect result.
- Eating natural black licorice (not common in the U.S.) within two weeks before the test may lower potassium levels.
- Certain prescription and over-the-counter medicines and supplements can affect potassium levels.
What to do next
To learn what your results mean, talk with your provider. Your provider will interpret your results based on your health status, medications, and other factors.