What is a Potassium Blood Test?
A potassium blood test measures the amount of potassium in your blood. Potassium is a type of electrolyte. Electrolytes are electrically charged minerals that help control fluid levels and the balance of acids and bases (pH balance) in your body. They also help control muscle and nerve activity and perform other important functions.
Your cells, nerves, heart, and muscles need potassium to work properly. Potassium levels that are too high or too low may be a sign of a medical problem.
Other names: potassium serum, serum potassium, serum electrolytes, K
What is it used for?
A potassium blood test measures how much potassium is in your blood. The test is often part of a group of routine blood tests called an electrolyte panel. It may be used to monitor or diagnose conditions related to abnormal potassium levels. These conditions include kidney disease, high blood pressure, and heart disease.
Why do I need a potassium blood test?
Your health care provider may order a potassium blood test as part of your regular checkup or to monitor an existing condition, such as diabetes, kidney disease, or adrenal gland disorders. You may also need this test if you take medicines that could affect your potassium levels or if you have symptoms of having too much or too little potassium.
If your potassium levels are too high (hyperkalemia), your symptoms may include:
- Arrhythmia (a problem with the rate or rhythm of your heartbeat)
- Muscle weakness
- Numbness or tingling
If your potassium levels are too low (hypokalemia), your symptoms may include:
What happens during a potassium blood test?
A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.
Will I need to do anything to prepare for the test?
You don't need any special preparations for a potassium blood test or an electrolyte panel. If your provider has ordered more tests on your blood sample, you may need to fast (not eat or drink) for several hours before the test. Your provider will let you know if there are any special instructions to follow.
Are there any risks to the test?
There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.
What do the results mean?
Too much potassium in the blood (hyperkalemia). It's often the result of two or more causes. High potassium levels may be a sign of:
- Kidney disease. Your kidneys remove extra potassium from your body. Too much potassium may mean your kidneys aren't working well.
- Addison disease, a disorder of the adrenal glands
- Injuries, burns, or surgery that can cause your cells to release extra potassium into your blood
- Type 1 diabetes that is not well controlled
- The side effects of certain medicines, such as diuretics ("water pills") or antibiotics
- A diet too high in potassium (not common). Bananas, apricots, green leafy vegetables, avocados and many other foods are good sources of potassium that are part of a healthy diet. But eating very large amounts of potassium-rich foods or taking potassium supplements can lead to health problems.
Too little potassium in the blood (hypokalemia) may be a sign of:
- Use of prescription diuretics
- Fluid loss from diarrhea, vomiting, or heavy sweating
- Using too many laxatives
- Adrenal gland disorders, including Cushing's syndrome and aldosteronism
- Kidney disease
- Alcohol use disorder (AUD)
- A diet too low in potassium (not common)
If your test results are not in the normal range, it doesn't always mean that you have a medical condition that needs treatment. Certain prescription and over-the-counter medicines and supplements may raise your potassium levels. And eating a lot of licorice may lower your levels. But only real licorice, which comes from licorice plants, has this effect. Most licorice products sold in the U.S. don't contain any real licorice. Check the package ingredient label to be sure.
To learn what your results mean, talk with your provider.
Learn more about laboratory tests, references ranges, understanding results.
Is there anything else I need to know about a potassium blood test?
Repeated clenching and relaxing of your fist just before or during your blood test may temporarily increase the potassium levels in your blood. This may lead to an incorrect result.
- FDA: US Food and Drug Administration [Internet]. Silver Spring (MD): US Department of Health and Human Services; Black Licorice: Trick or Treat?; [current as of 2017 Nov 6; cited 2022 Mar 13]; [about 3 screens]. Available from: https://www.fda.gov/consumers/consumer-updates/black-licorice-trick-or-treat
- Hinkle J, Cheever K. Brunner & Suddarth's Handbook of Laboratory and Diagnostic Tests. 2nd Ed, Kindle. Philadelphia: Wolters Kluwer Health, Lippincott Williams & Wilkins; c2014. Potassium, Serum; 426–27 p.
- Mayo Clinic [Internet]. Mayo Foundation for Medical Education and Research; c1998–2022. High potassium (hyperkalemia); [cited 2022 Feb 28]; [about 3 screens]. Available from: https://www.mayoclinic.org/symptoms/hyperkalemia/basics/definition/sym-20050776
- Mayo Clinic [Internet]. Mayo Foundation for Medical Education and Research; c1998–2022. Low potassium (hypokalemia); [cited 2022 Feb 28]; [about 3 screens]. Available from: https://www.mayoclinic.org/symptoms/low-potassium/basics/definition/sym-20050632
- Merck Manual Consumer Version [Internet]. Kenilworth (NJ): Merck & Co., Inc.; c2022. Addison Disease (Primary or Chronic Adrenocortical Insufficiency) [modified 2020 Oct; cited 2022 Feb 82]; [about 4 screens]. Available from: https://www.merckmanuals.com/home/hormonal-and-metabolic-disorders/adrenal-gland-disorders/addison-disease
- Merck Manual Consumer Version [Internet]. Kenilworth (NJ): Merck & Co., Inc.; c2022. Hyperkalemia (High Level of Potassium in the Blood) [modified 2021; cited cited 2022 Feb 28]; [about 3 screens]. Available from: http://www.merckmanuals.com/home/hormonal-and-metabolic-disorders/electrolyte-balance/hyperkalemia-high-level-of-potassium-in-the-blood
- Merck Manual Consumer Version [Internet]. Kenilworth (NJ): Merck & Co., Inc.; c2022. Hypokalemia (Low Level of Potassium in the Blood) modified 2021 Oct; cited 2022 Feb28]; [about 3 screens]. Available from: http://www.merckmanuals.com/home/hormonal-and-metabolic-disorders/electrolyte-balance/hypokalemia-low-level-of-potassium-in-the-blood
- Merck Manual Consumer Version [Internet]. Kenilworth (NJ Merck & Co., Inc.; c2022. Overview of Potassium's Role in the Body [modified 2021 Oct; cited 2022 Feb 28]; [about 2 screens]. Available from: http://www.merckmanuals.com/home/hormonal-and-metabolic-disorders/electrolyte-balance/overview-of-potassium-s-role-in-the-body
- National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; Blood Tests [updated 2022 Mar 24; cited 2022 Feb 28]; [about 5 screens]. Available from: https://www.nhlbi.nih.gov/health/blood-tests
- National Kidney Foundation [Internet]. New York: National Kidney Foundation Inc., c2022. A to Z Health Guide: Understanding Lab Values [cited 2022 Feb 28]; [about 5 screens]. Available from: https://www.kidney.org/atoz/content/understanding-your-lab-values
- National Kidney Foundation [Internet]. New York: National Kidney Foundation Inc., c2022. Potassium and Your CKD Diet [cited 2022 Feb 28]; [about 7 screens]. Available from: https://www.kidney.org/atoz/content/potassium
- NIH U.S. National Library of Medicine: Genetics Home Reference [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; hyperkalemic periodic paralysis; [updated 2020 Aug 18; cited 2022 Feb 28]; [about 6 screens]. Available from: https://ghr.nlm.nih.gov/condition/hyperkalemic-periodic-paralysis
- NIH U.S. National Library of Medicine: Genetics Home Reference [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; hypokalemic periodic paralysis; [updated 2021 Apr 7; cited 2022 Feb 28]; [about 6 screens]. Available from: https://medlineplus.gov/genetics/condition/hypokalemic-periodic-paralysis/
- Testing.com [Internet]. Seattle (WA): OneCare Media; c2022. Potassium [modified 2021 Nov 9; cited 2022 Feb 28]; [about 15 screens]. Available from: https://www.testing.com/tests/potassium/
- University of Rochester Medical Center [Internet]. Rochester (NY): University of Rochester Medical Center; c2022. Health Encyclopedia: Potassium [cited 2022 Feb 28]; [about 4 screens]. Available from: https://www.urmc.rochester.edu/encyclopedia/content.aspx?contenttypeid=167&contentid=potassium