This test measures the amount of potassium in the fluid portion (serum) of the blood. Potassium (K+) helps nerves and muscles communicate. It also helps move nutrients into cells and waste products out of cells.
Potassium levels in the body are mainly controlled by the hormone aldosterone.
Hypokalemia test; K+
How the test is performed
A blood sample is needed. Most of the time blood is drawn from a vein located on the inside of the elbow or the back of the hand.
How to prepare for the test
Many medicines can interfere with blood test results.
- Your health care provider will tell you if you need to stop taking any medicines before you have this test.
- Do not stop or change your medications without talking to your doctor first.
How the test will feel
You may feel slight pain or a sting when the needle is inserted. You may also feel some throbbing at the site after the blood is drawn.
Why the test is performed
This test is a regular part of a basic or comprehensive metabolic panel.
Your doctor may order this test to diagnose or monitor kidney disease. The most common cause of high potassium levels is kidney disease.
Potassium is important to heart function.
- Your doctor may order this test if you have signs of high blood pressure or heart problems.
- Small changes in potassium levels can have a big effect on the activity of nerves and muscles, especially the heart.
- Low levels of potassium can lead to an irregular heartbeat or other electrical malfunction of the heart.
- High levels cause decreased heart muscle activity.
- Either situation can lead to life-threatening heart problems.
Sometimes, the potassium test may be done in persons who are having an attack of paralysis.
The normal range is 3.7 to 5.2 mEq/L.
Note: mEq/L = milliequivalent per liter
Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.
The examples above show the common measurements for results for these tests. Some laboratories use different measurements or may test different specimens.
What abnormal results mean
High levels of potassium (hyperkalemia) may be due to:
- Addison's disease (rare)
- Blood transfusion
- Certain medications
- Crushed tissue injury
- Hyperkalemic periodic paralysis
- Hypoaldosteronism (very rare)
- Kidney failure
- Metabolic or respiratory acidosis
- Red blood cell destruction
- Too much potassium in your diet
Low levels of potassium (hypokalemia) may be due to:
- Chronic diarrhea
- Cushing syndrome (rare)
- Diuretics such as hydrochlorothiazide, furosemide, and indapamide
- Hypokalemic periodic paralysis
- Not enough potassium in the diet
- Renal artery stenosis
- Renal tubular acidosis (rare)
If it is hard to get the needle into the vein to take the blood sample, injury to the red blood cells may cause potassium to be released. This may cause a falsely high result.
Seifter JR. Potassium disorders. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 119.
Last reviewed 5/5/2013 by David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by A.D.A.M. Health Solutions, Ebix, Inc., Editorial Team: David Zieve, MD, MHA, Bethanne Black, Stephanie Slon, and Nissi Wang.
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