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Potassium test

Hypokalemia test; K+

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.

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Blood test

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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.

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.

You may have 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.

It may also be done if your provider suspects metabolic acidosis (for example, caused by uncontrolled diabetes) or alkalosis (for example, caused by excess vomiting).

Sometimes, the potassium test may be done in people who are having an attack of paralysis.

Normal Results

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 provider 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:

Low levels of potassium (hypokalemia) may be due to:

Considerations

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.

Related Information

Ions
Aldosterone blood test
Metabolic acidosis
Alkalosis
Heart palpitations
High potassium level
Acute kidney failure
Respiratory acidosis
Hyperkalemic periodic paralysis
Addison disease
Low potassium level
Hyperaldosteronism - primary and secondary
Hypokalemic periodic paralysis
Cushing syndrome
Proximal renal tubular acidosis
Acute adrenal crisis
Acute nephritic syndrome
Bulimia
Chronic kidney disease
Cushing disease
Cushing syndrome due to adrenal tumor
Exogenous Cushing syndrome
Ectopic Cushing syndrome
Diabetic ketoacidosis
Distal renal tubular acidosis
Rhabdomyolysis
Thyrotoxic periodic paralysis

References

Seifter JR. Potassium disorders. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 25th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 117.

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Review Date: 5/3/2015  

Reviewed By: Laura J. Martin, MD, MPH, ABIM Board Certified in Internal Medicine and Hospice and Palliative Medicine, Atlanta, GA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.

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