Potassium Test

Written by Ann Pietrangelo
Medically Reviewed by George Krucik, MD

What Is a Potassium Test?

A potassium test is used to measure the amount of potassium in your blood. Potassium helps to move waste out of cells and nutrients into cells. This electrolyte is essential to proper muscle and nerve function. Even minor increases or decreases in the amount of potassium in your blood can result in serious health problems.

Your doctor may order a potassium test as part of a routine physical check-up, or if he or she suspects an electrolyte imbalance. Potassium is an electrolyte. An electrolyte becomes an ion when it is in a solution. Electrolytes conduct electricity and are important for our cells and organs to function normally.

The test is performed as a simple blood test and carries few risks or side effects. The blood sample will be sent to a laboratory for analysis and your doctor will go over the results with you.

Why a Potassium Test Is Performed

A potassium test is often performed as part of a basic metabolic panel (a group of chemical tests of your blood serum). Your doctor may order a potassium test during a routine physical or for a variety of other reasons, including:

  • checking for or monitoring an electrolyte imbalance
  • monitoring certain medications that affect potassium levels, particularly diuretics, heart medications, and high blood pressure medications
  • diagnosing heart problems and high blood pressure
  • diagnosing or monitoring kidney disease
  • checking for metabolic acidosis (when the kidneys don’t remove enough acid from the body or when the body produces too much acid, as might happen in uncontrolled diabetes)
  • diagnosing alkalosis (a condition in which the body fluids have excess alkali)
  • finding the cause of a paralysis attack

The test will help reveal whether or not your potassium level is normal.

How a Potassium Test Is Performed

Prior to the test, your doctor may want you to stop taking any medications that could affect the test results. Ask your doctor for specific instructions prior to test day.

The potassium test is performed like other routine blood tests. A site on your arm, usually the inside of your elbow or the back of your hand, will be cleaned with antiseptic. Your health care provider will wrap a band around your upper arm to create pressure so that your veins swell.

A needle will be inserted into your vein. You may feel a sting or the prick of the needle. Blood will then be collected into a tube. The band and the needle will then be removed and the site covered with a small bandage. The test generally takes only a few minutes.

Risks and side effects of a potassium test are the same as for any routine blood test. In some cases, your health care provider may have trouble entering a suitable vein. In rare instances, bleeding, bruising, lightheadedness, and fainting are reported. Anytime the skin is broken, you also run a small risk of infection.

What the Results of a Potassium Test Mean

Your body needs potassium to function normally. It is vital to the functioning of nerve and muscle cells. A normal potassium level is between 3.6 and 5.2 millimoles per liter (mmol/L). It is important to note that individual laboratories may use different values. For that reason, you should ask your doctor to interpret your specific results.

The amount of potassium in your blood is so small that tiny increases or decreases can cause serious problems.

Low Potassium Levels (Hypokalemia)

Lower-than-normal levels of potassium can be due to:

  • not enough potassium in your diet
  • gastrointestinal disorders, chronic diarrhea, vomiting
  • use of diuretics
  • certain medications (such as corticosteroids, some antibiotics, antifungals)
  • an overdose of acetaminophen
  • diabetes (particularly after taking insulin)
  • renal artery stenosis (narrowing of arteries that carry blood to the kidneys)
  • hyperkalemic periodic paralysis (episodes of muscle weakness)
  • hyperaldosteronism (adrenal gland releases too much of the hormone aldosterone)

In rare cases, low levels of potassium can be due to:

  • Cushing syndrome (when your body is exposed to high levels of the hormone cortisol, or if you take certain steroid hormones)
  • renal tubular acidosis (when the kidneys can’t adequately remove acids from your urine, resulting in too much acid in the blood)

High Potassium Levels (Hyperkalemia)

A blood potassium level of 7.0 mmol/L or higher can be life-threatening. Higher-than-normal levels of potassium may be the result of:

  • too much potassium in your diet
  • some medications (such as non-steroidal anti-inflammatory drugs (NSAIDS), beta blockers, enzyme inhibitors, and diuretics)
  • a blood transfusion
  • red blood cell destruction
  • tissue injury
  • infection
  • diabetes
  • dehydration
  • respiratory acidosis (Lungs cannot get rid of carbon dioxide produced by the body, causing fluids to become too acidic.)
  • metabolic acidosis (The body produces too much acid or the kidneys are cannot remove enough acid from the body.)
  • hyperkalemic periodic paralysis (episodes of muscle weakness)
  • kidney failure

In rare instances, high levels of potassium in the blood can be caused by:

  • Addison’s disease (The adrenal glands do not produce enough hormones.)
  • hypoaldosteronism (a condition where there isa deficiency or impaired function of the hormone aldosterone)

False Results

False results of a potassium test can occur during the collection and processing of the blood sample. For example, your potassium levels may rise if you relax and clench your fist while blood is being collected. A delay in transporting the sample to the laboratory or shaking the sample may cause potassium to leak out of the cells and into the serum.

If your doctor suspects a false result, he or she may need to have you repeat the test.

Potassium in Your Diet

You should be able to get the right amount of potassium from your diet. How much potassium you should take depends on your age, gender, and specific health conditions. The following is a general guideline provided by the Institute of Medicine. (http://iom.edu/). Ask your doctor what potassium levels are right for you.

AGE GRAMS PER DAY

0-6 months

.4

7-12 months

.7

1-3 years

3.0

4-8 years

3.8

9-13

4.5

14-18

4,7

19 and older

4.7

Breastfeeding mother

5.1

Some excellent dietary sources of potassium are:

  • Swiss chard
  • Lima beans
  • Kidney beans
  • Sweet potatoes and white potatoes (especially the skins)
  • Spinach
  • Papaya
  • Pinto beans
  • Bananas
  • Lentils
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