Your potassium levels can indicate underlying health conditions like high blood pressure or kidney disease. A doctor may perform a potassium blood test as part of a routine physical.

A potassium test is used to measure the amount of potassium in your blood. Potassium is an electrolyte that’s essential for 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 if they suspect you have an electrolyte imbalance or as part of a routine checkup.

Potassium is an electrolyte. Electrolytes become ions when they’re in a solution, and they conduct electricity. Our cells and organs require electrolytes to function normally.

A potassium test is performed as a simple blood test and carries few risks or side effects. The blood sample drawn will be sent to a laboratory for analysis. Your doctor will review the results with you.

A potassium test is often performed as part of a basic metabolic panel, which is a group of chemical tests run on 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 diabetes that’s not well-managed)
  • 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 your potassium level is normal.

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 your 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 healthcare professional 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 will be 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 healthcare professional may have trouble entering a suitable vein. In rare instances, people report:

  • bleeding
  • bruising
  • lightheadedness
  • fainting

Anytime the skin is broken, you also run a small risk for infection.

There are no special preparations needed before taking a blood potassium test. However, you may need to fast (not eat or drink) for a few hours before if you are having other tests done during your blood draw.

Talk to your healthcare provider for specific instructions for your case.

Your body needs potassium to function normally. It’s vital to the functioning of nerve and muscle cells.

A normal potassium level is between 3.6 and 5.2 millimoles per liter. It’s 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 some diuretics
  • excessive laxative use
  • excessive sweating
  • folic acid deficiency
  • certain medications, such as corticosteroids, some antibiotics, and antifungals
  • an overdose of acetaminophen
  • diabetes, particularly after taking insulin
  • chronic kidney disease
  • hyperaldosteronism (when the adrenal gland releases too much of the hormone aldosterone)
  • Cushing’s syndrome (when your body is exposed to high levels of the hormone cortisol or if you take certain steroid hormones)

High potassium levels (hyperkalemia)

A blood potassium level of 7.0 millimoles per liter or higher can be life threatening.

Having higher-than-normal levels of potassium in your blood can be the result of a variety of conditions and circumstances. These include:

  • having too much potassium in your diet or taking potassium supplements
  • taking some medications, such as nonsteroidal anti-inflammatory drugs (NSAIDs), beta-blockers, ACE enzyme inhibitors, angiotensin II receptor blockers (ARBs), and diuretics
  • receiving a blood transfusion
  • red blood cell destruction due to severe injury or burns
  • tissue injury causing a breakdown of muscle fibers
  • infection
  • type 1 diabetes
  • dehydration
  • respiratory acidosis (when the lungs can’t get rid of carbon dioxide produced by the body, causing fluids to become too acidic)
  • metabolic acidosis (when the body produces too much acid or the kidneys can’t remove enough acid from the body)
  • kidney failure
  • Addison’s disease (when the adrenal glands don’t produce enough hormones)
  • hypoaldosteronism (a condition where there’s a 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, they may need to have you repeat the test.

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. 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

A potassium test is a very common test used to check electrolyte levels. It can be ordered as part of a routine physical or to diagnose certain conditions.

Talk with your healthcare provider to determine if you might benefit from a potassium test.