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 the amount of fluids 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. You can usually get most of the potassium that you need from the foods that you eat.

Almost all of your body's potassium is inside your cells, but a small amount is in your blood. Your kidneys remove potassium in your urine (pee) to help keep the right amount of potassium in your blood. Potassium levels that are too high or too low may be a sign of a medical condition and may cause serious health issues.

Why this test is done

Your health care provider may order a potassium blood test as part of your routine 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)
• Fatigue
• Muscle weakness
• Nausea
• Numbness or tingling

If your potassium levels are too low (hypokalemia), your symptoms may include:

• Irregular heartbeat
• Muscle cramps
• Weak or twitching muscles
• Fatigue
• Nausea
• Constipation

How to prepare

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.

Sample type

Blood

Other names for this test

potassium serum, serum potassium, serum electrolytes, K