What Is High Potassium?

Medically Reviewed by Brunilda Nazario, MD on January 27, 2022
2 min read

Potassium is a key nutrient that you can get from eating foods that have it, such as bananas, oranges, and broccoli.

This nutrient is also called an "electrolyte" -- a mineral that helps your muscles and nerves communicate with each other. It keeps your heart beating regularly and your blood pressure stable.

When your body is working right, you'll get all the potassium you need from your diet. Your kidneys send any extra potassium out of your body when you pee.

When your kidneys aren't doing their job as they should, you can end up with too much potassium in your blood.

A normal potassium level for adults is between 3.5 and 5.5 millimoles per liter (mmol/L).

Your doctor will tell you that your potassium level is high (also called hyperkalemia) when it goes above 5.5 mmol/L.

If your potassium level is above 6.5 mmol/L, it's dangerously high and you need medical care right away.

Your doctor might tell you that your high potassium level is "acute." That means that with treatment, the high level only lasts a few days.

If your doctor says you have "chronic" high potassium levels, it means you'll need long-term treatment to control it. 

The most common causes of a high potassium level are:

Kidney disease. If you have a problem that makes your kidneys not work as well anymore, they may stop being able to remove potassium, which then builds up in your body.

Eating too many high-potassium foods if you have kidney disease. If you're kidneys aren't working right, your potassium levels can go up if you eat a lot of potassium-rich foods like cantaloupe, honeydew melon, oranges and orange juice, dried fruit, avocado, and bananas.  

Medications that raise potassium levels. Some medicines make it harder for your kidneys to remove potassium from your blood.

Less common causes of high potassium are:

  • Addison's disease, which can lead to problems with your kidneys
  • Taking too much extra potassium in supplements or salt substitutes
  • Serious injuries or burns, which may cause your body to release extra potassium into your blood
  • Diabetes that is not well controlled, which can make it harder for your kidneys to do their job
  • Dehydration
  • Congestive heart failure
  • HIV
  • Chemotherapy

Because potassium helps your muscles and nerves signal each other, having too much in your blood can harm your muscles, including those in your heart. This can lead to: 

Irregular heartbeats (arrhythmias). Potassium helps keep your heartbeat regular by helping to control the electrical signaling of your myocardium -- the middle layer of your heart muscle. When your potassium level is too high, it can make your heart beat too fast, too slow, or with an irregular rhythm.

Heart attack. An irregular heartbeat, left untreated, can cause a heart attack.

Muscle weakness or paralysis. It may begin in your feet and legs and then move up your body.