Potassium is a mineral and an electrolyte that the body requires to support key processes. It plays a role in the function of the kidneys. However, having too much or too little potassium may be bad for the kidneys as it can result in complications.

Potassium plays a key role in a number of bodily processes, including nerve transmission, heart contractility, cellular transport, and normal kidney function. It is important that people get sufficient potassium from the diet, as an imbalance can cause problems in the body.

In this article, we look at the association between potassium and kidney health. We also explain how people with chronic kidney disease (CKD) can manage their dietary needs for better health.

A person looking at the potassium content of food.Share on Pinterest
d3sign/Getty Images

The kidneys are bean shaped organs that are extremely important in removing waste and maintaining a healthy balance of water, salts, and minerals, such as potassium, in the blood. Without this balance, nerves, muscles, and other tissues in the body may not work normally.

CKD is a condition that causes the loss of normal kidney function. People with diabetes or high blood pressure have a higher risk of CKD. The Centers for Disease Control and Prevention (CDC) estimate that this condition affects 15% of adults in the United States.

CKD can get worse over time, but people may be able to manage it by adhering to a healthy lifestyle and getting proper treatment for any underlying conditions.

If CKD does not improve, it can result in kidney damage, which can affect how well the kidneys manage potassium. People with very severe CKD may require a kidney transplant or dialysis.

Under normal conditions, the kidneys respond to hormones in the body to maintain a normal amount of potassium in the body. The National Institutes of Health (NIH) state that the standard amount of potassium in the blood typically ranges from 3.6 to 5.0 millimoles per liter.

In people with CKD, the improperly functioning kidneys lose the ability to filter fluids and electrolytes in the body, which can lead to dangerously high levels of potassium in the blood. Hyperkalemia is the medical term for excessively high levels of potassium.

A doctor can diagnose hyperkalemia with a blood test, and they may also order an electrocardiogram to make sure that the heart is working properly.

Hyperkalemia may not produce symptoms for some people. However, potassium levels of 6.5–7.0 milliequivalents per liter or higher can cause serious symptoms, including:

  • muscle weakness
  • muscle paralysis
  • abnormal heart rhythm
  • chest palpitations

Other possible causes of hyperkalemia besides CKD include diabetes, trauma, rhabdomyolysis, medication use, and excessive potassium intake.

To treat hyperkalemia, a doctor may recommend eating a diet with lower potassium levels or changing medications. In cases of severe hyperkalemia, they might prescribe medication to treat it.

Just as potassium levels in the body can get too high, they can also drop too low, which doctors refer to as hypokalemia. Hypokalemia is typically due to another underlying medical illness that a doctor must diagnose.

Possible causes of hypokalemia include:

  • kidney disease
  • certain medications, such as diuretics or laxatives
  • excessive vomiting or diarrhea
  • intestinal obstructions or infections

Symptoms of hypokalemia may include:

  • muscle weakness
  • metabolic acidosis
  • abnormal heart rhythm
  • constipation
  • respiratory failure

A doctor can diagnose hypokalemia using blood and urine tests. They will treat it by addressing the underlying cause, as well as replenishing potassium and fluids.

For adults, the World Health Organization (WHO) recommends a potassium intake of at least 3,510 milligrams (mg) per day, while the NIH suggests a daily intake of 2,600 mg for females and 3,400 mg for males.

In people with moderate-to-severe CKD, doctors may recommend a potassium-restricted diet of roughly 2,000 mg per day. A dietitian can advise on the specific level of restriction. People with CKD may wish to consider avoiding or limiting the consumption of high potassium foods.

Other ways to manage dietary potassium include:

  • draining and rinsing food
  • replacing salt and salt substitutes with other seasonings
  • reading all food labels carefully

When dining out, people can take steps to avoid eating too much potassium. For instance, they can choose restaurants with suitable options on the menus and even call ahead to request special dietary alterations to their preferred meal option. They can also pay close attention to their diet throughout the rest of the day.

Some examples of low potassium foods include:

  • apples, pineapples, grapes, strawberries, and cranberries
  • cauliflower, lettuce, onions, peppers, and radishes
  • pita, tortillas, white bread, and white rice
  • beef and chicken

High potassium foods include:

  • bananas, melons, oranges, raisins, prunes, and avocado
  • bran products and granola
  • beans
  • artichokes, spinach, tomatoes, plantains, and winter squash
  • brown rice and potatoes

Some individuals with CKD may find it challenging to plan meals because so many foods have high levels of potassium. However, there is a method called leaching that can lower the amount of potassium in some foods.

People can leach vegetables by cutting them and soaking them for a few hours in warm unsalted water. They can then drain the water and wash the vegetables using warm water. If they wish to cook the vegetables, they should use unsalted water.

If a person with CKD does decide to consume a meal high in potassium, it is important to try to cut down on the serving size.

Limiting potassium intake helps people with CKD lower their risk of worsening disease.

A person with CKD may be less tolerant of high sodium levels in their body. A high sodium diet can cause a large amount of fluid in the body, which can result in symptoms of swelling or shortness of breath. Doctors typically use drugs called diuretics to treat these symptoms.

People with CKD also tend to retain more hydrogen in their body.

In the body, hydrogen ions act as acids. If the kidneys are not working properly, there will be higher levels of hydrogen ions in the body. Doctors refer to this as metabolic acidosis. Individuals with metabolic acidosis may require bicarbonate supplements.

The inability of the kidneys to filter blood effectively can result in higher levels of phosphate and lower levels of calcium. This imbalance can cause bone weakness and increase the risk of heart disease and stroke.

Chronic kidney disease makes it difficult for the kidneys to function properly, and this can cause problems in the levels of nutrients, such as potassium, in the body. An imbalance of potassium in the body can cause complications relating to the muscles and the heart.

It is important for people with CKD to have regular checkups with their doctor and a dietitian to manage their potassium levels and appropriately take care of their health.