Low Potassium (Hypokalemia)

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What is low potassium (hypokalemia)?

Hypokalemia—or low potassium—occurs when blood levels of potassium are lower than normal. Normal potassium values can vary somewhat from one lab to another. When a lab reports a potassium level, it will provide a reference range along with it. This is the normal range for potassium levels at that lab. Generally, a normal potassium level is between 3.6 and 5.2 mEq/L (the lab may express it as mmoles/L).

Potassium is an electrolyte and mineral you get from food in your diet. It plays an important role in nerve and muscle cell function. Like other muscles in your body, your heart muscle needs potassium to work properly. Low potassium levels can interfere with the heart and cause abnormal heart rhythms. Other hypokalemia symptoms include fatigue, weakness, muscle cramps, and constipation. Mild cases may not have any symptoms.

The most common cause of low potassium is excessive potassium loss through the urine or digestive tract. The risk of this increases for people on diuretics or with prolonged vomiting or diarrhea. Eating disorders and laxative overuse can also increase the risk of low potassium.

Hypokalemia treatment depends on the severity of the problem and the underlying cause. Mild depletions may only require a potassium-rich diet. Potassium supplements can help people who need more than they can get from diet alone. Very low potassium levels require immediate medical treatment with an IV (intravenous) potassium solution.

Low potassium usually shows up on a blood test. Doctors may order a potassium level as part of routine care or if you have an illness or take diuretics. When symptoms develop, it can become life threatening. Seek immediate medical care (call 911) if you develop heart palpitations, confusion, paralysis, excessive thirst or urination, or any other symptoms of low potassium.

What are the symptoms of low potassium?

Mild decreases in potassium levels usually do not cause any symptoms. When symptoms develop, they are nonspecific, meaning there can be several different causes of them.

Common symptoms

Common symptoms of low potassium include:

  • Fatigue

Serious symptoms that might indicate a life-threatening condition

In severe cases, low potassium can be life threatening. Seek immediate medical care (call 911) if you, or someone you are with, have any of these life-threatening symptoms including:

  • Excessive thirst or urination
  • Heart palpitations or skipping heartbeats
  • Paralysis
  • Slow breathing or difficulty breathing

Seeing your doctor regularly can help identify problems before they become serious. Routine lab tests, such as a basic metabolic panel or chemistry panel, will include potassium levels. Most people get these lab tests as part of an annual exam. If you take medicines that can lower your potassium, your doctor will likely check your labs more often.

What causes low potassium?

Among the causes of hypokalemia, losing too much potassium in the urine or from the digestive tract is the most common. This can be linked to digestive illness, certain drugs, Cushing syndrome, or low levels of magnesium in the blood. In rare cases, low potassium is due to inadequate dietary intake.

What are the risk factors for low potassium?

Several factors increase the risk of developing low potassium. Your risk is higher if you have any of the following risk factors:

  • Diuretic therapy with drugs that do not conserve potassium
  • Excessive alcohol use or abuse
  • Overuse or abuse of laxatives
  • Prolonged or excessive diarrhea or vomiting

Reducing your risk of hypokalemia

You may be able to decrease your risk of low potassium by:

  • Avoiding excessive use of alcohol and laxatives
  • Drinking electrolyte replacement solutions during periods of diarrhea or vomiting
  • Eating potassium-rich foods, such as bananas, beans, dark leafy greens, fish, nuts, and tomatoes and tomato products
  • Switching diuretics to one that preserves potassium levels

If you are at risk of low potassium, your doctor will monitor your levels on a regular basis. Spotting changes early allows your doctor to adjust your care plan and avoid problems.

How is low potassium treated?

Low potassium treatment depends on how low the levels are and the underlying cause. Mild cases of low potassium may not require any treatment. Or, treatment may only involve increasing dietary intake of potassium-rich foods, such as bananas, orange juice, potatoes, squash and spinach.

If potassium levels are low enough to cause concern, doctors may recommend a potassium supplement. Do not start a potassium supplement without talking to your doctor first.

When a diuretic could be the cause, doctors may recommend changing to a potassium-sparing diuretic. These drugs promote urination to get rid of excess fluid, but help the body hold on to potassium. You usually do not need a potassium supplement with a potassium-sparing diuretic. If it isn’t possible to switch drugs, doctors may suggest a potassium supplement.

Very low potassium levels, lower than 2.5 mEq/L require immediate medical care. Treatment usually involves an IV infusion containing potassium to quickly restore normal levels.

What are the potential complications of low potassium?

Often, low potassium is mild and doesn’t cause many symptoms or problems. These cases usually resolve without issues once doctors identify and address the problem. However, severe cases can be serious and lead to paralysis and heart problems, which are potentially fatal.

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2020 Jan 23
  1. Diuretics. Mayo Foundation for Medical Education and Research. https://www.mayoclinic.org/diseases-conditions/high-blood-pressure/in-depth/diuretics/art-20048129 
  2. Hypokalemia. Merck Manual Professional Version. https://www.merckmanuals.com/professional/endocrine-and-metabolic-disorders/electrolyte-disorders/hypokalemia 
  3. Hypokalemia. National Organization for Rare Disorders. https://rarediseases.org/rare-diseases/hypokalemia/ 
  4. Low Blood Potassium. MedlinePlus, U.S. National Library of Medicine. https://medlineplus.gov/ency/article/000479.htm 
  5. Low Potassium (Hypokalemia). Mayo Foundation for Medical Education and Research. https://www.mayoclinic.org/symptoms/low-potassium/basics/definition/sym-20050632 
  6. Low Potassium Levels in Your Blood (Hypokalemia). Cleveland Clinic. https://my.clevelandclinic.org/health/diseases/17740-low-potassium-levels-in-your-blood-hypokalemia 


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