Dangers of Low Potassium (Hypokalemia)

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Potassium is a vital mineral that aids in nerve function, including the nerves that control heart rhythm. If potassium levels in the blood get too low, you can develop an abnormal heart rhythm or even have a heart attack or sudden cardiac arrest. Most people will never experience potassium levels that low, but some people face a higher risk than others of developing low potassium (hypokalemia). Learn what to do if you suspect low potassium levels are causing symptoms.

The Role of Potassium in the Body

Potassium performs several functions within your body, including:

  • Helps nerves work properly, including the nerves that control your heartbeat and respiration

  • Helps muscles contract, including your heart muscle

  • Transports nutrients into cells

  • Transports waste products out of cells

Potassium’s most important role involves regulating the heart’s rhythm and contractions, which is why one of the dangers of low potassium is an arrhythmia. If a doctor suspects you may be hypokalemic, he or she will order blood tests to check your potassium levels and may also order an electrocardiogram (ECG) to check for an abnormal heart rhythm.

Risk Factors for Hypokalemia

Although anyone, of any age, can develop dangerously low potassium, most people maintain adequate potassium levels in their blood throughout their lifetime. Hypokalemia most often occurs in people who take prescription diuretics (water pills) for conditions like high blood pressure or kidney disease. But you can develop hypokalemia due to excessive diarrhea or vomiting

Other risk factors include:

  • Eating disorders, including bulimia

  • Low blood magnesium levels

  • Medical conditions like hyperaldosteronism or genetic disorders like Bartter syndrome

  • Taking certain antibiotics

  • Using over-the-counter diuretics and laxatives excessively

Hypokalemia Signs and Symptoms

Because extremely low potassium can cause heart rhythm disturbances, you should be vigilant about watching for signs and symptoms of low potassium in someone who falls into one of the high-risk groups mentioned above. People with hypokalemia may experience:

In infants, hypokalemia can result from dehydration caused by diarrhea or vomiting and may present as dystonia (muscle ‘floppiness’ when you pick your baby up) and difficulty breathing. Dehydration in infants is a medical emergency, and you should call 911 for these symptoms.

Hypokalemia Diagnosis and Treatment

If your doctor suspects you have low potassium levels, he or she will first obtain tests of your blood to measure the amount of potassium circulating in your body. Normal blood potassium levels range from 3.6 to 5.2 millimoles (mmol) per liter (L) of blood. Your doctor also may obtain an ECG for hypokalemia to look for heart arrhythmias. 

A serum (blood) potassium level below 2.5 mmol/L is a medical emergency because it can lead to cardiac arrest and death. The patient will be treated in the hospital with immediate infusions of potassium through an intravenous (IV) line, along with potential other treatments to stabilize the heart rhythm. 

For low potassium levels that are not considered critical, your doctor may recommend other hypokalemia treatments, including:

  • Changing your prescription medicine for high blood pressure, heart failure, or kidney disease to a drug that helps your body retain more potassium

  • Increasing your consumption of potassium-rich foods, such as bananas, sweet potatoes, poultry, and tomatoes

  • Potassium supplements, which normally should be taken only on the advice of a physician

  • Using table salt substitute products that contain mostly potassium instead of sodium

Too Much Potassium is Dangerous Too

Eating potassium-rich foods is an excellent way to help ensure your body always has enough potassium. Foods deliver potassium slowly to the body, since the foods must go through the digestive process to extract the mineral and release it into the bloodstream. It’s difficult to get too much potassium through your diet because you would have to eat enormous quantities of food to ‘overdose’ on the mineral.

Potassium supplements, on the other hand, deliver a large dose of potassium directly to the bloodstream each time you take them. This can lead to another dangerous condition called hyperkalemia, which is too much potassium in the body. Hyperkalemia can cause heart rhythm problems and fluid imbalances that affect kidney function. Always use caution when taking potassium supplements without a doctor’s supervision.

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2020 Jan 15
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  3. Low Potassium (Hypokalemia). Mayo Clinic. https://www.mayoclinic.org/symptoms/low-potassium/basics/definition/SYM-20050632?p=1
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  6. Electrolyte Imbalances--Part 2: Potassium Balance Disorders. EMS World. https://www.emsworld.com/article/10218948/electrolyte-imbalances-part-2-potassium-balance-disorders
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