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What causes low potassium?

You’ve undoubtedly heard that an apple a day keeps the doctor away. But what about a banana a day? Your body needs potassium to function. It is one of the essential minerals for health. It helps regulate your body’s fluid balance, maintains your body’s electrolyte system, reduces blood pressure, and lowers your risk of stroke. 

However, when it comes to potassium, balance matters. 

Too much potassium, called hyperkalemia, can cause weakness, fatigue, loss of muscle function, and slowed heartbeat. Too little potassium, called hypokalemia, can cause muscle weakness, muscle twitches, heart palpitations, and cramps—it can also lead to paralysis and respiratory failure.

Low levels of potassium can cause serious health problems, like high blood pressure and kidney stones, which is why it’s helpful to know how to identify the symptoms of low potassium and what could be causing it. Fortunately, you can often raise potassium levels on your own through diet and supplementation. Here’s what you need to know.

What is considered low potassium?

Low potassium levels are blood potassium levels under 3.5 mEq/L; under 2.5 mEq/L can be life-threatening. Normal potassium levels, for most people, are typically between 3.5 and 5.0 mEq per liter (mEq/L), according to a 2018 clinical update. Anything above 5.0 mEq/L is considered high, and levels above 6.0 can be dangerous and might require immediate medical attention. 

Note: Hypokalemia is uncommon in people with normal kidney function. 

Most people don’t go to the doctor for a low level of potassium or because they think they are hypokalemic. Usually, it is detected when you are having blood work done because you have symptoms of another illness, such as an adrenal disorder, or when you have routine lab work done, which is often necessary if you take a diuretic. 

What are some symptoms of low potassium?

Many people do not experience any symptoms of hypokalemia until it is severe, and the amount of potassium has dropped below 3.0 mEq/L.

People with moderate potassium deficiency might experience: 

  • Constipation
  • Muscle weakness
  • Fatigue
  • A general feeling of malaise

Severe potassium deficiency symptoms include:

  • Muscle twitches
  • Muscle cramps
  • Muscle weakness
  • Paralysis
  • Abnormal heart rhythms or palpitations
  • Kidney problems
  • Loss of appetite, nausea, and vomiting
  • Bloating and constipation
  • Fatigue
  • Tingling or numbness
  • High blood pressure
  • Fainting

How is hypokalemia diagnosed?

Low potassium is not an illness in itself, but rather is a symptom of an underlying condition or disease. When low potassium is detected, your doctor might suggest additional testing to determine the cause. Further blood tests might check for glucose, magnesium, calcium, sodium, phosphorus, thyroid hormones, and aldosterone. Your doctor might also order an electrocardiogram (EKG) to check the electrical activity in your heart. 

There are four primary goals when treating low potassium levels: 

  • Reduction of potassium losses
  • Replenishment of potassium
  • Evaluation for potential toxicity
  • Determination of cause, to prevent future episodes

It is also essential to treat the underlying medical conditions or eliminate the cause. For example, if the overuse of laxatives causes hypokalemia, then addressing the physical or psychological need for laxatives should be part of the treatment plan. If a patient needs a diuretic, their doctor might discuss substitutions that allow potassium to remain in the body (potassium-sparing diuretic) or might prescribe daily potassium supplements. 

For people with extremely low potassium, a doctor might recommend intravenous treatment. 

What causes low potassium?

While potassium is a nutrient we get from food, diet alone rarely causes hypokalemia. There are several possible causes of hypokalemia and certain populations who have an increased risk of deficiency. These include:

  • Frequent vomiting or diarrhea (including from bulimia or laxative abuse)
  • Excessive sweating
  • Consuming too much alcohol
  • Poor nutrition and other nutritional deficiencies, such as magnesium or folic acid deficiency
  • Adrenal disorders, such as Cushing’s disease
  • Chronic kidney disease
  • Rare disorders, such as Liddle syndrome, Bartter’s syndrome, Gitelman syndrome
  • Leukemia
  • Inflammatory bowel disease
  • People with pica (especially if eating clay, as the clay binds potassium in the gastrointestinal tract and can cause increased potassium excretion)
  • People who take certain medications, such as diuretics

Medication-induced hypokalemia

Certain medications can also cause low potassium levels, including:

  • Diuretics: About 80% of people who take diuretics have a potassium deficiency due to an increase in urination. Diuretics, or “water pills,” may be prescribed to patients with high blood pressure, heart failure, and kidney disease. Diuretics are the most common cause of hypokalemia.
  • Laxatives: Laxatives can cause a loss of potassium in the stool.
  • Beta-adrenergic agonist drugs: Bronchodilators, steroids, or theophylline (used for asthma, emphysema, and COPD) can affect serum potassium and blood glucose levels.
  • Certain antibiotics: In large doses, some antibiotics can increase potassium excretion through the kidneys.
  • Insulin: Large doses of insulin, which may treat Hyperosmolar Hyperglycemic Nonketotic Syndrome (HHNS), a dangerous condition caused by very high blood sugar levels, are often supplemented with intravenous potassium.

Is low potassium dangerous?

Hypokalemia can contribute to, or cause other health issues, including: 

  • High blood pressure
  • Kidney stones
  • Decreased bone mineral density
  • Glucose intolerance with increased risk of developing type 2 diabetes
  • Urinary calcium excretion
  • Salt sensitivity 

Very low potassium levels can cause more severe health conditions, such as heart rhythm problems, and can cause your heart to stop.

RELATED: 13 signs of heart problems worth worrying about

How to raise potassium levels

In mild cases of hypokalemia, potassium levels can normalize within a few days after you start increasing potassium intake. Making sure you eat enough potassium-rich foods every day can help boost and maintain healthy potassium levels. The recommended daily potassium intake, according to the National Academies of Sciences, Engineering, and Medicine (NASEM) are:

  • Healthy adults: 3,400 mg per day for men, 2,600 for women (ages 19 years and older)
  • Teens ages 14 to 18 years old: 3,000 mg male, 2,300 mg female
  • Children ages 9 to 13: 2,500 mg male, 2,300 mg female
  • Children ages 4 to 8: 2,300 mg male, 2,300 mg female
  • Children ages 1 to 3: 2,000 mg for both male and female 
  • Babies ages 7 to 12 months: 860 mg for both male and female
  • Birth to 6 months: 400 mg for both male and female

Potassium-rich foods

The five foods highest in potassium levels are: 

Potassium-rich food Serving size Amount of potassium Percent daily value*
Dried apricots ½ cup 1,101 mg 32.3%-42.3%
Cooked lentils 1 cup 731 mg 21.5%-28.1%
Dried prunes ½ cup 699 mg 20.5%-26.8%
Mashed acorn squash 1 cup 644 mg 18.9%-24.7%
Raisins ½ cup 618 mg 18.1%-23.7%

* For adults

Other high-potassium foods include:

  • Baked potatoes
  • Kidney beans
  • Oranges/Orange juice
  • Soybeans
  • Bananas
  • Avocados
  • Bran
  • Carrots
  • Milk
  • Peanut butter
  • Salmon
  • Spinach
  • Tomatoes
  • Wheat germ

Potassium supplements

“The best way to raise potassium levels quickly is by taking a potassium supplement, many of which are available over-the-counter,” says Linda Girgis, MD, a board-certified family physician in private practice in South River, New Jersey. “Once the level reaches the normal level, you might be able to discontinue the supplements and maintain potassium levels through diet.”

Taking supplements, however, can be risky. Potassium supplements might cause minor gastrointestinal side effects or very high levels of potassium. 

“Having potassium levels too high can be just as dangerous as when they are too low. Either extreme can lead to cardiac arrhythmias and other problems,” says Dr. Girgis. “It is best to work with your doctor when taking supplements so that your potassium levels are monitored to ensure they are in the safe range.” 

Over-the-counter supplements might not be enough if your potassium level is extremely low. The FDA limits supplements to less than 100 mg of potassium, which is only a fraction of the daily recommended intake. Doctors can prescribe a more potent potassium supplement to patients with hypokalemia. 

There are also several different types of potassium supplements: 

It can be challenging to know what type is the best potassium supplement for you. “Potassium chloride is most commonly used for people who are potassium deficient,” according to Dr. Girgis,Potassium phosphate is useful if the patient is also phosphate deficient. If a patient is prone to kidney stones, potassium citrate might be helpful since the citrate can attach to the calcium in urine, preventing crystal formation.” She recommends seeking medical advice before taking any supplements.