Potassium is an electrolyte (mineral). It is needed for cells to function properly. You get potassium through food. The kidneys remove excess potassium through the urinary system to keep a proper balance of the mineral in the body.

Common causes of low blood potassium include:

• Medicines, such as diuretics (water pills), certain antibiotics (amphotericin B, chloroquine at toxic levels)
• Diarrhea or vomiting
• Eating disorders (such as bulimia)
• Hyperaldosteronism
• Laxative overuse, which can cause diarrhea
• Chronic kidney disease
• Low magnesium level
• Sweating
• Genetic disorders, such as hypokalemic periodic paralysis, Bartter syndrome

A small drop in the blood potassium level often does not cause symptoms or causes mild to moderate symptoms, which may include:

• Constipation
• Feeling of skipped heart beats or palpitations
• Fatigue
• Muscle damage
• Muscle weakness or spasms
• Tingling or numbness

A large drop in the blood potassium level may lead to abnormal heart rhythms, especially in people with heart disease. This can cause you to feel lightheaded or faint. A very low blood potassium level can even cause your heart to stop.

Your health care provider will order a blood test to check your potassium level. Normal range is 3.7 to 5.2 mEq/L (3.7 to 5.2 mmol/L).

Other blood tests may be ordered to check levels of:

• Glucose, magnesium, calcium, sodium, phosphorous
• Thyroid hormone
• Aldosterone

An electrocardiogram (ECG) to check the heart may also be done.

If your condition is mild, your provider will likely prescribe oral potassium pills. If your condition is severe, you may need to get potassium through a vein (IV).

If you need diuretics, your provider may:

• Switch you to a form that keeps potassium in the body. This type of diuretic is called potassium-sparing.
• Prescribe extra potassium for you to take every day.

Eating foods rich in potassium can help treat and prevent low level of potassium. These foods include:

• Avocados
• Baked potato
• Bananas
• Bran
• Carrots
• Cooked lean beef
• Milk
• Oranges
• Peanut butter
• Peas and beans
• Salmon
• Seaweed
• Spinach
• Tomatoes
• Wheat germ

Taking potassium supplements can usually correct the problem. In severe cases, without proper treatment, a severe drop in the blood potassium level can lead to serious heart rhythm problems that can be fatal.

In severe cases, life-threatening paralysis may develop, such as with hypokalemic periodic paralysis.

Call your provider right away if you have been vomiting or have had excessive diarrhea, or if you are taking diuretics and have symptoms of hypokalemia.

Potassium - low; Low blood potassium; Hypokalemia

Mount DB. Disorders of potassium balance. In: Yu ASL, Chertow GM, Luyckx VA, Marsden PA, Skorecki K, Taal MW, eds. Brenner and Rector's The Kidney. 11th ed. Philadelphia, PA: Elsevier; 2020:chap 17.

Seifter JL. Potassium disorders. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 109.

Updated by: Jacob Berman, MD, MPH, Clinical Assistant Professor of Medicine, Division of General Internal Medicine, University of Washington School of Medicine, Seattle, WA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.