How Does Diarrhea Cause Potassium Levels to Drop?

Man drinking electrolyte drink
Image Credit: StockWithMe/iStock/Getty Images

Diarrhea is the excessive loss of stool and fluids from the gastrointestinal tract. According to the National Digestive Diseases Information Clearinghouse, diarrhea means passing loose stools more than three times a day. Acute diarrhea usually goes away after a day or two, but chronic diarrhea usually lasts at least four weeks. Diarrhea can cause serious fluid and electrolyte disturbances, including lowering the body's potassium levels.

Facts About Potassium

Potassium is an electrolyte, or an electrically charged molecule important in many of the body's functions. According to the University of Maryland Medical Center, potassium is important for heart function, as well as having a significant role in muscle contraction and the digestive and nervous systems. The majority of potassium is stored within the cells, so changes in the small concentration of potassium in the bloodstream can potentially have serious health consequences. Potassium is also present in the fluids of the gastrointestinal tract, so illnesses that cause diarrhea can cause hypokalemia, or low potassium.


Diarrhea is a well-known cause of hypokalemia. Stomach acid has a high concentration of potassium, in the form of potassium chloride. Potassium is important in the stomach for the production and secretion of acid, which helps in the digestion of the foods we eat. When a person has diarrhea, the stomach contents get flushed out of the gastrointestinal tract into the stool and out of the body, taking with it a large amount of potassium and causing hypokalemia.

Symptoms of Low Potassium

A decrease in potassium levels may not cause any significant initial symptoms. According to the Merck Manuals Online Medical Library, as the potassium decreases, a person may experience muscle cramps and weakness, nausea and vomiting. Because of potassium's importance to the muscles, hypokalemia may cause tetany, or painful muscle spasms; rhabdomyolysis, a breakdown of muscle fibers that can clog up the kidneys and damage them; hypoventilation, or decreased ability to breathe; and paralytic ileus, or an inability of the intestines to move.


Rehydration, either oral or intravenous, is important for the treatment of diarrhea. Commercially available electrolyte-containing solutions are the best therapy for mild dehydration caused by diarrhea, as well as to prevent serious electrolyte imbalances, like low potassium. If a person is experiencing serious symptoms of potassium deficiency, intravenous potassium supplementation, in combination with intravenous fluids, may be necessary to prevent further complications.