Potassium is one of the body’s most important minerals. It is present in every cell of the human body. In solution -- as it is in the body -- potassium carries a positive electrical charge and is one of the body’s four main electrolytes along with sodium, chloride and bicarbonate. As an electrolyte, potassium plays a crucial role in water balance and the maintenance of blood pressure. Potassium is also important for normal muscle and nerve function as well as conduction of the electrical impulses that control the heart. Potassium deficiency -- known as hypokalemia -- can produce an array of symptoms, which vary in severity depending on the degree of deficiency.
Muscle Weakness, Spasms, Cramps and Tetany
In order for muscle cells to contract, a marked difference in intracellular and extracellular potassium concentrations must exist. As potassium levels drop, this concentration difference decreases and the muscles are unable to function normally. This causes generalized fatigue and a variety of muscular symptoms including weakness, spasms, twitching and cramps. In cases of extreme hypokalemia, the muscles can go into a sustained involuntary state of contraction called tetany.
Extreme hypokalemia can cause the muscles to go completely limp, a condition called flaccid paralysis. Importantly, the muscles involved in breathing can be affected by this condition, known as hypokalemic paralysis. Breathing can be slow and shallow, or may stop completely.
Muscle Stiffness, Aching and Tenderness
Severe potassium deficiency not only impairs the function of muscle cells, it also damages them, causing their contents to leak out -- a condition called rhabdomyolysis. Symptoms include profound weakness and muscle stiffness, aching and tenderness.
Abdominal Bloating, Pain and Cramping
The involuntary muscles of the stomach and intestines can also malfunction when the potassium level is too low. Symptoms including abdominal bloating, pain and cramping. Constipation may also occur. In the extreme, intestinal activity may virtually stop, a condition called paralytic ileus.
The rhythmic, coordinated contractions of the heart are controlled by electrical impulses, which are ferried across the heart muscle by a specialized conduction system. Hypokalemia can disrupt this conduction system, causing heart rhythm abnormalities. The most common symptom is heart palpitations -- an awareness of missed beats, extra beats, or a feeling that the heart is pounding too fast or too hard. These rhythm abnormalities can be life-threatening, and cardiac arrest may occur.
Dizziness and Fainting
Potassium deficiency can cause the kidneys to lose their ability to concentrate urine. As a result, excessive amounts of water are lost from the body and the blood pressure drops. This can cause symptoms of dizziness or fainting, especially when getting up to a standing position.
Frequent Urination and Extreme Thirst
As noted, hypokalemia can cause an excessive loss of water through the kidneys. Frequent urination and extreme thirst are common symptoms when hypokalemia has been present for some time.
Numbness and Tingling
Low potassium causes the nerves to fire abnormally, which may cause numbness, tingling or a burning sensation, especially in the hands and feet.
- Harrison’s Principles of Internal Medicine, 16th Edition; Anthony S. Fauci, M.D., et al.
- The Merck Manual Professional Edition: Hypokalemia
- Western Journal of Medicine: Hypokalemia as a Cause of Tetany