Low potassium (hypokalemia) refers to a lower than normal level of potassium in your bloodstream. Potassium is a chemical (electrolyte) that is critical to the proper functioning of nerve and muscles cells, particularly heart muscle cells.

Normally, your blood potassium level is 3.6 to 5.2 millimoles per liter (mmol/L). A very low potassium level (less than 2.5 mmol/L) can be life-threatening and requires urgent medical attention.

In most cases, low potassium is more commonly found by a blood test, before it gets so low that it causes symptoms.

Low potassium symptoms may include:

  • Weakness
  • Fatigue
  • Muscle cramps
  • Constipation

Abnormal heart rhythms (arrhythmias) are the most worrisome complication of very low potassium levels, particularly in patients with underlying heart disease.

Talk to your doctor about what your results mean. You may need to change a medication that's affecting your potassium level, or you may need to treat another medical condition that's causing your low potassium level. Treatment of low potassium is directed at the underlying cause and may include potassium supplements. Don't start taking potassium supplements without talking to your doctor first.

Aug. 17, 2011