Your body uses several mechanisms to keep fluids and chemicals in proper balance. If you are otherwise healthy, your body can usually bring small and even moderate shifts in potassium back into line without you being aware of the fluctuation. However, if your potassium level gets very high or low, symptoms may develop that affect your muscles, heart and nerves. Severe potassium level abnormalities are potentially life threatening.
Your muscles, including the heart, need potassium to function. Potassium works in conjunction with sodium, magnesium and calcium in muscle cells to generate the electrical signals that stimulate movement. With hyperkalemia, potassium levels are too high, and electrical impulses in the muscle cells slow down. In skeletal muscle -- muscles that move bones -- this can cause weakness and, in rare cases, paralysis. Very high potassium levels can cause the heart's conduction of its electrical signal to slow down, resulting in an abnormal heart rhythm called an arrhythmia. In some cases, a severe arrhythmia can occur, and the heart rhythm can become totally erratic. With such rhythms, the heart becomes ineffective at pumping blood.
Hyperkalemia Heart Symptoms
If your potassium level is only slightly elevated, you are unlikely to experience any symptoms. Even with higher levels, symptoms may be vague and nonspecific. However, as your levels rise, an electrocardiogram test may show specific signs that your heart’s electrical signal is abnormal. You might experience palpitations -- the feeling of an irregular heartbeat -- dizziness or loss of consciousness if your heart slows significantly. In rare cases, the heart may stop beating entirely.
Hyperkalemia Muscle Symptoms
Skeletal muscle symptoms of hyperkalemia might include weakness that starts in your legs and moves up to the trunk and then to the arms. People with muscle weakness from hyperkalemia usually remain alert, unless they develop a heart rhythm abnormality that reduces blood flow to the brain. Symptoms abate when potassium levels are brought back to normal with treatment.
Low potassium, or hypokalemia, may contribute to other problems, including low blood magnesium levels, high blood pressure and resistance to insulin, which can cause higher blood sugars. Low potassium can affect the heart’s ability to maintain a normal electrical signal. It may also cause heart muscle cells to take too long to reset themselves after contracting. This can lead to dangerous arrhythmias, especially if you already have heart disease.
Mild or moderate hypokalemia is unlikely to cause symptoms. However, low potassium can cause some of the same symptoms caused by high potassium. An electrocardiogram will show electrical conduction problems specific to hypokalemia, such as an irregular or slow rhythm or extra heartbeats. You may experience palpitations or generalized weakness. With a severely low potassium level, your heart may stop beating. In muscles, hypokalemia can cause weakness or paralysis. Severe muscle weakness may lead to difficulty breathing. Other possible symptoms include numbness, tingling and muscle cramps. Rhabdomyolysis -- muscle damage from breakdown of muscle cells -- can also occur in some people with hypokalemia.